Harvard Heart Letter

Fasting before a cholesterol test

Ask the doctor

cholesterol test LDL
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Q. Do I still need to fast before getting a cholesterol test? I heard that doing so may not be necessary.

A. For decades, we've told people not to eat or drink (except for water) for eight to 12 hours before a cholesterol test. This was based on the belief that fasting provides a more accurate assessment of all the lipids (fats) in the blood, which include cholesterol and triglycerides, a type of fat-carrying particle. But recent studies show that the differences between fasting and nonfasting values for cholesterol are usually negligible.

In addition, many large, long-term studies suggest that nonfasting lipid values are just as good (and perhaps even better) for predicting a person's risk of cardiovascular disease. That may reflect the fact that we aren't in a fasting state for most of the day. So a nonfasting measurement likely gives a clearer picture of our usual lipid levels.

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