Also Known As
Apolipoprotein B-100
Apolipoprotein B-48
Formal Name
Apolipoprotein B
This article was last reviewed on
This article waslast modified on
21 May 2018.
At a Glance
Why Get Tested?

To help evaluate your risk of developing cardiovascular disease (CVD) and to diagnose people with specific Apo B disorders.

When To Get Tested?

This is a non-standard test currently limited mostly to hospital specialists. It can be measured when you have a personal or family history of heart disease and/or high concentrations of lipids in the blood (hyperlipidaemia) and your doctor is trying to determine your risk of developing CVD; sometimes measured to help monitor treatment for hyperlipidaemia or to help diagnose a rare apo B deficiency

Sample Required?

A blood sample taken from a vein in your arm

Test Preparation Needed?

None; however, this test is often requested at the same time as other tests that require fasting (water only), so you may be instructed to fast for 12 hours prior to having this test.

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you will be able to access your results online.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, gender, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

This test measures the amount of apolipoprotein B (apo B) in the blood. Apolipoproteins are the protein component of lipoproteins, complexes that transport lipids throughout the bloodstream. Apolipoproteins provide structural support to lipoproteins and shield the water-repellent (hydrophobic) lipids at their centre.

There are two forms of apolipoprotein B: apo B-100 and apo B-48. Apo B-100 is made by the liver, while apo B-48 is produced in the intestines. Apo B-48 is an integral part of the structure of chylomicrons, large lipoproteins responsible for the initial transport of dietary lipids from the intestines to the liver. In the liver, the body repackages the lipids and combines them with apo B-100 to form triglyceride-rich very low density lipoprotein (VLDL). In the bloodstream, an enzyme called lipoprotein lipase (LPL) removes triglycerides from VLDL to create first, intermediate density lipoproteins (IDL) and then, low density lipoproteins (LDL - the "bad" cholesterol). Apo B-100 is recognised by receptors on the surface of many of the body's cells which promote the uptake of cholesterol into the cells.

The cholesterol that LDL and apo B-100 transport is a vital component of the membranes surrounding cells and for the production of several hormones. In excess, however, LDL can lead to the formation of fatty deposits (plaques) in artery walls and the hardening and scarring of blood vessels. These fatty deposits narrow the vessels in a process termed atherosclerosis which increases the risk of heart disease and a heart attack. The LDL cholesterol (LDL-C) test is routinely requested as part of a lipid profile. The value is frequently calculated by laboratories using the concentrations of total cholesterol, high density lipoprotein cholesterol (HDL-C) and triglyceride. The calculation becomes less reliable as the triglyceride concentration rises. Rarely laboratories will directly measure LDL-C concentration.

Laboratory tests for apo B typically measure only apo B-100 but are often reported as simply apo B. Apo B-100 concentrations tend to mirror the concentration of LDL-C. Many experts think that in the future, the concentration of apo B may eventually prove to be a better indicator of risk of cardiovascular disease (CVD) than LDL-C. However, the clinical use of apo B and that of other emerging cardiac risk markers such as apo A-I, Lp(a), and hs-CRP is not fully established.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No special preparation is needed for an apolipoprotein B test. However, this test is often requested at the same time as other tests that do require fasting (water only), such as LDL-C, HDL-C and triglycerides. Therefore, you may be instructed to fast for 12 hours prior to having this test.

Accordion Title
Common Questions
  • How is it used?

    Apo B concentrations may be used alongside the results of other lipid tests, to help determine an individual's risk of developing cardiovascular disease (CVD). The test is not used as a general population screen but may be requested if a person has a family history of heart disease and/or high concentrations of lipids in the blood (hyperlipidaemia). It may be performed, with other tests, to help diagnose the cause of hyperlipidaemia, especially when someone has elevated triglyceride concentrations, which can prevent the accurate calculation of LDL cholesterol.

    A doctor may request both an apo A-I test (associated with high-density lipoprotein (HDL), the "good" cholesterol) and an apo B test to determine an apo B/apo A-I ratio to evaluate risk for developing CVD.

    Apo B concentrations may be used to monitor the effectiveness of lipid treatment as an alternative to non-HDL-C (non-HDL-C is the total cholesterol concentration minus the amount of HDL-C). In rare cases, an apo B test may be requested to help diagnose a genetic problem that causes over- or under-production of apo B.

  • When is it requested?

    Apo B may be measured with  apo A-I or other lipids, when a doctor is trying to evaluate someone's risk of developing CVD and when a person has a personal or family history of heart disease and/or hyperlipidaemia, especially when they have a significantly elevated triglyceride concentration. Sometimes apo B is requested to monitor a person who is undergoing treatment for hyperlipidaemia. Rare disorders of apo B can present at any age, including in new born babies and cause many problems including vitamin deficiencies and neurological abnormalities.

  • What does the test result mean?

    Elevated concentrations of apo B correspond to elevated concentrations of LDL-C and to non-HDL-C and are associated with an increased risk of CVD. Elevations may be due to a high fat diet and/or decreased clearance of LDL from the blood.

    Some genetic disorders are the direct (primary) cause of abnormal concentrations of apo B. For example, familial combined hyperlipidaemia is an inherited disorder causing increased concentrations of cholesterol and triglyceride in the blood. Abetalipoproteinemia, also called Apolipoprotein B deficiency or Bassen-Kornzweig Syndrome, is a very rare genetic condition that can cause abnormally low concentrations of apo B. For more on some of these disorders, see the MedlinePlus Medical Encyclopedia web page: High blood cholesterol and triglycerides.

    Abnormal concentrations of apo B can also be caused by underlying conditions or other factors (secondary causes). Increased concentrations of apo B are seen, for example, in:

    Apo B concentrations may be decreased in any condition that affects lipoprotein production or affects its synthesis and packaging in the liver. Lower concentrations are seen with secondary causes such as:

    An increased ratio of apo B to apo A-I may indicate a higher risk of developing cardiovascular disease.

  • Is there anything else I should know?

    Some elevations of apo B-100 (and LDL-C) are due to mutations in the apo B gene that cause it to produce apo B-100 that is not recognised as easily by LDL receptors. Other mutations are in the LDL receptor system of the liver cell that recognises apo B-100. These genetic defects impede the clearing of LDL from the blood and result in its accumulation in the circulation, increasing the risk of heart disease. The apo B test is not routinely used for CVD risk assessment and does not replace the lipid tests commonly available.

  • Should my doctor be measuring apo B-48?

    While researchers are looking into the role of chylomicrons (the lipoprotein that contains apo B-48), there is currently no reason to measure apo B-48.

  • What can I do to lower my apo B?

    Diet and exercise changes that lower LDL concentrations (and increase HDL, the good cholesterol) will lower your apo B concentrations and decrease your risk of heart disease.