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Large HDL Particle Number

The number of large HDL particles in your blood. Labs mainly use it as one input to an insulin-resistance score, not as a stand-alone heart test.

AI-verified against cited sources. Awaiting expert reviewAlso called Large HDL-PLOINC 43729-3

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What it is

Your HDL ("good" cholesterol) particles come in different sizes. NMR tests count them and sort them by size, and the biggest group is called large HDL. Labcorp reports this count in micromoles per liter (µmol/L). Quest's ion mobility test reports a large HDL count too, but the method and the ranges differ, so don't compare numbers between labs. The count is not the same as your HDL cholesterol, which is the cholesterol carried by all HDL particles together.

Why it matters

Labcorp uses large HDL particles as one of six measurements in its LP-IR score, an index of insulin resistance. In a large US study (MESA), people with fewer large HDL particles were more likely to develop type 2 diabetes in the following years. For heart disease the picture is less clear. Quest notes that a low large HDL count has historically been linked to higher heart risk, but in the JUPITER trial, ion mobility HDL subfractions, including large HDL, were not linked to heart events in the placebo group. A 2026 Circulation review says the current ACC/AHA guideline recommends against NMR particle testing beyond a standard lipid panel, apoB and Lp(a). So this number is best read as a clue about metabolism, next to your other results.

If it’s low

A lower count is the direction Labcorp's scale treats as more insulin resistance. It is common, and it often goes along with high triglycerides, extra weight and insulin resistance. It is not a diagnosis. Your clinician can look at it with your blood sugar, triglycerides and other results.

Common causes

  • Insulin resistance, prediabetes or type 2 diabetes
  • High triglycerides
  • Extra body weight, especially around the middle
  • Little physical activity
  • Cigarette smoking

What can help

  • Be active most days. Physical activity can raise HDL cholesterol and lower triglycerides
  • If you smoke, ask your clinician about help quitting
  • If you carry extra weight, ask your clinician about a realistic goal
  • Eat less added sugar and refined carbohydrate, and swap saturated fats for healthier fats
  • Ask your clinician whether a blood sugar test such as fasting glucose or A1c is worth checking

If it’s high

A higher count is the direction Labcorp's scale treats as lower risk, and it tends to go with better insulin sensitivity. A high result is usually not a concern on its own. Your clinician can look at it with your triglycerides, blood sugar and other results.

Common causes

  • Good insulin sensitivity and lower triglycerides
  • Regular physical activity, which can raise HDL cholesterol
  • Inherited differences that raise HDL

What can help

  • A high result usually needs no action
  • If it is unusually high, ask your clinician how it fits with your HDL cholesterol and other results

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.

For adults: 4.8 and above µmol/L. Source: Labcorp.

  • Adults (this one applies)4.8 and above µmol/L

    Source: Labcorp

What can affect your result

  • Method: NMR and ion mobility group HDL by size differently, so counts and ranges differ between labs
  • Fasting: Labcorp asks for an 8-hour fast
  • Insulin resistance, diabetes, triglycerides and body weight
  • Physical activity, smoking and diet
  • Inherited differences in HDL
  • Unit: µmol/L at Labcorp, and possibly nmol/L on other reports (1 µmol/L = 1,000 nmol/L)
  • Labcorp asks for an 8-hour fast for the NMR LipoProfile, and it states that the related LP-IR score is inaccurate on a non-fasting sample. Quest's ion mobility test says fasting is preferred but not required.
  • NMR and ion mobility sort HDL particles into size groups differently, so counts and ranges are not interchangeable between labs.
  • Units differ within one report: Labcorp prints large HDL-P in µmol/L but its LDL-P, small LDL-P and large VLDL-P in nmol/L, and other reports may print nmol/L (1 µmol/L = 1,000 nmol/L).
  • Labcorp rejects samples that are grossly hemolyzed, contaminated with red cells, or held too long at room temperature.

Weeks to months. It follows changes in insulin sensitivity, triglycerides, physical activity and weight.

When to talk to a clinician

No large HDL value is an urgent result on its own. Bring a result below your lab's range to your next routine visit, especially if you have extra weight, a family history of diabetes or high blood sugar. If you have chest pain or pressure, trouble breathing, or signs of a stroke such as face drooping, arm weakness or trouble speaking, call 911 or your local emergency number, whatever your results are.

Questions you could ask

  • Is this test useful for me, or would my standard lipid panel and apoB tell us what we need?
  • Should I use the same lab and method each time so my results can be compared?
  • Does my large HDL count point to anything I should look at with my blood sugar or triglycerides?
  • Would an A1c or fasting glucose test be useful for me?

Questions people ask

Is large HDL the same as my HDL cholesterol?

No. HDL cholesterol is the cholesterol carried by all of your HDL particles. Large HDL-P counts only the biggest HDL particles. They are separate measurements, so one can look different from the other.

Why are some of my particle counts in µmol/L and others in nmol/L?

On Labcorp's NMR LipoProfile, total HDL-P and large HDL-P are printed in micromoles per liter (µmol/L), while LDL-P, small LDL-P and large VLDL-P are printed in nanomoles per liter (nmol/L). One µmol/L equals 1,000 nmol/L, so check the unit before you compare numbers.

What does a result below 4.8 µmol/L mean?

Labcorp's 4.8 µmol/L is the median of its reference group, so about half of the people in that group are below it. A lower result is not a diagnosis. It is a clue your clinician may look at with your triglycerides, blood sugar and other results.

Show the science and sources

Units

  • 1 µmol/L = 1 µmol/L
  • 1 µmol/L = 1000 nmol/L

Open the Large HDL-P unit converter

For clinicians and researchers

Large HDL-P is the molar concentration of HDL particles in the largest NMR size class. In the LipoProfile-3 algorithm used in the LP-IR publication, large HDL-P spans 9.4-14 nm (small LDL-P 18.0-20.5 nm, large VLDL-P above 60 nm). The vendor's current algorithm and ion mobility's size bins may differ, so values are not interchangeable. Labcorp prints the count in µmol/L with a reference of 4.8 µmol/L or more, the median of its 4,588-person LipoScience reference group (25th and 75th percentiles 3.1 and 7.3 µmol/L). In the original LP-IR algorithm large HDL-P carries 12 of 100 points (VLDL size 32, large VLDL-P 22, HDL size 20, small LDL-P 8, LDL size 6). In that paper large HDL-P correlated with HOMA-IR at r = -0.40 and with glucose disposal rate at r = 0.47. In MESA (5,314 adults), lower large HDL-P was associated with incident type 2 diabetes after adjustment for confounders and for glucose or insulin. For CVD the evidence is mixed: in JUPITER's placebo arm, ion mobility large HDL-P was not associated with first CVD events (HR 0.97 per SD, 95% CI 0.85-1.12), while Quest cites an earlier Malmo cohort association. A 2026 Circulation review states that the current ACC/AHA guideline recommends against NMR and other advanced lipoprotein testing beyond the lipid panel, apoB and Lp(a). Labcorp's test is a laboratory-developed test that the FDA has not cleared or approved.

LOINC 43729-3 (primary). Specimen: serum-or-plasma.

Sources

  1. NMR LipoProfile+IR+Graph, sample patient report (test 123497), Labcorp (2024)
  2. NMR LipoProfile With Insulin Resistance Markers, Without Lipids (With Graph) (test 123497), Labcorp
  3. Cardio IQ Lipoprotein Fractionation Ion Mobility: clinical education FAQ, Quest Diagnostics
  4. Cardio IQ Lipoprotein Fractionation, Ion Mobility (test 91604), Quest Diagnostics
  5. Lipoprotein insulin resistance index: a lipoprotein particle-derived measure of insulin resistance, Metabolic Syndrome and Related Disorders (2014)
  6. Lipoprotein particles and incident type 2 diabetes in the Multi-Ethnic Study of Atherosclerosis, Diabetes Care (2015)
  7. Atherogenic lipoprotein subfractions determined by ion mobility and first cardiovascular events after random allocation to high-intensity statin or placebo: the JUPITER trial, Circulation (2015)
  8. Lipid Profile Testing and Interpretation (summarizes the 2026 ACC/AHA Dyslipidemia Guideline), Circulation (Nguyen, Ahmad, Navar) (2026)
  9. Blood Cholesterol: Treatment (lifestyle changes), National Heart, Lung, and Blood Institute
  10. Triglycerides, MedlinePlus (National Library of Medicine)

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

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