What Is Apolipoprotein B? The Cholesterol Test Most People Don’t Know About

You probably know that high levels of low-density lipoprotein (LDL), or the “bad” cholesterol, can raise your risk for heart attack and stroke. But you may not have heard about apolipoprotein B (ApoB). 

The usual numbers in your cholesterol test (lipid profile) may leave out this important measure of your risk for heart disease. Scientists and lipid specialists have known about the harms of high ApoB for years, but it’s getting more attention now. For people who are at risk for heart disease, it may be an important number to know.

In this article, we look into ApoB, what causes its high levels, what you need to lower it, and how to test for it.

What is apolipoprotein B?

Apolipoprotein B (ApoB) is a protein found on the surface of certain particles in your blood. You can think of these particles as tiny packages that carry cholesterol and fat. This is an important process that helps deliver energy to your muscles and other organs. But problems can happen when there are too many ApoB-containing particles in the blood. 

ApoB is found on particles that can cause plaque to build up in your arteries. LDL cholesterol — the “bad” type of cholesterol — is one of these particles. Over time, plaque (atherosclerosis) can narrow your arteries and create blockages. These blockages are what cause heart attacks and strokes.

What do high apolipoprotein B levels mean?

A high ApoB level means there are a lot of harmful cholesterol-carrying particles in your blood. In general, having more particles means you are at greater risk for heart attack and stroke.

A target (or “good”) ApoB level depends on your risk for heart disease. In general, many experts aim for:

• ApoB below 100 mg/dL for people at moderate risk

• ApoB below 80 mg/dL for people at high risk

• ApoB below 65 mg/dL for people at very high risk 

A high ApoB level means something a little different from the usual measurement of LDL cholesterol. Your LDL cholesterol number tells you how much cholesterol is being carried inside the LDL particles. But it doesn’t tell you exactly how many particles are carrying that cholesterol. ApoB helps answer that question. It gives a better estimate of the total number of plaque-forming particles circulating in your blood.

What causes high apolipoprotein B levels?

Here are the main reasons that people have high ApoB levels:

• Genetics

• Insulin resistance, which is often linked to prediabetes, Type 2 diabetes, and metabolic syndrome

• High triglycerides

• A diet high in refined carbohydrates, added sugars, excess calories, and saturated fat

• Lack of regular exercise

• Having obesity

• Hypothyroidism (low levels of thyroid hormone)

• Kidney disease

• Steroids, including anabolic steroids

• Smoking

There are a few medications — including certain older beta blockers, some thiazide diuretics, and some older HIV medicines — that may affect ApoB levels in some individuals. If you’re taking one of these and your ApoB is high, check with your healthcare professional to see if there might be an alternative.

How do you lower apolipoprotein B?

Many of the same steps that lower LDL cholesterol can also lower ApoB. These include:

• Following a heart-healthy Mediterranean way of eating

• Limiting food high in saturated fats like butter, coconut oil, and fatty meats

• Doing regular exercise

• Maintaining a healthy body weight

• Limiting alcohol

The medications that lower LDL cholesterol also improve ApoB. These include:

• Statins (Crestor, Lipitor, Pravachol, and others)

• PCSK9 inhibitors (Repatha, Praluent, Leqvio, Lerochol)

• Bempedoic acid (Nexletol)

• Ezetimibe (Zetia), especially when combined with a statin

A few stronger specialty medications can also lower ApoB, including lomitapide (Juxtapid) and evinacumab (Evkeeza). These are usually used only for rare genetic cholesterol disorders, such as homozygous familial hypercholesterolemia. They aren’t used for most people with mildly or moderately high ApoB. 

It’s likely that in the future more medications that target ApoB will become available.

Who needs an apolipoprotein B test?

Not everyone needs an ApoB test. For many people, the usual cholesterol panel gives enough information to guide care. But ApoB levels can be especially useful for people who have:

• High triglycerides

• Type 2 diabetes, prediabetes, or metabolic syndrome

• Excess weight around the belly

• Fatty liver disease

• A family history of early heart disease

• Known heart disease, especially if LDL is well controlled

A healthcare professional can help you decide if an ApoB test might be useful for you. 

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Written by:

Sarah A. Samaan, MD

Sarah Samaan, MD, FACC, FACP, FASE is a board-certified cardiologist who practiced clinical cardiology for nearly 30 years. She is a member of the American College of Cardiology and the American College of Physicians, among others.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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