Not telling your doctor
People have a variety of reasons for not telling their doctor the complete truth, but one of them should not be going on a ketogenic diet. Ketogenic diets may be promoted as a magical weight-loss or metabolic-health-improving diet, but the fact is that they only work for around half of the population. Ketogenic diets can boost LDL ("bad") cholesterol in certain persons. Going keto might also put you at risk for kidney stones, especially if you have a family history of them.
Going low carb might be risky if you have genetic changes that produce carnitine enzyme shortages, mitochondrial problems, or porphyria. Always consult a certified healthcare professional before making any dietary or lifestyle changes. With their assistance, you may be able to make changes to your ketogenic diet to ensure you're not making costly blunders.