New guidelines simplify cholesterol tests: no fasting needed

I’m supposed to have my cholesterol checked soon. It’s a simple test, but I’m not looking forward to it since it requires fasting overnight. And that means making a special early-morning trip to my doctor’s office.

But new international guidelines say it’s OK — even preferred — to skip the overnight fast.

To learn more about this small but oh-so-useful shift, I talked with cardiologist Dr. Samia Mora. She helped write the new guidelines, which were published this week in the European Heart Journal and summarized in JAMA Internal Medicine. Mora is director of the Center for Lipid Metabolomics at Brigham and Women’s Hospital and associate professor of medicine at Harvard Medical School.

What was the point of fasting before having a cholesterol test?

Not eating for eight to 12 hours before having blood drawn for a cholesterol test was thought to give a more accurate assessment of total cholesterol, harmful LDL cholesterol, protective HDL cholesterol, and triglycerides, a type of fat-carrying particle. We now know better.

One problem with fasting is that we spend most of the day in the nonfasting state, so the way cholesterol tests are currently done doesn’t necessarily give a clear picture of “normal” levels. Another is that fasting is a hassle for everyone concerned — patients, clinicians, and even lab workers.

What’s behind the new recommendation?

This change has been coming for some time. It is driven by data from a dozen-plus studies that include more than 300,000 people whose cholesterol and other lipids were measured when they hadn’t fasted. Their levels predicted cardiovascular risk, as well as, or possibly better than, fasting lipid levels.

Nonfasting levels might be better?

After you eat, your digestive system converts some of the carbohydrates and fats into triglycerides. Their level in the bloodstream rises, then gradually falls. If the triglyceride level rises too much, it’s a signal that the body has trouble metabolizing food. Think of eating as a stress test for metabolism. That’s something you can’t see if you’ve been fasting.

What does this shift mean?

Everyone wins with this change. People don’t like to fast overnight. Some find it difficult to do, others are even harmed by it, such as those who faint from fasting and people with diabetes who take medications to lower blood sugar. The new recommendation means you can have your blood drawn when it’s most convenient for you, rather than early in the day.

It may even mean one-stop shopping — you can have your blood drawn and then see your doctor, all in the same visit. It’s easier for clinicians, who don’t have to keep track of patients’ special lab visits. Eliminating the fasting requirement will benefit labs, too, since they won’t have to deal with the daily crush of patients first thing in the morning needing blood draws for cholesterol checks.

Does what you eat before the test matter?

Consuming a double cheeseburger, fries, and a milk shake right before having your blood drawn for a cholesterol test may lead to a follow-up fasting test if the triglycerides are very high. But eating normally has little effect on your lipid levels, including triglycerides.

Will this recommendation catch on in the United States?

Health care providers often do what they are used to doing, so it may take a while for some to change to nonfasting cholesterol tests. But we also need to realize that there are advantages to this evidence-based change. Switching to nonfasting cholesterol testing is actually the path of least resistance for patients and clinicians. It also provides a more accurate lipid profile for individual patients.

I believe that getting the word out to clinicians, lab directors, and patients will be enough to make the switch to nonfasting cholesterol tests in a fairly short time.