Skip to content

Apolipoprotein B (serum/plasma)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of apolipoprotein B, a protein found in low-density lipoproteins (LDL) and very low-density lipoproteins (VLDL) in your blood.

Quick summary

["Apolipoprotein B helps assess cholesterol and lipid metabolism."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
6685-2
Short code
Deprecated Apo B/Apo A-I SerPl-mRto
Synonyms
Deprecated Apo B/Apo A-I SerPl-mRto
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Is Apolipoprotein B Used For?

Apolipoprotein B is primarily used to evaluate your risk of heart disease and other cardiovascular conditions. It helps doctors assess cholesterol levels and identify potential issues with lipid metabolism, which can influence heart health.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is then sent to a lab for analysis. Apolipoprotein B is measured in the serum or plasma portion of the blood.

Why Might You Need This Test?

Your doctor may order this test if you have a family history of heart disease, high cholesterol, or other risk factors for cardiovascular problems. It may also be used to monitor treatment for conditions affecting lipid levels.

What Do Results Mean?

Higher than expected levels of apolipoprotein B may indicate an increased risk of heart disease, while lower levels might suggest other metabolic or genetic conditions. Your doctor will interpret results in the context of your overall health and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Apolipoprotein B plays a critical role in cholesterol transport and cardiovascular risk assessment. Elevated levels are often associated with higher LDL cholesterol, which can contribute to plaque buildup in arteries. It helps guide treatment decisions for managing cholesterol and reducing heart disease risk.

Short name

Apolipoprotein B

Frequently asked questions

Why do doctors sometimes order this test alongside cholesterol tests?
Doctors often use apolipoprotein B in combination with cholesterol tests because it provides a more precise measure of LDL particle number, which is closely linked to heart disease risk. While total cholesterol and LDL cholesterol are important, apolipoprotein B helps identify smaller, more dangerous LDL particles that can contribute to plaque formation.
What are common reasons for abnormal apolipoprotein B results?
Abnormal results may be due to genetic conditions affecting lipid metabolism, chronic kidney disease, diabetes, or certain medications. High levels can also occur in people with obesity or metabolic syndrome. Your doctor will investigate further if results are outside expected ranges.
How often should I get this test?
The frequency depends on your health status. If you have known cardiovascular risk factors, your doctor may recommend testing every few years or as needed to monitor changes in your lipid profile. Regular check-ups are the best way to determine your schedule.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy