One on one with your ducks in a row. Quietly lay out the facts as you've researched them. If it's someone you love, end with something like, "I love you, so I wanted you to know this. I won't be offended if you take your doctor's advice over mine, but please be aware that doctors are oriented to fix symptoms, not cure causes." Or something like that. No matter what the person chooses, you'll know you've done your best.