Apolipoprotein B, commonly known as ApoB, is the main protein found in low-density lipoproteins (LDL). Currently, LDL cholesterol is more frequently measured than ApoB levels because it’s included as part of a standard cholesterol test (lipid panel) for yearly physicals. And while ApoB is not included in standard cholesterol tests, emerging research indicates that ApoB is an essential indicator of heart health and heart disease risk. 
Here’s what you need to know about ApoB and how to get your ApoB levels tested.
What is apolipoprotein B?
Lipoproteins are round particles that transport fat and cholesterol throughout the body. Cholesterol must be transported throughout the body because it plays an essential role in producing many hormones throughout the body that are important for cellular health and function.
ApoB is a structural protein, found on all potentially atherogenic (or plaque-forming) particles.  So an ApoB blood test is a direct measure of the concentration of all atherogenic particles, including LDL cholesterol as well as other cholesterol markers like:
Very low-density lipoproteins (VLDL)
Intermediate-density lipoproteins (IDL)
These particles can either harmlessly pass through arteries (cholesterol clearance) or become trapped in the arterial wall. When ApoB and cholesterol particles are trapped in the arterial wall, the deposits can build up as plaque and restrict blood flow, damaging the arteries and increasing the chances of blood clots. [2,3]
Knowing your ApoB levels can help you and your healthcare provider further evaluate the status of your heart health and your potential risk for cardiovascular disease. 
What’s the reference range for an ApoB blood test?
Blood test results are often displayed against a reference range. Levels that fall outside of the reference range—say they’re too high or too low—should be addressed with your healthcare provider as they may indicate a health concern. Here’s what normal and high levels mean for an ApoB blood test.
Normal ApoB levels (40-120 mg/dL) can indicate healthy cholesterol transport and clearance. ApoB levels towards the higher end of this range may begin to indicate suboptimal cholesterol clearance.
High ApoB levels (greater than 120 mg/dL) can indicate decreased cholesterol clearance from the blood and an increased risk for cardiovascular disease. Consult with your physician if your ApoB levels are above 120 mg/dL.
Can ApoB levels be too low?
Yes, ApoB levels can be too low. Currently, 40-50 mg/dL is cited to be the lower end of the reference range.  However, further research is required to establish a standard consensus for the lower end of the reference range.
Low levels of ApoB likely result from medical conditions or diseases in the body including hyperthyroidism, cirrhosis, or malnutrition. While other blood tests are used to detect or diagnose those conditions, always seek proper medical attention and speak with a physician if you have concerns about low ApoB levels. [6-8]
What does a high ApoB mean?
Because ApoB-tagged particles carry LDL cholesterol throughout the body, elevated ApoB levels can indicate that the body cannot clear excess LDL cholesterol from the blood. With decreased clearance, more ApoB particles get deposited into the arterial walls. And when left unaddressed, elevated ApoB particles (mainly consisting of LDL cholesterol) can eventually increase plaque build-up, which narrows and constricts the arteries and increases the risk of heart disease. [3,4]
Studies show that high ApoB levels are associated with an increased risk for atherosclerosis (plaque build-up in the arteries), which, when left untreated, increases the risk of heart disease. And because heart disease is the leading cause of death in the United States, addressing ApoB and making cardioprotective lifestyle modifications is critical to living healthier longer. [2,3]
What do ApoB levels mean in relation to LDL cholesterol levels?
Knowing your ApoB level provides additional insights when interpreting other cholesterol markers like triglycerides, high-density lipoprotein (commonly called the “good” cholesterol), LDL, and total cholesterol. Because ApoB is found on all atherogenic particles, higher ApoB levels are often seen with elevated LDL cholesterol levels. That said, discordance between ApoB and LDL cholesterol levels is possible. In the cases of optimal ApoB levels yet high LDL cholesterol levels, or the reverse (elevated ApoB levels and optimal LDL cholesterol levels), consider referencing your ApoB levels for a more complete look at what’s actually going on with your heart health.  Here’s why.
ApoB is considered a more accurate measure of heart disease risk because it is a direct measure. While an LDL cholesterol blood test is a calculation (based on total cholesterol, HDL cholesterol, and triglycerides), ApoB is a direct measure. Every potentially atherogenic particle carries one ApoB, so you’re getting a direct count of all the particles that could contribute to cardiovascular disease in your bloodstream. 
How can you lower ApoB levels?
Like other cholesterol markers, ApoB levels are modifiable by lifestyle habits—meaning, nutrition, lifestyle, and supplement modifications can help improve high levels.
Here are a few of the most common science-backed ways to improve elevated ApoB levels.
Reduce foods high in saturated fat: Eating foods high in saturated fat is associated with elevated ApoB levels. Aim to reduce intake of red and processed meats to support ApoB levels. 
Opt for sources of unsaturated fats: Unsaturated fats, also known as “healthy fats” support optimal cholesterol and ApoB levels. Aim to incorporate unsaturated fats like olive oil, avocados, and flaxseed to support ApoB levels. [12-14]
Eat fiber-rich foods: Fiber is an important nutrient that contributes to optimal cholesterol levels and is critical in supporting ApoB levels. Oats and beans are two excellent food sources of soluble fiber—and research suggests that regular consumption of these foods is effective at lowering ApoB levels. [15,16]
Try out a new supplement: Certain supplements can also benefit your ApoB levels. Studies show that taking a psyllium husk or plant sterol supplement can reduce elevated ApoB levels. Other supplements like artichoke extract and spirulina are also studied for their impact on ApoB. [17,18] Always consult with a healthcare professional before adding a new supplement to your routine.
How long does it take ApoB levels to change?
The time it typically takes to see movement in your ApoB level will depend on multiple factors such as where your level currently is, your lifestyle habits, your willingness to adopt new habits, and your ability to stick to the habits you’ve formed. That said, the studies show that ApoB levels can be notably modified after approximately three months. [13,18,19]
How can you get your ApoB levels measured?
ApoB is currently not measured as part of standard cholesterol blood tests and many insurance companies don’t cover the test—especially for preventative screening. Depending on your healthcare provider, where you live, current cardiovascular risk factors, and your insurance, you may be able to get an ApoB test through your primary care provider.
Since ApoB is a critical marker of health, a cardiovascular indicator, and can be impacted through lifestyle choices, InsideTracker has added this biomarker to the Ultimate Plan. [2,4] InsideTracker’s science team has collected research on ApoB for over a year, and can now confidently say that the addition of this marker provides more context to other lipid markers and allows for a more comprehensive analysis of your heart health. The team established an optimal zone for ApoB levels within the reference range. Biomarkers that fall within a reference range don’t necessarily indicate optimal health, and according to the research, optimal heart health status is linked to ApoB levels less than 90 mg/dL.
If your levels are above optimal, you’ll also get science-backed recommendations to improve ApoB levels, which in turn support LDL cholesterol levels.
One last note about ApoB
ApoB is the main structural protein found in low-density lipoproteins (LDL) and all potentially atherogenic lipoproteins, and it assists in transporting and clearing cholesterol from the blood.
ApoB is a direct measure of atherogenic particles, making it an essential indicator of heart health.
High ApoB levels indicate decreased clearance of cholesterol from the blood.
ApoB is modifiable, meaning dietary changes and supplement intake can help to modify your ApoB levels.
Michelle Darian, MS, MPH, RDMichelle is a Nutrition Specialist at InsideTracker. As a Registered Dietitian, you’ll find Michelle analyzing the research behind recent nutrition trends, bringing actionable food and supplement recommendations to the platform. When she's not myth-busting, Michelle can be found exploring new restaurants and getting creative in her kitchen.