Why Vigorous Exercise Before a Cholesterol Test Can Mess With Your Results

Working out can temporarily raise your cholesterol levels. It sounds counterintuitive, but engaging in intense exercise right before a cholesterol test may mess with the results, making your low-density lipoprotein (LDL or "bad") cholesterol appear higher than it actually is.

If you're scheduled for a lipid panel, your doctor may recommend avoiding super high-intensity workouts for a day or so to ensure the results are as accurate as possible, says Dennis Bruemmer, MD, PhD, a cardiologist and director of the Cleveland Clinic's Center for Cardiometabolic Health, in Cleveland, Ohio.

"We generally recommend to not engage in intense aerobic exercise prior to lipid testing," Dr. Bruemmer explains. "Any extreme changes in routine lifestyle prior to testing may affect lipid test results, [and] this includes an increase in LDL after intense exercise."

However, this shouldn't be a reason to avoid exercising. As Dr. Bruemmer says, healthy physical activity, paired with a diet low in saturated fats, can lower bad cholesterol by up to 10 percent in the long-term. And according to the American Heart Association (AHA), just 150 minutes of moderate-intensity aerobic exercise each week can help lower your cholesterol levels.

In other words, exercise in general is great for your cholesterol levels — just not when it's right before your blood test.

LDL is the type of cholesterol doctors often caution you to watch out for. Too much of it can lead to a buildup of plaque on the walls of your arteries, increasing your risk for heart attack and stroke over time, according to the AHA. This condition is called atherosclerosis, and it can become quite dangerous for your heart health if left unchecked.

However, cholesterol medications along with diet and lifestyle modifications can help bring dangerous LDL levels into a healthy range. For this reason, the AHA recommends all adults older than 20 have their cholesterol levels tested every four to six years, and that people who are already at an elevated risk for heart disease talk to their doctor about getting the tests done more often.

A 12-hour fast — meaning avoiding all food and drink except water — before getting your blood drawn will assure the most accurate LDL reading, according to the Cleveland Clinic.

While pre-test fasting has been the general recommendation from doctors for years, recent research has shown it might not be necessary for all types of cholesterol tests, according to Harvard Health Publishing.

Unless you arrive at your test having just eaten a super-high-fat meal, scientists now recognize that eating tends to affect your results very minimally, and for a lot of people, the inconvenience of fasting can be a reason to avoid getting the test in the first place. In other words, according to Harvard Health Publishing, experts are now realizing it's better to get tested and see a slight increase in your levels than to not get tested at all.

That being said, whether you'll need to fast before your lipid profile is up to your doctor, so it's best to follow their recommendations.