False-High and False-Low Cholesterol Tests

Medically reviewed by Anthony Pearson, MD, FACC

Cholesterol blood tests ordered by your healthcare provider are usually reliable, but it's possible to get a false-low or false-high cholesterol test result. In other cases, you may get a result that seems off, but is actually correct and due to a factor you may not have thought of, like a medication you are on.

There are several things that can affect your cholesterol test results, from alcohol consumption to pregnancy to simple human error. Knowing about these factors may prompt you to share important information with your provider that can help them better interpret your results.

This article goes over what can cause cholesterol test results to be inaccurate. It also reviews circumstances that can increase cholesterol levels, which your healthcare provider will take under consideration when evaluating your numbers.

What Cholesterol Tests Measure

A standard cholesterol test is also called a blood lipid test. For the test, a sample of blood is drawn and then analyzed in a lab to measure:

• Low-density lipoprotein (LDL) or “bad” cholesterol should be less than 100 milligrams per deciliter (mg/dL)

• High-density lipoprotein (HDL) or “good” cholesterol should be greater than or equal to 60 mg/dL

• Triglycerides (a type of fat blood the body uses for energy) should be less than 150 mg/dL

• Total cholesterol (the total amount of cholesterol in the blood based on your HDL, LDL, and triglycerides numbers) should be less than 200 mg/dL

Do Cholesterol Tests Require Fasting?

Research has shown that HDL/LDL cholesterol and triglyceride levels are generally not affected by food consumption the day before the test. In fact, nonfasting cholesterol tests have been shown to be more accurate than the traditional method, especially for measuring LDL (bad) cholesterol.

It's not always necessary to fast the night before you have a cholesterol test or get up early to have your blood drawn first thing in the morning before breakfast.

Ask your healthcare provider if a non-fasting cholesterol test might be an option for you.

Related:An Examination of the Cholesterol Hypothesis

Reasons For Inaccurate Cholesterol Test Results

Cholesterol tests are helpful, but they are not perfect. And sometimes, results are simply wrong. Here are a few reasons why that can occur.

Human Error

It's not common, but errors and reporting mistakes do happen. For example, there might have been a problem with how your blood sample was taken or how the sample was stored.

One way that you can help prevent an error is to make sure that the person who draws your blood asks for your identification and labels the tubes with the correctly-spelled information.

Lab Equipment Problems

The equipment labs use to test your blood sample is very powerful, but they can still "act up" like any machine.

If equipment is old, out of date, or hasn't been maintained, it's possible that it could produce some inaccurate results.

Mix-Ups

Medical professionals take steps to prevent patient sample mixups, but they can happen.

For example, if you got your blood taken for your cholesterol test and the lab was very busy that day, it's possible that your sample was labeled wrong. Your sample could even have gotten confused with someone else's.

If your results seem very off-base, it will be a "red flag" for your provider to follow up. If they don't find a medical explanation for the unexpectedly high levels, they can have you do the test again to see if the results are replicated. If not, a lab error is likely to blame.

Why High-Cholesterol Levels May Actually Be Accurate

Sometimes a too-high cholesterol result truly is reflective of your levels. Your cholesterol could be temporarily elevated due to a modifiable factor like exercise. Or it may now be chronically elevated due to something like a health condition.

Don't assume that surprising cholesterol results are inaccurate. Share your full medical history with your healthcare provider so they can consider the following possibilities, too.

Certain Medications

You might be taking medications that can affect your cholesterol levels. For example, corticosteroids and HIV medications can raise lipid levels.

Oral contraceptives (birth control pills) are a common medication that can make your cholesterol increase, though usually just a little.

If you're taking birth control only to prevent pregnancy, you might be able to switch to a different medication or try a different form of birth control (like an IUD) that may not affect your cholesterol. However, if you take birth control pills to manage a condition like polycystic ovary syndrome (PCOS) or premenstrual dysphoric disorder (PMDD)—and the medication is working well for you—switching or stopping it may not be an option.

While cholesterol is a contributor to your cardiovascular disease risk, it's not the only one. Factors like your diet and family history matter, too.

Your provider will consider your overall risk for cardiovascular disease when deciding if you should stop taking a medication that could be contributing to higher cholesterol levels. They will talk to you about the risks and benefits of continuing to take the medication against the risks and benefits of stopping it.

Learn More:Drugs That Increase Cholesterol

Pregnancy

Your cholesterol might be higher than usual while you're pregnant and even for a few months after you give birth. A cholesterol test should not be considered reliable until about four months postpartum.

Alcohol Consumption

Even occasional heavy drinking can negatively affect your cholesterol scores. Most experts advise that you avoid alcohol for 24 hours before your test.

Inflammation or Infection

Having inflammation or infection can affect your cholesterol numbers, particularly if these conditions are chronic.

Autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, and psoriasis may affect cholesterol scores.

Being Underweight

While overweight and obesity are known to contribute to high cholesterol levels, being on the other end of the weight spectrum can also affect your results.

Research has shown that people who are severely underweight from cancer or eating disorders like anorexia nervosa may have changes in their lab tests, including high cholesterol. The levels tend to get better and even go back to normal if a person gains weight.

While it's important for everyone to maintain healthy cholesterol levels, it's not clear whether having high cholesterol from being very underweight carries the same cardiovascular risks as having high cholesterol for another reason.

However, having high cholesterol for a long time for any reason may still contribute to a person's risk for cardiovascular disease.

Exercising

Regular physical activity can have a positive effect on your cholesterol levels in the long term, but avoid doing a hard workout right before you have your test.

Studies have shown that an intense workout 12 to 24 hours before your test might actually raise your cholesterol.

Genetics

If you're in otherwise great health, exercise regularly, eat well, and manage your stress, you'd be understandably caught off guard by a high cholesterol test result.

Research has shown that some people have genes that make them more likely to have higher "bad" cholesterol levels and/or lower "good" cholesterol levels (genetic predisposition).

There is also a genetic disorder called familial hypercholesterolemia that causes high cholesterol levels to run in families—but many people don't know they have it. A higher-than-expected cholesterol test could be a clue that you have the condition, especially if other members of your family have high cholesterol or heart disease.

Finding out and taking steps to manage your levels is very important because having familial hypercholesterolemia raises your risk of getting heart disease at an early age.

If you think your cholesterol results are not accurate, talk to your healthcare provider. Don't hesitate to ask for a repeat test. If any factors that could have influenced your results may have been at play, be sure to mention them if you haven't already.

Summary

Cholesterol tests can be an important marker of your health, but they aren’t perfect. Certain health conditions and medications, as well as factors related to when you had the test done, can lead to inaccurate results.

If you think your cholesterol test results seem wrong, talk to your provider. They might want to do the test again to re-check and make sure that the numbers are accurate. They may also want to take certain factors (like medications you take) into account when they interrupt your test results.