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Should I Fast Before I Have My Cholesterol Test?

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Updated May 21, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Should I Fast Before I Have My Cholesterol Test?

Copyright: Monkey Business Images, istockphoto

Copyright: Monkey Business Images, istockphoto
Question: Should I Fast Before I Have My Cholesterol Test?
Answer:

Before you have any type of blood test at your healthcare provider’s office -- including a lipid profile -- you're usually told that you need to fast before taking the test. Current recommendations suggest that you refrain from eating anywhere between 8 and 12 hours before having your blood drawn for the cholesterol test. But this can prove to be problematic, especially if you have an afternoon appointment or if the hunger pangs are just too unbearable for you to wait to eat until after you take your test. Some studies suggest that you may not need to fast before having your cholesterol checked.

To Fast or Not to Fast before Your Cholesterol Test?

Only a handful of studies have examined the effect that fasting has on blood lipids, which include high-density lipoprotein (HDL), low-density lipoprotein (LDL) and triglycerides. These studies involved analyzing blood levels of these lipids, which were taken anywhere between one and 16 hours after eating. The results indicated that fasting does not appear to have a significant impact on some aspects of your lipid profile; for instance, some lipids such as HDL only had about a 2% variation between fasting and non-fasting individuals tested. On the other hand, triglyceride levels appear to have up to a 20% variation between fasting and non-fasting participants. LDL cholesterol, which can either be measured directly or calculated using HDL and triglyceride levels, appeared to have up to a 10% variation between those who ate before their test and those who fasted. Apolipoproteins measured in some of these studies did not appear to be affected by whether or not food was consumed before the cholesterol test.

In other words, while your HDL levels may vary slightly depending upon whether or not you ate before your test, your LDL and triglyceride levels do vary a little bit more and could affect your results.

The studies also didn’t account for food consumed before the cholesterol test. Some foods, such as those high in sugar and saturated fat, could cause triglyceride levels to increase.

Bottom Line

The variation in HDL, LDL and triglycerides appears to be small in some cases, which may offer hope for those of you who have trouble refraining from food before your cholesterol test. But in some cases, it may be a good idea to refrain from eating before your cholesterol test — especially if you're trying to get your lipids into a healthy range or would like accurate triglyceride level results.

If you're concerned about whether or not you should fast before getting your cholesterol checked, always check with your healthcare provider first before you attend your appointment. While some lipids in these studies did not appear to be greatly affected by eating before the test, other lipids did appear to have some variation depending upon whether or not food was consumed before the test. Additionally, your healthcare provider may want to conduct other blood tests during your visit, such as a blood glucose test, that could be sensitive to whether or not you've eaten.

Sources:

Sidhu D, Naugler C. Fasting time and lipid levels in a community-based population. Arch Intern Med 2012;E1-E4.

Di Angellantonio E, Sarwar N, Kaptoge S, et al. Major lipids, apolipoproteins, and the risk of vascular disease. J Am Med Asso 2009;302:1993-2000.

Branchi A, Torri A, Berra C, et al. Changes in serum triglycerides and high density lipoprotein concentrations and composition after a low-fat mixed meal: effects on gender and insulin resistance. Intern Emerg Med 2006;1:287-295.

Gazanio JM. Should we fast before we measure our lipids? Arch Intern Med 2012;E1-E2.

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