Should I ask for ApoB and Lp(a)?
Written and medically reviewed by Zahraa Sater, M.D., M.P.H.
Reviewed August 12, 2026 · Next review due August 12, 2028
Short answer
Lipoprotein(a) is worth measuring once in most adults, since the 2022 European Atherosclerosis Society consensus recommends testing at least once in adult life and the level is largely genetic. Apolipoprotein B is most useful when triglycerides are 200 mg/dL or higher or LDL looks deceptively normal; the 2018 AHA/ACC guideline treats ApoB of 130 mg/dL or above as a risk-enhancing factor.
Apolipoprotein B and lipoprotein(a) answer different questions, and conflating them is the reason people order both without knowing what to do with either. Apolipoprotein B counts how many atherogenic particles are circulating. Lipoprotein(a) identifies an inherited risk factor that a standard lipid panel cannot see. One is a refinement of a measurement you already have; the other is a one-off piece of family information.
What apolipoprotein B adds
Every LDL, VLDL and lipoprotein(a) particle carries exactly one apolipoprotein B molecule, so measuring ApoB counts particles rather than the cholesterol inside them. This matters when the two disagree. A person with insulin resistance often has many small cholesterol-poor LDL particles, which produces an ordinary LDL cholesterol with a high particle count. The 2018 AHA/ACC guideline states that an apolipoprotein B of 130 mg/dL or above corresponds to an LDL cholesterol of 160 mg/dL or above and constitutes a risk-enhancing factor, with a relative indication for measuring it when triglycerides are 200 mg/dL or higher.
What lipoprotein(a) adds
Lipoprotein(a) is set largely by genetics, changes little with diet or exercise, and is not reported on a standard lipid panel. The 2022 European Atherosclerosis Society consensus statement recommends measuring Lp(a) at least once in adults, with cascade testing of relatives in familial hypercholesterolaemia, a personal or family history of high Lp(a), and premature atherosclerotic cardiovascular disease. The 2018 AHA/ACC guideline names an Lp(a) of 50 mg/dL or 125 nmol/L or above as a risk-enhancing factor.
What actually changes with the result
A high Lp(a) does not currently have a drug that targets it in routine practice; therapies that lower Lp(a) directly are still being tested. What changes is the threshold for treating everything else. A high Lp(a) makes a borderline statin decision a clear one, raises the priority of blood pressure control and smoking cessation, and prompts screening of first-degree relatives. A high ApoB with an acceptable LDL means the LDL number was reassuring you incorrectly, and treatment intensity should follow the ApoB.
| Apolipoprotein B | Lipoprotein(a) | |
|---|---|---|
| What it measures | Number of atherogenic particles | An inherited lipoprotein not shown on a lipid panel |
| Threshold | 130 mg/dL or above is risk-enhancing | 50 mg/dL or 125 nmol/L or above is risk-enhancing |
| Changes with diet or statins | Yes, falls with lipid lowering therapy | Largely fixed |
| How often to test | To guide and monitor treatment | At least once in adult life |
A reasonable request: measure lipoprotein(a) once, and add apolipoprotein B if your triglycerides are 200 mg/dL or higher, if you have a strong family history, or if you are already on treatment and want to know whether the LDL number is telling the truth. Ask for the result in nmol/L, since the two units for Lp(a) are not interchangeable.
The clinical detail
Lp(a) assays differ in whether they report mass in mg/dL or particle concentration in nmol/L, and conversion between the two is not reliable because apolipoprotein(a) isoform size varies between individuals. Isoform-insensitive assays reporting nmol/L are preferred. Levels are largely genetically determined by the LPA gene and remain stable through adult life, which is why repeat measurement is generally unnecessary.
Apolipoprotein B is measured by standardised immunoassay, requires no fasting, and is not distorted by the calculation errors that affect Friedewald LDL at high triglycerides or at very low LDL levels. Where both are available, ApoB is the more reliable measure of atherogenic burden in patients with hypertriglyceridaemia, metabolic syndrome, diabetes or very low measured LDL cholesterol.
Written and medically reviewed by Zahraa Sater, M.D., M.P.H.
Reviewed August 12, 2026 · Next review due August 12, 2028
Sources
- 2018 AHA/ACC/Multisociety Guideline on the Management of Blood Cholesterol. American Heart Association and American College of Cardiology. DOI 10.1161/CIR.0000000000000625
- Lipoprotein(a) in atherosclerotic cardiovascular disease and aortic stenosis: a European Atherosclerosis Society consensus statement. European Atherosclerosis Society, European Heart Journal. DOI 10.1093/eurheartj/ehac361
- Cholesterol. MedlinePlus, National Library of Medicine
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