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Apolipoprotein A1 (ApoA1)

The main protein in HDL particles. Higher levels usually go along with higher HDL cholesterol and are linked to a lower chance of heart disease.

AI-verified against cited sources. Awaiting expert reviewAlso called ApoA1, Apo A-I, ApoA-ILOINC 1869-7

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What it is

Apolipoprotein A1 (ApoA1) is the main protein on HDL, the particles that carry extra cholesterol out of your tissues and back to the liver. Each HDL particle usually carries two to five ApoA1 molecules, so the test gives a rough idea of how much HDL you have. HDL cholesterol, by comparison, measures how much cholesterol is inside those particles. ApoA1 is not part of a routine lipid panel. It is often ordered with ApoB, and you generally do not need to fast for it.

Why it matters

Lower ApoA1 is linked to a higher chance of heart attack and stroke over time, and higher ApoA1 to a lower chance. In a large Swedish study (AMORIS), ApoA1 was protective and ApoB was a stronger risk predictor than LDL cholesterol. Even so, ApoA1 is not a treatment target in the 2018 US cholesterol guideline summary, so clinicians use it as extra context next to your cholesterol results. It also helps in work-ups for rare inherited low-HDL conditions.

If it’s low

A lower ApoA1 usually goes along with a lower HDL cholesterol and is linked to a higher chance of heart disease over time. The most common reasons are everyday ones such as smoking, extra weight, blood sugar that is not well controlled and some medicines. Rare inherited conditions can cause very low levels.

Common causes

  • Smoking or other tobacco use
  • Extra weight, low physical activity, insulin resistance or diabetes that is not well controlled
  • Chronic kidney disease
  • Some medicines, including beta-blockers, diuretics, androgens and progestins
  • Rare inherited conditions such as familial hypoalphalipoproteinemia or Tangier disease

What can help

  • Not smoking, and regular physical activity, are linked to higher ApoA1; ask your clinician for support if you smoke
  • Losing extra weight is linked to higher ApoA1
  • Ask your clinician whether a medicine you take could be lowering it
  • Ask whether your blood sugar and kidney function are worth checking

If it’s high

A higher ApoA1 is usually not a problem and often goes along with a higher HDL cholesterol. It can run in families, and several everyday things and medicines can raise it.

Common causes

  • A family tendency to higher HDL and ApoA1
  • Regular physical activity
  • Weight loss
  • Pregnancy
  • Estrogen-containing medicines, including birth control pills
  • Some cholesterol-lowering medicines and niacin, and a few other medicines such as carbamazepine

What can help

  • A high ApoA1 on its own usually does not need action
  • Ask your clinician whether any medicine or supplement you take could explain it

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

What can affect your result

  • Sex: women usually have higher ApoA1 than men
  • Smoking, body weight and physical activity
  • Medicines such as estrogens, beta-blockers, diuretics, androgens and progestins
  • Pregnancy
  • Kidney disease and blood sugar control
  • Lab method: different labs publish different ranges
  • Methods and labs differ (turbidimetric immunoassay, nephelometry), and ARUP, UW Medicine and Mayo publish different ranges, so compare a result with the range from the same lab.
  • Labs may flag very cloudy (lipemic) samples, which can disturb turbidity-based methods.
  • Some medicines can raise ApoA1 (estrogens, including birth control pills, and some cholesterol medicines) or lower it (beta-blockers, diuretics, androgens and progestins); pregnancy raises it (Pathology Tests Explained).

When to talk to a clinician

ApoA1 is not an urgent test. Raise a result that is below your lab's range at your next routine visit, especially if your HDL cholesterol is also low or heart disease runs in your family. A result far below your lab's range is worth a closer look because rare inherited conditions can be the cause. If you have chest pain, trouble breathing or fainting, call 911 or your local emergency number, whatever your results are.

Questions you could ask

  • Is ApoA1 useful for me, given my family history and my other lipid results?
  • How often should we repeat my lipid tests?
  • Could a medicine or supplement I take explain a higher ApoA1?
  • Does my ApoA1 fit with my HDL cholesterol?
  • Could any of my medicines or health conditions be lowering it?
  • Would ApoB or other lipid tests add useful information for me?

Questions people ask

How is ApoA1 different from HDL cholesterol?

HDL cholesterol measures the cholesterol carried inside HDL particles. ApoA1 measures the main protein on those particles, so it is a rough guide to how much HDL you have. The two usually rise and fall together. Some experts think particle-based measures can describe risk better than the cholesterol amount, but ApoA1 does not replace your standard lipid tests.

Why does my lab's range differ from one I read online?

ApoA1 is not harmonized between labs. ARUP, UW Medicine and Mayo all print different numbers, and some give only a lower cutoff. Women have higher levels than men, so ranges are often split by sex. Use the range printed on your own report, and compare later results with the same lab.

How do I convert ApoA1 between mg/dL and g/L?

Divide mg/dL by 100 to get g/L. For example, 150 mg/dL is 1.5 g/L. To go the other way, multiply g/L by 100.

Show the science and sources

Units

  • 1 mg/dL = 1 mg/dL
  • 1 mg/dL = 0.01 g/L

Open the ApoA1 unit converter

Is a change real?

ApoA1 naturally varies about 4.8% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 14% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: The European Biological Variation Study (EuBIVAS): a summary report.

For clinicians and researchers

ApoA1 is the main structural protein of HDL, made in the liver and small intestine. It shapes the particle and takes part in reverse cholesterol transport. HDL particles usually carry two to five ApoA1 molecules, so ApoA1 reflects HDL protein mass rather than a particle count, unlike ApoB. Reference labs measure it by turbidimetric immunoassay (Mayo, ARUP) or nephelometry (UW Medicine's in-house assay) and report mg/dL. Published intervals differ: ARUP lists 104-202 mg/dL for men and 108-225 for women, UW's in-house nephelometric assay lists 107-187 and 115-206, and Mayo lists cutoffs of 120 or higher for men and 140 or higher for women (children 2-17: low under 115, borderline 115-120, acceptable over 120). Very low values can point to Tangier disease and related inherited disorders, which is a listed use of the test at Mayo. ApoA1 is also one of five inputs to the FibroTest/FibroSure fibrosis score, where it is weighted by age and sex. In AMORIS (175,553 people), ApoA-I was protective against fatal myocardial infarction and ApoB/ApoA-I added predictive value. The 2018 AHA/ACC cholesterol guideline summary mentions ApoB but does not use ApoA1. A molar LOINC code exists (76483-7), but labs rarely report ApoA1 in mol/L, so only mg/dL and g/L are converted.

LOINC 1869-7 (primary), 76483-7. Specimen: serum-or-plasma.

Sources

  1. Apolipoprotein B/A Ratio (test 0050028), including the Apolipoprotein A-1 reference interval, ARUP Laboratories
  2. Apolipoprotein A1 (APOA1), UW Medicine Laboratory Test Guide, University of Washington Medicine, Department of Laboratory Medicine and Pathology
  3. Apolipoprotein A1, Serum (test APOA1), Mayo Clinic Laboratories (Extended Catalog)
  4. Apolipoprotein A-1, Pathology Tests Explained (Royal College of Pathologists of Australasia) (2025)
  5. Apolipoprotein A1 (ApoA1), Cleveland Clinic (2025)
  6. High apolipoprotein B, low apolipoprotein A-I, and improvement in the prediction of fatal myocardial infarction (AMORIS study): a prospective study, The Lancet (2001)
  7. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol: Executive Summary, Circulation (2019)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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