Skip to content
Blood Test Tracker

HDL Particle Number (HDL-P)

The number of HDL particles in your blood, counted by NMR. It sits beside HDL cholesterol, which measures the cholesterol those particles carry.

AI-verified against cited sources. Awaiting expert reviewAlso called HDL-PLOINC 49748-7

Check your result

Sex (optional)

Type your result to see where it falls.

Nothing you type here leaves your browser.

What it is

HDL cholesterol (HDL-C) tells you how much cholesterol is inside your HDL particles. HDL particle number (HDL-P) counts the particles themselves. Labcorp and Mayo Clinic Laboratories measure it with nuclear magnetic resonance (NMR), and some other labs use a method called ion mobility. The methods count a little differently, so use the same lab and method when you compare results over time.

Why it matters

In a large US study (MESA), people with more HDL particles had less plaque in the neck arteries and fewer heart events, and the link held even after accounting for HDL cholesterol and LDL particles. But medicines that raise HDL haven't been shown to prevent heart attacks, and in another large trial (JUPITER) HDL subgroups measured by ion mobility did not predict first heart events. A 2026 Circulation review also says the current ACC/AHA guideline recommends against NMR testing beyond the standard lipid panel, apoB and Lp(a). HDL-P is best seen as extra context, not a number to chase.

If it’s low

A lower count means fewer HDL particles. It often goes with low HDL cholesterol, higher triglycerides, extra weight and insulin resistance. In studies, lower counts were linked to more artery plaque and more heart events over time, but the link is modest and still debated. It can't tell you whether you have heart disease.

Common causes

  • Insulin resistance, prediabetes, type 2 diabetes or metabolic syndrome
  • Higher triglycerides
  • Extra body weight and little physical activity
  • Family history and genes
  • Some medicines

What can help

  • Be active most days. Exercise is linked to higher HDL cholesterol
  • If you carry extra weight, ask your clinician about a realistic goal
  • Ask whether LDL cholesterol, apoB, non-HDL cholesterol, triglycerides or blood sugar would be a more useful way to follow your heart health
  • Ask whether any of your medicines can lower HDL

If it’s high

A higher count means more HDL particles are circulating. It usually causes no symptoms. In studies, higher counts went with less artery plaque and fewer heart events. Even so, a high number is not a goal to chase, because treatments that raise HDL haven't been shown to prevent heart attacks.

Common causes

  • Being female, since women usually run higher than men
  • Regular physical activity
  • Alcohol intake, which raises HDL cholesterol
  • Family history and genes

What can help

  • Ask your clinician how this result fits with your LDL cholesterol, apoB 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.

The usual range depends on sex and age. Choose women or men to see the one that applies.

See HDL-P by age and sex, with the U.S. survey numbers where they exist.

What can affect your result

  • Sex: women usually run higher, and Mayo Clinic Laboratories uses a higher cutoff for women (above 35 µmol/L) than for men (above 30 µmol/L)
  • Method: NMR (Labcorp, Mayo) and ion mobility count HDL particles differently, so numbers and ranges differ between labs
  • Fasting: Labcorp asks for 8 hours and Mayo requires 12 hours, with no alcohol for 24 hours
  • Triglycerides, insulin resistance, diabetes and body weight
  • Physical activity and alcohol, which both raise HDL cholesterol
  • Family history and genes
  • Labcorp asks for an 8-hour fast for its NMR LipoProfile tests, and Mayo Clinic Laboratories requires a 12-hour fast with no alcohol for 24 hours before the draw. Follow the instructions your lab gives you.
  • NMR and ion mobility count HDL particles differently, so results and ranges are not interchangeable between labs. Compare results only within the same lab and method.
  • Units differ within one report: Labcorp prints HDL-P in µmol/L but LDL-P in nmol/L, and 1 µmol/L equals 1,000 nmol/L.
  • Labcorp rejects samples that are grossly hemolyzed, contaminated with red cells, or held too long at room temperature. Mayo does not accept gel-barrier (SST) tubes for this test.

When to talk to a clinician

An HDL-P result by itself rarely needs urgent attention. Talk with a clinician if your count is below your lab's range, especially if you have diabetes, a family history of early heart disease or other risk factors. 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 NMR particle testing useful for me, given current guidelines?
  • Should I use the same lab and method each time so my results can be compared?
  • Does a higher particle count change anything for my heart-health plan, or can I rely on my other results?
  • Could my triglycerides, weight or blood sugar explain a low count?
  • Would apoB or non-HDL cholesterol be a more useful way for us to follow my heart health?
  • When should we recheck, and what would you like to see change by then?

Questions people ask

What is the difference between HDL-C and HDL-P?

HDL-C is the amount of cholesterol carried inside your HDL particles, in mg/dL. HDL-P is the number of HDL particles, in µmol/L. The two usually move together, but they do not always agree.

Does a high HDL-P mean I'm protected from heart disease?

Not necessarily. In studies, a higher count went with fewer heart events, but medicines that raise HDL haven't been shown to prevent heart attacks. HDL-P is one piece of information, and your clinician looks at it with your LDL cholesterol, apoB, blood pressure and other risk factors.

Why do Labcorp and Mayo list different cutoffs?

Labcorp uses one cutoff of 30.5 µmol/L, the median of its reference group. Mayo Clinic Laboratories uses one cutoff for men (above 30) and another for women (above 35). Each lab sets its own range, so use the range printed on your own report.

Show the science and sources

Units

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

Open the HDL-P unit converter

For clinicians and researchers

HDL-P is the molar concentration of HDL particles in µmol/L. Labcorp and Mayo Clinic Laboratories measure it by proton NMR, where signals from lipid methyl groups are deconvoluted into lipoprotein subclasses by size, while ion mobility, as used in JUPITER, counts particles after gas-phase size separation. Labcorp's cutoff of 30.5 µmol/L is the median of its LipoScience reference group (4,588 adults without known CVD or diabetes and not on lipid medication; 25th and 75th percentiles 26.7 and 34.9 µmol/L). Mayo gives sex-specific cutoffs for adults of above 30 µmol/L for men and above 35 µmol/L for women. In MESA (5,598 adults aged 45 to 84, no baseline coronary disease, 227 events over a mean of 6 years), HDL-C and HDL-P correlated at ρ = 0.69. Per 1 SD higher HDL-P (6.64 µmol/L) the hazard ratio for coronary heart disease was 0.70 (95% CI 0.59-0.82). After adjusting for each other and for LDL-P, HDL-P stayed associated with coronary events (HR 0.75, 0.61-0.93) and carotid wall thickness, while HDL-C did not (HR 0.97, 0.77-1.22). In JUPITER's placebo arm, ion mobility HDL subfractions were not associated with first CVD events. A 2026 Circulation review notes that HDL-raising therapies have generally failed to reduce ASCVD, so HDL-C is read as a risk marker rather than a target, and that the current ACC/AHA guideline recommends against NMR and other advanced lipoprotein testing beyond the lipid panel, apoB and Lp(a). Labcorp and Mayo both map their HDL particle result to LOINC 49748-7 (LOINC uses 'Lipoprotein.alpha', the electrophoretic name for the HDL fraction). The tests are laboratory-developed tests that the FDA has not cleared or approved.

LOINC 49748-7 (primary). Specimen: serum-or-plasma.

Sources

  1. NMR LipoProfile+Lipids+Graph, sample patient report (test 123810), Labcorp (2024)
  2. NMR LipoProfile With Lipids (With Graph) (Labcorp test 123810), Labcorp (2026)
  3. Nuclear Magnetic Resonance Lipoprotein Profile, Serum (test NMRLP), Mayo Clinic Laboratories (2026)
  4. High-density lipoprotein cholesterol and particle concentrations, carotid atherosclerosis, and coronary events: MESA, Journal of the American College of Cardiology (2012)
  5. 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)
  6. Lipid Profile Testing and Interpretation (summarizes the 2026 ACC/AHA Dyslipidemia Guideline), Circulation (Nguyen, Ahmad, Navar) (2026)
  7. LOINC 49748-7 Lipoprotein.alpha [Moles/volume] in Serum or Plasma, Regenstrief Institute (LOINC)

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

Related markers