ApoB
Also called Apolipoprotein B, apolipoprotein B-100, Apo B
ApoB (apolipoprotein B) is a protein that sits on the cholesterol-carrying particles linked to arterial plaque: low-density lipoprotein (LDL), very low-density lipoprotein (VLDL) and related particles. It is not found on HDL, the so-called good cholesterol. Each of those particles carries one ApoB molecule, so measuring ApoB gives a count of the particles rather than the amount of cholesterol inside them.
That one-to-one ratio is why some clinicians regard ApoB as a more accurate guide to cardiovascular risk than a standard lipid panel, which reports cholesterol mass. The difference matters most when LDL particles are smaller and denser than usual, so that a cholesterol figure understates how many particles there are. ApoB does not require fasting on its own. What ApoB adds to a cholesterol result, and how it is read, is covered in ApoB: The Cholesterol Number Most Panels Leave Out.
Why it matters after 45
Midlife is when cardiovascular risk usually gets a closer look, and it is also when the conditions in which a lipid panel is least reliable become more common. Cleveland Clinic notes that ApoB can be a better risk predictor for people with metabolic syndrome or diabetes, whose LDL particles may be smaller or denser, and type 2 diabetes becomes more common with age. ApoB is also sometimes measured after a statin is started, as another way to see where risk stands.
Where it comes up
Related terms
References
- Cleveland Clinic. Apolipoprotein B (ApoB) Test. https://my.clevelandclinic.org/health/diagnostics/24992-apolipoprotein-b-test
- Cleveland Clinic. Cardiac Blood Tests. https://my.clevelandclinic.org/health/diagnostics/22207-cardiac-blood-tests
- National Institute of Diabetes and Digestive and Kidney Diseases. Risk Factors for Type 2 Diabetes. https://www.niddk.nih.gov/health-information/diabetes/overview/risk-factors-type-2-diabetes
Definitions here are educational and are not medical advice. They explain what a term means; the pages linked above cover what it means for you, and a clinician reviews your own results. Editorial & medical review policy · All glossary terms