The Definitive Guide to Blood Sugar

blood sugarWhat’s sweet, red, sticky, and deadly?

Blood sugar. (I’m sure there are other things that qualify, but most of them contain sugar of some sort so I’m sticking with it.)

Too little of it, and you go into hypoglycemic shock. That can kill you if left untreated.

Too much of it, and you waste away slowly. Chronic overexposure to sugar will degenerate your tissues and organs.

Yes, getting blood sugar right is extremely important. Vital, even.

Today, I’m going to explain how and why we measure blood sugar, what the numbers mean, why we need to control it, and how to maintain that control.

First, blood sugar is tightly controlled in the body. The average person has between 4-7 grams of sugar circulating throughout their body in a fasted state—that’s around a teaspoon’s worth. How does that work when the average person consumes dozens of teaspoons in a single day?

Again, it’s tightly controlled.

The majority of the sugar “in our system” is quickly whisked away for safekeeping, burning, or conversion. We store as much of it as glycogen in our liver and muscle as we can. We burn some for energy. And, if there’s any left over, we can convert it to fat in the liver.

But sometimes, sugar lingers. In diabetics, for example, blood sugar runs higher than normal. That’s actually how you identify and diagnose a person with diabetes: they have elevated blood sugar.

There are several ways to measure blood sugar.

  • The basic finger prick: Prick your finger, produce a few drops of blood, place blood on test insert, test blood sugar level. It’s the most common method.
  • Fasting blood sugar: Your blood sugar level when fasted. These tests are usually taken first thing in the morning, because that’s the only time most people haven’t eaten in the last few hours. “Normal” is under 100.
  • Postprandial blood sugar: Your blood sugar after eating. These tests measure your blood sugar response to food; they also measure your ability to dispose of blood glucose.
  • HbA1C: Average blood sugar over 2/3 months. HbA1c measures the degree of glycation of your red blood cells’ hemoglobin; this is an indirect measure of how much blood sugar your cells are exposed to over time, since a red blood cell that’s exposed to more sugar in the blood over its life cycle—2-3 months—will have more glycation. Thus, A1c seeks to establish the average level of blood sugar circulating through your body over the red blood cell’s life cycle, rather than track blood sugar numbers that rapidly fluctuate through the day, week, and month. It’s a measurement of chronic blood sugar levels, not acute.
  • The continuous glucose monitor: A wearable device that measures your blood sugar at regular intervals throughout the day and night. This is becoming more common. The beauty of the CGM is that you get a visual display of blood sugar’s rise and fall throughout the day in response to meals, workouts, fasts, stress, etc. Since elevated blood sugar does its damage over the long term, seeing the entire daily trend is more illuminating than taking single snapshots with a finger prick. It’s similar in power to HbA1c, only with greater accuracy.

What’s Normal?

According to the American Diabetes Association, any fasting blood sugar (FBG) under 100 mg/dl is completely normal. It’s safe. It’s fine. Don’t worry, just keep eating your regular diet, and did you get a chance to try the donuts in the waiting room? They only start to worry at 110-125 (pre-diabetic) and above 125 (diabetic).

This may be unwise. Healthy people subjected to continuous glucose monitoring have much lower average blood glucose—89 mg/dl. A 2008 study found that people with a FBG of 95-99—still “normal”—were 2.33 times more likely to develop diabetes in the future than people on the low-normal end of the scale.

As for postprandial blood glucose, the ADA likes anything under 140 mg/dl.

How about HbA1c? A “normal” HbA1c is anything under 5.7. And 6.0 is diabetic. That’s what the reference ranges, which mostly focuses on diabetes. What does the research say? In this study, under 5 was best for heart disease. In this study, anything over 4.6 was associated with an increased risk of heart disease.

That 5.7 HbA1c isn’t looking so great.

What’s “normal” also depends on your baseline state.

Healthy FBG depends on your BMI. At higher FBG levels, higher BMIs are protective. A recent study showed that optimal fasting blood glucose for mortality gradually increased with bodyweight. Low-normal BMIs had the lowest mortality at normal FBG (under 100), moderately overweight BMIs had the lowest mortality at somewhat impaired FBG (100-125), and the highest BMIs had the lowest mortality at diabetic FBG levels (over 125).

If you’re very low-carb, postprandial blood glucose will be elevated after a meal containing carbs. This is because very low-carb, high-fat diets produce physiological insulin resistance to preserve what little glucose you have for the tissues that depend on it, like certain parts of the brain. The more resistant you are to insulin, the higher your blood glucose response to dietary glucose.

HbA1c depends on a static red blood cell lifespan. A1c seeks to establish the average level of blood sugar circulating through your body over the red blood cell’s life cycle, rather than track blood sugar numbers that rapidly fluctuate through the day, week, and month. If we know how long a red blood cell lives, we have an accurate measurement of chronic blood sugar levels. The clinical consensus assumes the lifespan is three months. Is it?

Not always. The life cycle of an actual red blood cell differs between and even within individuals, and it’s enough to throw off the results by as much as 15 mg/dl.

Ironically, people with healthy blood sugar levels might have inflated HbA1c levels. One study found that folks with normal blood sugar had red blood cells that lived up to 146 days, and RBCs in folks with high blood sugar had life cycles as low as 81 days. For every 1% rise in blood sugar, red blood cell lifespan fell by 6.9 days. In those with better blood sugar control, RBCs lived longer and thus had more time to accumulate sugar and give a bad HbA1c reading. In people with poorer blood sugar control, red blood cells live shorter lives and have less time to accumulate sugar, potentially giving them “better” HbA1c numbers.

Anemia can inflate HbA1c. Anemia depresses the production of red blood cells. If you have fewer red blood cells in circulation, the ones you do have accumulate more sugar since there are fewer cells “competing” for it. Anemia isn’t anything to sniff at, but it does throw off HbA1c.

Hyperglycemia and Health

Okay, is hyperglycemia actually a problem? I’ve heard some suggest that hyperglycemia is a marker of poor metabolic health, but it’s not actually causing anything bad itself. I agree with the first part—hyperglycemia indicates poor metabolic health and is a risk factor for things like heart disease and early mortality—but not the last. Indeed, hyperglycemia is both an effect and direct cause of multiple health issues.

Most cell types, when faced with systemic hyperglycemia, have mechanisms in place to regulate the passage of glucose through their membranes. They can avoid hyperglycemic toxicity by keeping excess sugar out. Other cell types, namely pancreatic beta-cells, neurons, and the cells lining the blood and lymphatic vessels, do not have these mechanisms. In the presence of high blood sugar, they’re unable to keep excess sugar out. It’s to these three types of cells that hyperglycemia is especially dangerous.

Unfortunately, these are all pretty important cells.

What happens when too much glucose makes it into one of these cells?

Reactive oxygen species (ROS) generation is a normal byproduct of glucose metabolism by the cell’s mitochondria. If the stream of glucose into the cell is unregulated, bad things begin to happen: excessive ROS, a mediator of increased oxidative stress; depletion of glutathione, the prime antioxidant in our bodies; advanced glycation endproduct (AGE) formation; and activation of protein kinase C, a family of enzymes involved in many diabetes-related complications. It’s messy stuff.

How does this play out in the specific cell types that are susceptible, and what does it mean for you?

Pancreatic beta-cells: These cells are responsible for secreting insulin in response to blood glucose. They essentially are the first line of defense against hyperglycemia. If maintained for too long or too often, hyperglycemia inhibits the ability of pancreatic beta-cells to do their job. For instance, type 2 diabetics have reduced pancreatic beta-cell mass; smaller cells have lower functionality. Mitochondrial ROS (often caused by hyperglycemia) also reduce the insulin secreted by the cells, thereby reducing their ability to deal with the hyperglycemia and compounding the initial problem.

Neurons: The brain’s unique affinity for glucose makes its glucose receptor-laden neuronal cells susceptible to hyperglycemia. It simply soaks up glucose, and if there’s excessive amounts floating around, problems arise. Hyperglycemia is consistently linked to cognitive impairment, causes the shrinking of neurons and the inducement of spatial memory loss, and induces neuronal oxidative stress. It also impairs the production of nitric oxide, which is involved in the hippocampus’ regulation of food intake.

Endothelial cells: Flow mediated dilation (FMD) is the measure of a blood vessels’ ability to dilate in response to increased flow demands. Under normal conditions, the endothelial cells release nitric oxide, a vasodilator, in response to increased shear stress. Under hyperglycemic conditions, nitric oxide release is inhibited and FMD reduced. A decreased FMD means your endothelial function is compromised and may cause atherosclerosis (PDF).

Electrolyte depletion: Persistent hyperglycemia can cause the body to shed glucose by urinating it out. In doing so, you also end up shedding electrolytes.

Okay, okay. Controlling your blood sugar is important. Avoiding hyperglycemia is one of the most important things you can do for your health and longevity. How do I do it?

How to Improve Blood Sugar

  • Go for a walk. A short walk after eating will reduce blood sugar. Fifteen minutes is probably enough (although more is always better).
  • Eat vinegar before. Eating vinegar before a meal that contains carbohydrates will improve the blood glucose response to that meal.
  • Exercise. Exercise depletes muscle glycogen, which opens up storage depots for incoming glucose. If glucose is converted to glycogen and deposited in your muscles, your blood glucose will normalize. Pretty much any kind of exercise works.
    • Sprint and/or intervals. A review looked at the blood glucose responses of diabetics (type 1 and type 2) to “brief high intensity exercise,” as which sprinting definitely qualifies, finding that although glucose was elevated immediately post workout, blood glucose control is improved for one to three days following a sprint session. Research finds that endurance training works, too, but sprinting may work faster and better.
    • Steady state endurance. Then again, steady state endurance training was just as effective as sprinting at reducing glucose variability and improving glucose spikes in overweight women. There was no difference between the two—both beat doing nothing.
    • Resistance training.
    • All of the above. As different types of training target different tissues, deplete glycogen at different rates, and induce different metabolic effects, doing sprints, weights, and low level aerobic activity is your best bet for improving glucose control.

When I take a bird’s eye view of all this, the best glucose-lowering exercise is the one you’ll do on a regular basis. It’s all good.

  • Avoid unnecessary carbohydrates. Carbs you earn through glycogen-depleting exercise will not contribute to hyperglycemia. Those are “necessary,” or at least “earned.” Carbs you didn’t earn will contribute to hyperglycemia. A surefire way to avoid hyperglycemia is to avoid the foods that induce it—carbs.
  • Eat more protein and fat, fewer carbs. This is a simple one for most of you guys, but many people never consider it. A basic swap of whole eggs (or egg whites) for carbs reduces not just postprandial glycemia but also endothelial dysfunction.
  • Get enough sleep. Sleep deprivation increases blood glucose variability and impairs regulation.
  • Eat fermented dairy. Kefir improves glycemic control in patients with type 2 diabetes. Yogurt does too. Cheese is also associated with better glucose control.
  • Use spices. Spices can have profound anti-hyperglycemic effects.

If you’re low-carb or keto and need to pass a glucose tolerance test, eat 150-250 grams of carbs per day in the week leading up to the test. This will give you a chance to shift back into sugar-burning mode.

Long Term Blood Glucose Control?

Consistency is everything. Consistently doing all the little tips and hacks we just went over that lower blood sugar in the moment will lead to long term blood sugar control. If you take vinegar before and walk after every single meal for the rest of your life, you will control postprandial blood sugar. If you avoid excess carbohydrates, you will exert long-term control over blood sugar levels. If you exercise 3-4 times a week and get plenty of low-level activity, you’ll be much less likely to have hyperglycemia.

Thus concludes the Definitive Guide to Blood Sugar. If you have any questions or comments, drop them in down below. Thanks for reading!


Adams RJ, Appleton SL, Hill CL, et al. Independent association of HbA(1c) and incident cardiovascular disease in people without diabetes. Obesity (Silver Spring). 2009;17(3):559-63.

Lee EY, Lee YH, Yi SW, Shin SA, Yi JJ. BMI and All-Cause Mortality in Normoglycemia, Impaired Fasting Glucose, Newly Diagnosed Diabetes, and Prevalent Diabetes: A Cohort Study. Diabetes Care. 2017;40(8):1026-1033.

Virtue MA, Furne JK, Nuttall FQ, Levitt MD. Relationship between GHb concentration and erythrocyte survival determined from breath carbon monoxide concentration. Diabetes Care. 2004;27(4):931-5.

Das evcimen N, King GL. The role of protein kinase C activation and the vascular complications of diabetes. Pharmacol Res. 2007;55(6):498-510.

Guillausseau PJ, Meas T, Virally M, Laloi-michelin M, Médeau V, Kevorkian JP. Abnormalities in insulin secretion in type 2 diabetes mellitus. Diabetes Metab. 2008;34 Suppl 2:S43-8.

Sakai K, Matsumoto K, Nishikawa T, et al. Mitochondrial reactive oxygen species reduce insulin secretion by pancreatic beta-cells. Biochem Biophys Res Commun. 2003;300(1):216-22.

Malone JI, Hanna S, Saporta S, et al. Hyperglycemia not hypoglycemia alters neuronal dendrites and impairs spatial memory. Pediatr Diabetes. 2008;9(6):531-9.

Kawano H, Motoyama T, Hirashima O, et al. Hyperglycemia rapidly suppresses flow-mediated endothelium-dependent vasodilation of brachial artery. J Am Coll Cardiol. 1999;34(1):146-54.

Winding KM, Munch GW, Iepsen UW, Van hall G, Pedersen BK, Mortensen SP. The effect on glycaemic control of low-volume high-intensity interval training versus endurance training in individuals with type 2 diabetes. Diabetes Obes Metab. 2018;20(5):1131-1139.

Rafiei H, Robinson E, Barry J, Jung ME, Little JP. Short-term exercise training reduces glycaemic variability and lowers circulating endothelial microparticles in overweight and obese women at elevated risk of type 2 diabetes. Eur J Sport Sci. 2019;19(8):1140-1149.

Mcdonald JD, Chitchumroonchokchai C, Li J, et al. Replacing carbohydrate during a glucose challenge with the egg white portion or whole eggs protects against postprandial impairments in vascular endothelial function in prediabetic men by limiting increases in glycaemia and lipid peroxidation. Br J Nutr. 2018;119(3):259-270.

Daza EJ, Wac K, Oppezzo M. Effects of Sleep Deprivation on Blood Glucose, Food Cravings, and Affect in a Non-Diabetic: An N-of-1 Randomized Pilot Study. Healthcare (Basel). 2019;8(1)

Watanabe D, Kuranuki S, Sunto A, Matsumoto N, Nakamura T. Daily Yogurt Consumption Improves Glucose Metabolism and Insulin Sensitivity in Young Nondiabetic Japanese Subjects with Type-2 Diabetes Risk Alleles. Nutrients. 2018;10(12)

Comerford KB, Pasin G. Emerging Evidence for the Importance of Dietary Protein Source on Glucoregulatory Markers and Type 2 Diabetes: Different Effects of Dairy, Meat, Fish, Egg, and Plant Protein Foods. Nutrients. 2016;8(8)

Thondre PS. Food-based ingredients to modulate blood glucose. Adv Food Nutr Res. 2013;70:181-227.

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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48 thoughts on “The Definitive Guide to Blood Sugar”

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  1. Great article Mark! T1 diabetic and physician here. I’m sharing this article on my page.

    I stress a low carb diet and tight control of blood sugars like you mention in the article. I wish the standard of care for diabetes took the points you make here into consideration. But sadly this is not the case.

    I’ve been eating a low carb diet for over a decade. My last a1c was 4.8%. My CGM usually has my blood sugar average in the 80s, with a very low standard deviation (usually around 20). SD is a great measurement on the CGM to ensure blood sugars aren’t roller coastering despite a good average.

    No signs of any complications for me, and I’ve had diabetes for 13 years. Most diabetics at this point would have at least early signs of retinopathy, neuropathy, and especially autonomic neuropathy (which leads to gastroparesis making diabetes management even harder!).

    Thanks for all you do Mark!

    1. I agree the Primal diet is the best I’ve seen for Diabetics, its changed my life.

      PS Dr Attar I’m Type 1 for 12 years and any A1C under 5 is dangerous. 4.8 is lower than someone without T1. In my Endo’s practice he tells me that with over 1000 patients I am by far his healthiest diabetic (Most are T2 of course) and my A1C runs around 6to 6.5.

      1. Under 5 means an average blood sugar in the 80s. In what way is this dangerous? Average blood sugar in the 80s plus low standard deviation means very stable and flat lined blood glucose and is the healthiest one could be. With low standard deviation it means both hyper and hypo glucemias are rare.
        In what way would higher glucose be healthier?

        1. Hey Dr. Attar,
          I’ve been a type 1 diabetic for 23 years. No complications and I’ve been eating a LC diet 6 months of diagnoses. My last A1C was 4.7. Kevin is confused by his Endocrinologist. Most will not advise such a low A1C for fear the diabetic in their care will have a low that causes complications. And then they might be sued.
          Sad, but that is the reality.
          Obviously, I’ve been following Dr. Bernstein’s plan since I found his book in 1997.
          23 years LC , and no complications? We must be doing something right. And yet, we still have guys like Kevin not getting it.
          Mark, a great article. Lots of good advice. this works for Type 1’s as well as type 2’s. The difference with us Type 1’s is, if we don’t have consistency, as you said, things go wrong very quickly. So,l the thing to do for us is eat the same amount for every meal. For me, that’s 6 grams of carbs for breakfast, 12 for lunch and 12 for dinner. Then the injections can help maintain a “normal” blood sugar around the clock. Hence, a 4.7 A1C.
          To reiterate the A1C info: According to Dr. Bernstein, not the ADA, a normal A1c is between 4.4 and 4.6. He has more than 10,000 tests from his patients over the years. I would count him as the foremost authority on Diabetes in the world today. Not to take anything from you Dr. Attar.

          Regards and keep up the good work. Fight the good fight and all that.

        2. Hi Dr Attar,
          Well I was obviously told wrong by my Endo, which doesn’t surprise me since I’m super healthy and he wanted to start me on a statin because I’m a T1 and 40 LOL. My Mistake.

          Is that 4.8 following the primal diet? I’m curious your diet and routine. I’ve never gotten my A1C below 6 and would love too. I wear the Dexcom which is helpful and use the omnipod pump.

          1. Kevin,
            I achieve under 5.0 a1c vía low carb and using principles from Dr Richard Bernstein (t1 doc, in his 80s, also blood sugars and A1c in this range). Mark Sisson’s Primal principles are compatible with this.
            Check out Bernstein’s book Diabetes Solution or his YouTube channel Diabetes University.
            You should definitely question an A1c in the 6s. This is abnormal and in the diabetic range.
            Diabetics are entitled to healthy, non diabetic blood sugars and A1c. If you’re endo is telling you 6s is healthy, should maybe look into another.

  2. I’m very ill with chronic Lyme disease. Because of my illness I’m not able to do any exercise, including walking 15 minutes.
    My question is: would an infrared sauna session of 60 minutes at a temp of 140-146 work on the body the same way exercise works in this blood sugar article you recommend?

    1. From what I’ve learned, the sauna can really help. Check with Rhonda Patrick for more info on saunas. Or Ben Greenfield.

      I have Lymes. Do whatever you can to keep moving, it makes a huge difference. Work on your sleep anyway you can.
      Look into Stephan Buhner’s books and protocols,which vary according to symptoms and co-infections.

    2. Hi Michelle,
      I infrared sauna at 149F for an hour most days. I monitor my heart rate. Last July, my heart rate was 140bpm. Now, it is generally 110bpm. 72 years old male.
      Perhaps you could increase your sauna sessions over time while monitoring your blood glucose.
      Best wishes

      1. Jim, any suggestions for saunas? I was all set to buy a Costco one, but then I read that the cheaper saunas might be bad for you due to lack of EMF shielding and use of cheaper materials.

    3. Michelle. Google Joe and Charlene Andersen. You’ll find her story very helpful.

  3. I eat very low carb,exercise and my morning BS is always averaging 115,so I think this hasn’t been evaluated correctly for normal people .

    1. Floyd, I have the same situation as you do and my diet and exercise is similar to yours. My morning blood sugar is usually in the 110 to 120 range, but my a1C readings have been below 5 for the last two years. To me, the two readings don’t mesh. I have thallasemia minor and I’m not sure if that has something to do with these readings.

      1. Same here. I have eaten a low carb diet for years, and my fasting blood glucose is always around 105-108. I used to worry about it, but I don’t anymore. Google the “dawn effect” and you will see that in some people (me included), the body simply boosts blood glucose before you awake in the morning to prepare for awakening and activity. This will happen (for me, and many others) regardless what kind of diet you eat or the amount of exercise you get. My A1c has always been pretty good (5.2 or so), so that tells me that my blood glucose is basically under control.

        1. Mine was 113 for years and is now 95 regularly. I was eating primal, but it didn’t lower the fasting blood sugar, although it lowered my triglycerides from 285 to 135 after a year as a vegan. Not only is my FBS 95, my triglycerides are now in the mid 60s! I’m eating the Plant Paradox diet, which is close to vegan and I really believe that has done the trick. So no grains and if I eat foods containing lectins I prepare them properly (so as to remove the majority of them). I have super high energy all day, less hair loss, my family says my hair is getting darker (less gray), my stamina has improved, and my body doesn’t ache for the first 10 miles of my 20-50 mile bicycle rides like it used to.

    2. I’d bet a dollar you are experiencing “dawn phenomena.” I can’t remember which of the blogging doctors notes that his low carb diet, long term, often has FBG’s of… as I recall…..110-115. Yet his A1C is very low.

      Exercise’s effect on insulin is pretty low compared to diet. Especially when at an an appropriate body weight w/o too much fat. My A1C over the years pretty much tracks what I weighed at the time.

      Check you blood sugar at 3AM. You will almost certainly be pleasantly surprised. I’ve seen about a 20 point difference between then and 4 or 5 hours later.

      I don’t recall the theories offered up for that.

  4. I’m asking for your assessment of my blood sugar situation and any suggestions. I’ve knowingly been battling high blood sugar for maybe 8 years or so and I’m 72. At a routine general physical a FBG came up at 185. I was threatened with medication (yikes) and allowed a time to try to correct it myself. I bought the Blood Sugar Solution and began with a bit of improvement, then moved to the New Atkins of about 50 Grams of carbs a day with a bit more improvement (maybe down to 125 to 145). Then Dr. Adam Nally said I had to be below 20 grams a day to get blood glucose down. I strictly complied lost a little weight but still maintained the muffin top, got the FBG down to 80 to 120 ish. I followed this for a little over 2 years. During that time I had difficulty sleeping, had the most severe nearly constant muscle cramps imaginable, was extremely constipated and a few other negative things. I finally decided to add back more carbs and everything improved except the blood sugar crept back up. I did take more electrolytes with tons of magnesium, mountain walks 2 to 7 times a week. (I live at 9500’, so it’s brisk with huffing and puffing). I was stressed mostly with work and as I said I wasn’t sleeping. Now here I am 72, mostly retired, not as stressed, blood sugar often 180 to 200, still avoiding medication and desperate for a solution. I never have a huge drop in blood sugar. It’s the highest in the AM. I feel dizzy if it spikes higher. I’m not very big on docs, thinking they are mostly puppets of big pharma. There’s a lot more, but for the sake of brevity I’ll end. I would be delighted to answer questions or discuss anything. I continue to believe that diet and lifestyle can be the solution to good health, if only I can find the right formula! I’m very interested in Your thoughts.

    1. Hi DiAnn. Check out The Peoples Chemist website. He has a product called Cinnergy that people say is the greatest. I take it myself. Hope this helps.

      1. Am in the process of checking the site out now. Thank you bunches for the suggestion to Diane.

    2. Check out Dr Attar’s website and the one he recommends Dr Bernstein’s. It sounds like they are going in the right direction and may have some points there?

    3. Check out Dr. Jason Fung’s work with intermittent fasting. Lots of YouTube videos and he’s written a couple of books.

    4. Hi Diann, those are serious numbers, like organ damage serious. See Bloodsugar101 website by Jenny Rush. Check your A1c and Fructosamine. Are they in normal range or not? Try strength training and building some muscle mass (you will need high protein). You may want to rethink the DR., but go for one that uses lifestyle first. Don’t wait until you have serious damage.

    5. IF and extended fasts along with Keto. Months of it. It’s not a quick fix.
      Eat Like a Bear FB group is having insane success with HUGE daily salads, mostly lettuces. No pills, no potions, just commonsense in a framework that is effective—along with community support. All free, yes. Meat, dairy encouraged but there are ppl trying to be vegheads in there.
      Older women losing 100#. Severe diabetics overcoming their disease AND losing weight. Simple method. Check it out!

      1. You may also want to check out Mastering Diabetes. They have had great success improving and reversing Diabetes Type 2.

  5. Great information Mark, thank you. What about hypoglycemia while fasting >36-48 hours. During a 3 day fast I monitor BS and ketones numerous time in that fasting state as my sugar has dropped to 56 and below after as little as 36 hour fasting. I do consume bullet proof coffee once a day in this fasting period. When it reaches 56 I consume fat. What’s up with this and how can I achieve autophagy if I can’t maintain the fast for 3 days at least.

    1. Piggybacking on this comment… loved the article but disappointed there was no mention of hypOglycemia. I don’t get hyper symptoms but depending on what I eat, exercise, etc., my body over-produces insulin which drops my blood sugar into sometimes very scary-low numbers. This is reactive hypoglycemia, which many doctors — including endocrinologists know very little about.

    2. Same – HypO. I am always wondering what ‘blood sugar control’ advise applies to me since I have an opposite problem. I have a high Ha1c that has always confused me. (5.6-5.9) I don’t have high blood sugar spikes, but instead fall way low. (not overweight) The more low-carb I go, the higher my Ha1c. Your paragraph on longer lived blood cells is a possible answer for me. I think I need more whole food carbs than a hypEr type.
      I really appreciate your website and have for many years now. As always, I sort through the info and use what applies to me but the solution to this low blood sugar issue has eluded me. And searches online haven’t been much help either. Appreciate all you do for sharing important info with the rest of us. Hoping more in-depth HypO info will be on your discussion list! 🙂

  6. What does « anemia isn’t anything to sniff at » mean?

    1. It sucks. Big time. I have caused it for myself with too many blood donations. It’s nothing to take lightly in its own right. I’m still straightening mine out, 20 months after my last donation. At least mine seems to be curable. I feel for the guys stuck with it forever.

      Oh, and I also had it in a really big way 13 years ago, during my 4 years as a vegan.

  7. Mark – Great article. After reading it I think the logical follow-up is on the topic of fasting insulin…causes, health impacts, etc. I recently discovered, after some time on a LCHF diet, that despite normal A1C and FBG levels, my fasting insulin was 2x normal levels. Interestingly the elimination of dairy resolved the issue in the two months between blood tests. Fasting insulin is rarely tested by conventional doctors and to my understanding is a risk factor for CAD. Seems worth delving into.

    1. Mark, I second Gary’s thoughts although I have had a different personal experience. I would like to learn more about what fasting insulin numbers mean for a Pre-T2 Diabetic and what should one do to properly control ones fasting insulin. Question: Is Gary’s experience that his eliminating dairy resolved his problem of greatly elevated fasting insulin to be expected, unusual or unknown?

  8. Mark: “Too little sugar and you go into hypoglycemic shock”…then nothing on hypoglycemia after that. Why? I was HYPO before turning Primal and haven’t looked back, but it would be nice to hear more about HYPO. Is it not important? I think thousands out there have Hypo and not Hyper.


  9. Having gone low-carb in mid-December I am actually having the opposite problem. I an non-diabetic but have about 80 pounds to lose.

    As soon as I dropped the carbs for protein/fat my blood sugar (per CGM) runs steady between 55 and 70 (down from 80 – 150 on regular SAD.

    Dr. Google seemed to say that I should go to the hospital for hypoglycemia but I feel fine, no headache, nausea, shakiness…so I’m just going to keep on unless that happens. 12 pounds lost so far!

  10. Great post Mark. Thank you.

    One other thing to consider with the A1c is that the test isn’t truly standardized. Results from different labs can vary by nearly close to a full point.

    I also have been trying to learn WHY A1cs can go so off kilter after or while being sick or carrying an untreated infection.

  11. “If we know how long a red blood cell lives …”

    But we don’t so we use an average. My fasting glucose always measures right at about 80. My A1c is about 5.6. I eat very little carbs. So, I don’t stress out about my A1c, at a certain point the worry and stress about every biometric can be detrimental to your health I think. 🙂 But … you also don’t want to bury your head in the sand, and good suggestions by Mark, thanks for the reminders.

  12. Hello Mark, This is an excellent article. However, in the lead off a person is shown testing his sugar with a glucose monitor with a readout of 51. This is approaching unresponsiveness and is very unlikely that a person would be able to even test his own blood sugar at this level. More likely, a result of 78-88 would be more accurate. Thank you, Julia RN

    1. Hi Julia,
      Good point. It is low, but not too low for me as a type 1. 51 is easy to come back from for a Type 1 who eats low-carb. (Dr. Bernstein’s plan.) Not fun, but manageable. In 23 years, I’ve never been unresponsive, but i’m in much better shape than the “average” Type 1.
      Still, good catch on that 51. Strange he’d put that up. Maybe that was the point, see if anyone was paying attention to his pics. LOL!

    2. Maybe my glucose monitor is off, but I struggle with hypO and just recorded a 51 last week. That reading came about 2 1/2-3 hours after a snack of about 2 tbls almond butter – no sweetener. I can feel when it starts to drop – coolness in my head/neck, weakness, sometimes shaky and panicky for something to eat. Fasting BS is usually around 75 in mornings. Since that ultra low reading I have added more carbs back in because clearly (even if my glucometer is not accurate – whatever the number – it is way to low because of physical symptoms). Anyway, I think there is probably a lot more like me out there so hoping more info on hypO will be upcoming.

  13. My doctor proposes that the Personal Fat Threshold (PFT) affects the appearance of metabolic syndrome, including T2D. At a certain body fat level, different for each of us but for me it was about 25% body fat, fat spills out of fat cells and accumulates in the liver and the pancreas. This visceral fat covers beta cells, inhibiting function and results in rising blood sugar levels.

    The problem can be reversed by losing visceral fat, by diet, fasting, and exercise. Even diagnosed diabetics can regain beta cell function by removing the fat that is plugging their pancreatic fat. I reversed prediabetes by losing enough fat to get down to 16-18% body fat (63 year old male).

    I have seen recent clinical research papers that describe this pathology, so it’s not just an internet rumor. The PFT model fits with my experience.

  14. Insulin Rate is also important, perhaps even more of HBAc1, but no one quoted it. Isn’t that right?

  15. Hi Mark,
    This was so helpful, thank you so much. I especially was helped by your comments on how A1C works.

    My question is from this statement you made…As for postprandial blood glucose, the ADA likes anything under 140 mg/dl”…you left me hanging there. Any further comments on this position. By implication you are suggesting that this is far too lenient. My own research on this urges people to keep postprandial blood sugar rises to no more than 20 mg/dl of your fasting number (which is hopefully in the 80’s). I got that from the venerable Dr. Bernstein. I have also heard from other sources that any rise over 100 mg/dl is detrimental.

    I would love to hear what you think about postprandial numbers!

  16. Whoa, I’m fascinated at the statement that “at higher FBG, higher BMI is protective.” So obese people can have higher fasting blood glucose levels but lower mortality? Mark, can you elaborate?

    (And for the love of god and middle-aged eyes, can you please change the font color in the comment box to black instead of light gray?)

  17. I am new to a no grain diet as well as no red meat or pork. Plus no processed sugars. I bake myself and use maple syrup but sometimes honey. In the past I ate a lot of unhealthy sweets but not bread.
    Occasionally in the past I have felt weak and shakey but eating did not help it. The only thing that did was something like a candy bar or other processed candy. Since starting this no grain diet but super high fats I still have this problem. However if I do not have access to processed sweets I am risking passing out. After eating a candy bar or two I feel great and go about my normal activities.
    I have no idea what any of this means or how to fix it.
    Any suggestions would be most appreciated.

    1. Now that monitoring how you feel has alerted you to the problem, you need data. Get a glucose monitor – low cost or even free with an online coupon – and test!

    2. Also, when was the last time you just drank a half cup of milk? I learned recently how important calcium is for my well being and I started doing that again. Really helps. Use fermented milk if you must, like yogurt.

  18. Just finished building a Finnish sauna for my wife and I. Pretty impressive how effective it is in lowering my blood pressure. My pressure used to hover around 125/72 it is now 115/55 HRV has also trended upwards. From what I have read on Dr. Rhonda Patrick’s blog and heard from her videos I can expect similar improvements in glucose/insulin. We have been using it for 2.5 weeks every morning for 30 minutes at 190f. From time to time I lift weights before entering.

    I am 63 years old and low carb.

  19. Love the article!
    Would love to learn more about hypoglycemia. I recently took a test and found out that my health issues is in low blood sugar. Any suggestions on a diet, meal frequency?

    Thanks in advance