Fasting Before a Cholesterol Test: Do You Really Have To?

New thinking has changed the standard recommendations.

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Nobody likes having to fast before a health screening. Even if you’re not a regular breakfast eater, there’s something about being forbidden to grab a bite before heading to the doctor’s office that really gets in your head. Suddenly every billboard advertising cheap coffee and drive-thru egg sandwiches is calling your name, #amiright?

For years, doctors required eight to 12 hours of fasting before testing cholesterol panels. (Learn more about what cholesterol is here.) The thinking was that testing in a fasting state would allow a more accurate and reliable reading due to food’s effect on lipid levels.

But that thinking has changed.

A 2016 study by researchers at Harvard Medical School revealed that cholesterol levels did not vary significantly between fasting and nonfasting states. “The only part of the cholesterol panel that is affected is the triglycerides,” says Rachel Bond, MD, a cardiologist at Lenox Hill Hospital. According to the study, triglyceride levels varied up to 25 mg/dL between fasting and nonfasting states. (Here’s how to interpret cholesterol numbers.)

“If you’ve had a fatty meal close to the time of the blood draw, your triglyceride level can be elevated,” says Paul Knoepflmacher, MD, a clinical instructor in medicine at The Mount Sinai Hospital.

Some studies even suggest that measuring after a meal may even be advantageous, since a non-fasting state is a better representative of how your body usually exists. For that reason, lipid levels after eating might better predict the risk of heart disease.

These new findings have changed fasting recommendations for routine cholesterol checks. The stance is now that fasting is “preferred” but not mandatory. If you don’t mind fasting, going to your appointment hungry is one way to ensure you won’t have to make a trip back.

One notable exception: If you have a personal or family history of high triglycerides, your doctor may ask you to fast, according to Dr. Bond. “If you don’t know,” cautions Dr. Bond, “to make it easier for you, your doctor may suggest you fast just so you don’t have to come back and get [your blood] checked again.”