High cholesterol is a major risk factor for heart attack, stroke and cardiovascular disease, according to the U.S. National Library of Medicine. An accurate cholesterol blood test, also called a lipid panel, is important for assessing your risk level for these conditions.
Certain medications, critical illness and possibly eating too soon before a cholesterol blood test can affect cholesterol readings, Robert Eckel, MD, professor of medicine, emeritus, at the University of Colorado, Anschutz Medical Campus, former president of the American Heart Association and president of the American Diabetes Association, tells LIVESTRONG.com. But, he adds, "There's no such thing as a false high cholesterol test." A high test result still means a person has high cholesterol.
Find out more about the causes of high cholesterol.
1. Food and Cholesterol Levels
Cholesterol is a waxy, fat-like substance produced in the liver, according to the American Heart Association. Though you may think of cholesterol as "bad," the body actually needs cholesterol to function properly.
Cholesterol can also be found in foods such as meat, dairy, eggs and baked goods. However, the relationship between food and blood cholesterol is more complicated than previously believed.
Until recently, it was though that eating lots of cholesterol-rich foods played a significant role in causing high blood cholesterol. But a major 2015 report by the USDA Dietary Guidelines Advisory Committee found that cholesterol from food — called dietary cholesterol — has a much smaller effect on a person's blood cholesterol.
Instead, a diet high in fats (particularly saturated fats) and carbohydrates has a much greater effect on blood cholesterol, according to the Harvard T. H. Chan School of Public Health. But you should note that many cholesterol-rich foods are also high in saturated fats. This is why Dr. Eckel says it's still best to limit or avoid meat, dairy and baked goods.
Eating fatty foods can temporarily raise cholesterol levels, Dr. Eckel says. Because of this, patients are often required to fast before a lipid panel. However, Dr. Eckel notes fasting before a cholesterol test may no longer be necessary. A study published May 2018 in the Journal of the American Medical Association (JAMA) compared fasting and non-fasting lipid panel results and found that the difference in LDL cholesterol levels (so-called "bad" cholesterol) was not scientifically meaningful.
In short: Contrary to previous thought, dietary cholesterol isn't a significant risk factor for high cholesterol and eating before a test is not likely to cause a false reading. However, Harvard Health Publishing notes that eating can lead to an increase in triglyceride levels, which are also often checked in a lipid panel. So, while non-fasting lipid panels are generally recommended, there are exceptions — when in doubt, check with your healthcare provider before your lipid panel to see if you need to fast.
Certain medications, such as estrogen-replacement therapy (used by menopausal women to manage their symptoms), can cause higher cholesterol levels, according to the Cleveland Clinic. But estrogen therapy causes higher levels of HDL ("good" cholesterol), not LDL. Your doctor will be able to see from the tests whether elevated cholesterol is caused by HDL or LDL. If it is caused by HDL, there's generally no cause for concern.
Dr. Eckel adds that steroid medications can "modify cholesterol levels in a major way." Be sure to discuss all your medications with your doctor before your test.
Additionally, critical illnesses like kidney disease can also affect blood cholesterol, according to the National Kidney Foundation.
Read more: The Normal Cholesterol Range for Men
What About Home Cholesterol Tests?
You don't have to see your doctor to check your cholesterol; you can also check your cholesterol at home. These home cholesterol test kits can usually be purchased at your local pharmacy. But not all home test kits are the same, according to the Mayo Clinic.
There are a number of different cholesterol test kit brands and therefore different levels of accuracy. Per the Mayo Clinic, the most accurate tests are ones affiliated with the U.S. Centers for Disease Control and Prevention (CDC) programs. These test meet the rigorous standards of the CDC.
However, the Mayo Clinic notes that most home cholesterol kits only measure total cholesterol levels. As mentioned, if a high cholesterol test is specifically caused by high levels of HDL (which many at-home tests don't measure), it's unlikely a person is at risk for heart disease. Be sure to discuss your home cholesterol test results with your doctor.
Is This an Emergency?
- U.S. National Library of Medicine: "Cholesterol Levels"
- American Heart Association: "Control Your Cholesterol"
- USDA: "Scientific Report of the 2015 Dietary Guidelines Advisory Committee"
- Harvard T. H. Chan School of Public Health: "Cholesterol"
- Journal of the American Medical Association: "Association of Nonfasting vs. Fasting Lipid Levels With Risk of Major Coronary Events in the Anglo-Scandinavian Cardiac Outcomes Trial–Lipid Lowering Arm"
- Cleveland Clinic: "Estrogen & Hormones"
- National Kidney Foundation: "High Cholesterol = High Kidney Disease Risk"
- Mayo Clinic: "Cholesterol Test Kits: Are They Accurate?"
- Harvard Health Publishing: "Farewell to the Fasting Cholesterol Test?"