Why is my cholesterol high if I eat well and exercise?

Genes set most of your LDL level. Food and exercise usually move it by 10 to 30%.

Your liver makes most of the cholesterol in your blood, and how well it clears LDL is largely inherited. About 1 in 250 people has familial hypercholesterolemia (FH), a genetic cause of very high LDL from birth.

Other things can raise LDL too: an underactive thyroid, some kidney and liver conditions, menopause, and some medicines. A simple blood test can check your thyroid.

Source: European Atherosclerosis Society FH consensus, Eur Heart J 2013; 2018 AHA/ACC cholesterol guideline.