My ldl cholesterol was 5.2 mmol/l (upper bound was 5.2 mmol/l as well). yet i actually have a very low body fat. should i worry about this at all?

HDL?: All laboratory results need to be interpreted in the clinical context and the doctor who ordered the tests is usually in the best position to do that. Having said that, your LDL is higher than desired, but if your HDL is also high that may protect you. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, low fat milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.

Depends: all depends on ur family history and other risk factors; your body fat percentage has little to do with actual cholesterol levels; also ur risk would depend on HDL levels and other underlying medical history; in general upper limits of normal may followed clinically with repeat test in 3-6 months unless other factors point to the need for early intervention.