Lab result explainedCholesterol and lipidsLast updated November 11, 2026

LDL particle number (LDL-P): normal range, small dense LDL and what a high NMR LipoProfile result means

LDL particle number (LDL-P) · NMR LipoProfile or advanced lipoprotein panel · reported in nmol/L for particle counts; nm for particle size; small dense LDL cholesterol (a different test) in mg/dL

LDL particle number (LDL-P) is a count of how many low-density lipoprotein particles are circulating in your blood, rather than how much cholesterol they are carrying. It is measured by nuclear magnetic resonance (NMR) spectroscopy on a test usually called the NMR LipoProfile, and reported in nanomoles per liter (nmol/L). An LDL-P under 1,000 nmol/L is optimal, 1,000–1,299 is near optimal, 1,300–1,599 borderline high, 1,600–2,000 high and above 2,000 very high. The same report usually gives small LDL particle number, average LDL particle size and an insulin-resistance score.

The reason anyone orders it is that a standard LDL cholesterol (LDL-C) and the particle count can disagree. Plaque formation depends on how many LDL particles cross into the artery wall, and each particle can carry a variable amount of cholesterol. When particles are small and cholesterol-poor, which is typical with high triglycerides, low HDL, excess abdominal fat, prediabetes and type 2 diabetes, a person can have a normal-looking LDL-C of 100 mg/dL while carrying 1,600 or more particles. In the Framingham Offspring and MESA studies, when LDL-C and LDL-P disagreed, risk followed the particle number.

LDL-P is not part of routine screening and is not required by US cholesterol guidelines, which use apolipoprotein B (one apoB per atherogenic particle) for the same purpose because it is cheaper and standardized. LDL-P is most useful in people with metabolic syndrome or diabetes, people with a borderline LDL-C and a family history of early heart disease, and people on treatment whose LDL-C has fallen but who still want to know whether their particle burden has.

LDL-P at a glance

  • What it is: the number of LDL particles per liter of plasma, measured by NMR; it reflects particle burden rather than cholesterol content.
  • Normal (NMR LipoProfile): under 1,000 nmol/L optimal; 1,000–1,299 near optimal; 1,300–1,599 borderline high; 1,600–2,000 high; above 2,000 very high.
  • Small LDL-P: under about 530 nmol/L is desirable; LDL size above 20.5 nm is pattern A (large, buoyant) and 20.5 nm or less is pattern B (small, dense).
  • Rough equivalents: LDL-P 1,000 is about LDL-C 100 mg/dL and apoB 80; LDL-P 1,600 is about LDL-C 160 and apoB 110.
  • A high LDL-P with a normal LDL-C (discordance) is common with high triglycerides, low HDL, obesity and diabetes, and risk follows the LDL-P.
  • Next step: treat it like a high LDL-C with extra attention to insulin resistance; weight loss, cutting refined carbohydrate, exercise, fiber and, when risk warrants, a statin all lower particle number.

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What LDL-P measures

Every lipoprotein particle gives off a characteristic NMR signal from the methyl groups of the lipids it contains, and the amplitude of that signal is proportional to the number of particles of each size. The NMR LipoProfile deconvolutes the combined signal from a blood sample into counts of VLDL, LDL and HDL particles in several size classes. Total LDL-P is the sum of large and small LDL (plus IDL), small LDL-P is the count of particles in the smallest size bands, and LDL size is the signal-weighted average diameter in nanometers. Ion-mobility is a different technology, offered by some US labs, that physically separates particles by size and counts them; its reference ranges are different and the two methods are not interchangeable.

The cut-points come from population percentiles in the Framingham Offspring and MESA cohorts: an LDL-P of 1,000 nmol/L sits at about the 20th percentile of US adults, the same percentile as an LDL-C of 100 mg/dL, and 1,600 nmol/L at about the 80th, matching an LDL-C of 160. Apolipoprotein B measures the same particle count by immunoassay (because each LDL, VLDL and IDL particle carries exactly one apoB), so an apoB of 80 mg/dL corresponds to an LDL-P of roughly 1,000 and apoB 110 to roughly 1,600; apoB includes VLDL particles, LDL-P does not.

Most reports also print an LP-IR score (0 to 100), which combines VLDL, LDL and HDL particle sizes and counts into an index of insulin resistance; under 45 is considered insulin-sensitive and above 63 insulin-resistant. Fasting is not strictly required for LDL-P itself, but triglyceride-rich particles rise after meals and shift particle sizes, so most labs ask for a 9 to 12 hour fast to make the whole profile interpretable.

Normal range for LDL-P

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

GroupTypical range (nmol/L for particle counts; nm for particle size; small dense LDL cholesterol (a different test) in mg/dL)Notes
LDL-P, optimalBelow 1,000 nmol/LAbout the 20th percentile of US adults; the goal for people with established heart disease or diabetes. Labs differ; use the printed range.
LDL-P, near or above optimal1,000–1,299 nmol/LComparable to LDL-C 100–129 mg/dL; the goal for moderate-risk adults is under 1,300.
LDL-P, borderline high1,300–1,599 nmol/LComparable to LDL-C 130–159 mg/dL.
LDL-P, high1,600–2,000 nmol/LAbout the 80th to 95th percentile; comparable to LDL-C 160–189 mg/dL.
LDL-P, very highAbove 2,000 nmol/LAbove the 95th percentile; with LDL-C above 190 suggests familial hypercholesterolemia.
Small LDL-PBelow about 530 nmol/L desirable; above about 850 highCut-points vary by lab version; small particles track triglycerides and insulin resistance.
LDL particle sizeAbove 20.5 nm = pattern A (large); 20.5 nm or below = pattern B (small, dense)Size is less predictive than particle number once LDL-P is known.
Small dense LDL cholesterol (direct assay, different test)Roughly below 40–50 mg/dLIn the ARIC study the highest quartile (above about 50 mg/dL) carried about 50 percent more coronary risk. Reference ranges differ between labs.
LP-IR scoreBelow 45 insulin-sensitive; 45–63 intermediate; above 63 insulin-resistantDerived from the same NMR scan.

High LDL particle number

A high LDL-P means more LDL particles are available to enter the artery wall, and particle number is what drives plaque formation. In the Framingham Offspring Study, people in the highest LDL-P tertile had roughly two to three times the cardiovascular event rate of those in the lowest, and the gradient was steeper than for LDL cholesterol. In MESA, when LDL-P and LDL-C disagreed, carotid wall thickness and later events followed LDL-P: people with a low LDL-C but a high LDL-P had the same risk as people whose LDL-C was high.

How you got there matters. If LDL-P and LDL-C are both high and in proportion (for example LDL-C 170 and LDL-P 1,700) the problem is simply too much LDL, from diet, genetics, hypothyroidism or medications, and it is managed like any high LDL. If LDL-P is high but LDL-C looks acceptable, each particle is carrying less cholesterol than usual, which almost always means the particles are small and dense and that the underlying driver is insulin resistance: high triglycerides, low HDL, a large waist, fatty liver or prediabetes. The small LDL-P, triglyceride and LP-IR values on the same report will usually confirm this.

LDL-P is not a diagnosis and not in itself a treatment threshold in US guidelines. It is a refinement: a high LDL-P in someone whose LDL-C put them in a borderline category justifies treating them as higher risk, and a persistently high LDL-P on statin treatment despite a good LDL-C is a reason to intensify lifestyle change or add therapy rather than declare the job done. Apolipoprotein B, which guidelines do recognize (130 mg/dL or more is a risk enhancer), will give the same answer and is often used to confirm it.

Common causes

  1. Insulin resistance, metabolic syndrome and type 2 diabetes

    High insulin and excess free fatty acids make the liver secrete more, larger VLDL; exchange of triglyceride for cholesterol between VLDL and LDL, followed by lipase action, leaves many small, cholesterol-poor LDL particles. This is the commonest reason for a high LDL-P with a normal LDL-C.

  2. High triglycerides from any cause

    Triglycerides above 150 mg/dL drive the same remodeling; above 200 the discordance between LDL-C and LDL-P becomes the rule rather than the exception. Alcohol, sugar-sweetened drinks and refined carbohydrate are common dietary drivers.

  3. Excess abdominal fat and non-alcoholic fatty liver

    Visceral fat and a fatty liver both over-produce VLDL. Small LDL-P and LP-IR score rise with waist circumference even when weight is only modestly elevated.

  4. Diet high in saturated and trans fat

    Reduces LDL receptor activity in the liver, so particles of every size circulate longer; this raises LDL-C and LDL-P together.

  5. Familial hypercholesterolemia and familial combined hyperlipidemia

    Inherited LDL receptor or apoB defects give LDL-P above 2,000 nmol/L from childhood. Familial combined hyperlipidemia characteristically produces high apoB and LDL-P with variable LDL-C and triglycerides and a family history of early heart attacks.

  6. Hypothyroidism

    Thyroid hormone up-regulates LDL receptors; an underactive thyroid raises LDL-P in step with LDL-C and both normalize once TSH does.

  7. Polycystic ovary syndrome and menopause

    PCOS combines insulin resistance with androgen excess and typically shows small dense LDL and raised LDL-P; after menopause the loss of estrogen raises LDL-P by 10 to 20 percent.

  8. Kidney disease and nephrotic syndrome

    Impaired clearance of triglyceride-rich particles and, in nephrotic syndrome, massive hepatic lipoprotein over-production raise particle counts of all classes.

  9. Medications

    Thiazides, some beta blockers, oral corticosteroids, anabolic steroids, isotretinoin, some antiretrovirals and second-generation antipsychotics raise triglycerides or LDL and with them LDL-P.

  10. Smoking

    Smokers have smaller LDL particles and higher small LDL-P than non-smokers, with a shift back toward larger particles within months of quitting.

Symptoms that can go with it

  • None; a high particle number causes no symptoms, and most people learn of it from a routine or advanced lipid panel
  • Chest pressure on exertion if coronary plaque has become significant
  • Leg pain on walking that resolves with rest (peripheral artery disease)
  • Signs of insulin resistance that often travel with small dense LDL: increased waist size, darkened skin folds (acanthosis nigricans), skin tags, fatigue after meals
  • Tendon xanthomas or corneal arcus before 45 if the cause is familial hypercholesterolemia
  • Transient neurological symptoms (weakness, speech or vision disturbance) from carotid plaque

Low LDL particle number

There is no lower limit of concern for LDL-P. Values under 1,000 nmol/L are the goal for people at high risk, and values of 500 to 800 are routine on statin, ezetimibe or PCSK9 inhibitor therapy and in people with lifelong genetic low LDL. Outcome trials that drove apoB and LDL-C to very low levels have not shown harm from the low lipid level itself, and populations with naturally low LDL-P have less coronary disease.

The one useful question is whether a low LDL-P is discordant in the other direction: an LDL-C that looks high (say 150) with an LDL-P that is only 1,100 means the particles are large and cholesterol-rich, which is the pattern A profile seen in some lean, active, insulin-sensitive people. Their risk is closer to what the particle number suggests than what the LDL-C suggests, which is one of the legitimate reasons to order the test before committing to lifelong medication.

Common causes

  1. Lipid-lowering medication

    Statins lower LDL-P by 25 to 45 percent, somewhat less than they lower LDL-C, which is why LDL-P can remain above goal when LDL-C is at goal. Ezetimibe and PCSK9 inhibitors lower particle number in proportion to LDL-C.

  2. Insulin-sensitive, lean phenotype

    Low triglycerides and high HDL go with large, cholesterol-rich LDL particles, so LDL-P is lower than the LDL-C would predict.

  3. Plant-based and Mediterranean dietary patterns

    Diets low in saturated fat and high in fiber, nuts and unsaturated fat lower apoB and LDL-P by 5 to 15 percent in trials.

  4. Genetic variants (PCSK9 loss-of-function, hypobetalipoproteinemia)

    Lifelong LDL-P 30 to 40 percent below average with a markedly lower lifetime coronary risk.

  5. Hyperthyroidism, malabsorption, chronic illness and liver disease

    The same conditions that lower LDL-C lower LDL-P; an unexplained fall from a previously higher level should prompt a look for these.

Symptoms that can go with it

  • None; a low LDL-P does not cause symptoms
  • Weight loss, tremor, heat intolerance or palpitations if hyperthyroidism is the reason
  • Diarrhea, bloating or weight loss if malabsorption is the reason
  • Fatigue or jaundice if advanced liver disease is the reason
  • No symptoms at all in people whose low LDL-P is from medication, diet or genetics

Read it alongside

  • Apolipoprotein B — the standardized, guideline-endorsed particle count; apoB 130 mg/dL or more is a risk enhancer and should match the LDL-P story.
  • LDL cholesterol — compare the two to spot discordance; LDL-C 100 should go with LDL-P about 1,000.
  • Triglycerides — the main driver of small, dense particles; above 150 mg/dL expect LDL-P to run higher than LDL-C suggests.
  • HDL cholesterol and HDL particle number — low HDL with high triglycerides is the insulin-resistant pattern that produces high small LDL-P.
  • Small LDL-P and LDL size — on the same report; mostly useful as a flag for insulin resistance once total LDL-P is known.
  • A1C, fasting insulin or HOMA-IR — confirm or exclude the insulin resistance that a high small LDL-P or LP-IR score implies.
  • Lipoprotein(a) — a separate, inherited particle that adds risk; measure once in a lifetime.
  • TSH — hypothyroidism raises LDL-P and is reversible.

What usually happens next

  1. Compare LDL-P with your LDL-C and apoB; if all three are high and in proportion, the problem is LDL quantity and is managed as a high LDL. If LDL-P is high with a normal LDL-C, look at triglycerides, small LDL-P and LP-IR, and ask for an A1C and liver enzymes to assess insulin resistance and fatty liver.
  2. Ask your clinician to recalculate your 10-year risk treating the LDL-P result as a risk enhancer; this is how it changes decisions in practice.
  3. If LDL-P is above 2,000 nmol/L, ask about familial hypercholesterolemia or familial combined hyperlipidemia, and whether first-degree relatives should have a lipid panel.
  4. Expect a repeat in 3 to 6 months after lifestyle changes or starting treatment; LDL-P responds to weight loss and carbohydrate restriction within weeks, and a repeat apoB is an acceptable, cheaper way to track it.
  5. Check whether insurance covers NMR testing before repeating it; apoB is covered more widely and tracks the same particle burden.

Diet, lifestyle and natural levers with evidence

What can move LDL-P once the cause is known. Nothing here replaces finding the cause.

Weight loss and reduced refined carbohydrate

Moderate evidence

In a controlled feeding study, cutting carbohydrate from 54 to 26 percent of calories reduced small LDL particles and shifted pattern B toward pattern A even before weight loss, and a 5 to 10 percent weight loss reduced small LDL-P further regardless of diet composition. Weight loss of 10 kg typically lowers triglycerides by 15 to 30 mg/dL and total LDL-P by 10 to 15 percent; the effect is largest in people whose LDL-P is discordantly high.

Very low carbohydrate diets that are high in saturated fat can raise LDL-C and LDL-P in a subset of lean people; recheck after 3 months rather than assuming.

Aerobic exercise, higher volume

Moderate evidence

In the STRRIDE randomized trial, the equivalent of jogging about 20 miles a week for 8 months reduced LDL particle concentration, reduced small LDL particles and increased average LDL size, while a lower volume of walking had smaller effects; LDL-C itself barely changed, which illustrates why LDL-P is a more sensitive readout of exercise benefit. Intensity mattered less than total amount.

Viscous soluble fiber (psyllium, oats, barley, legumes)

Moderate evidence

About 10 g of psyllium a day lowered apoB by about 5 percent and LDL cholesterol by 13 mg/dL in a meta-analysis of 28 randomized trials; because fiber lowers the particle count rather than shrinking particles, LDL-P falls in parallel. Oat beta-glucan at 3 g a day has a similar, slightly smaller effect, and in a small trial also reduced small dense LDL.

Separate psyllium from medications by 2 hours and increase gradually with water to limit bloating.

Omega-3 fatty acids (EPA and DHA)

Moderate evidence

Prescription-strength omega-3 (2 to 4 g of EPA plus DHA a day) lowers triglycerides by 20 to 30 percent and shifts LDL toward larger particles; in the ANCHOR trial, 4 g a day of purified EPA lowered apoB by 9 percent and did not raise LDL-C, whereas DHA-containing formulations can raise LDL-C by 5 to 10 percent while still lowering particle number. Over-the-counter fish oil at 1 g a day has little effect on LDL-P.

High doses increase bleeding tendency with anticoagulants and were associated with more atrial fibrillation in outcome trials; discuss before exceeding 1 g a day of EPA plus DHA.

Replace saturated fat with unsaturated fat and nuts

Strong evidence

Replacing saturated fat with polyunsaturated fat lowers LDL-C by about 1.8 mg/dL per percent of calories swapped and lowers apoB and LDL-P proportionally; a meta-analysis of 61 trials found each daily ounce of tree nuts lowered apoB by 3.7 mg/dL, equivalent to roughly 40 to 50 nmol/L of LDL-P. The Portfolio diet (nuts, soy, plant sterols and viscous fiber) lowered LDL-C by 13 to 17 percent and apoB by a similar fraction over six months.

When to see a clinician promptly

  • Chest pain or pressure, breathlessness, sweating or pain spreading to the arm, neck or jaw: call emergency services immediately.
  • Sudden weakness, facial droop, speech difficulty or loss of vision, even if brief: possible stroke or TIA.
  • An LDL-P above 2,000 nmol/L, or LDL-C above 190 mg/dL, at any age, to be evaluated for familial hypercholesterolemia and to arrange family screening.
  • A high LDL-P with diabetes, high blood pressure, smoking, kidney disease or a family history of heart attack before 55 (men) or 65 (women), to discuss formal risk assessment and whether a statin is warranted.
  • An LDL-P that remains above goal despite a good LDL-C on treatment, to review whether therapy or lifestyle should be intensified.
  • Calf pain on walking, cold or discolored feet or slow-healing foot wounds, which suggest peripheral artery disease.

Frequently asked questions

What is a normal LDL particle number?

On the NMR LipoProfile, an LDL-P under 1,000 nmol/L is optimal (about the 20th percentile of US adults), 1,000–1,299 near optimal, 1,300–1,599 borderline high, 1,600–2,000 high and above 2,000 very high. People with established heart disease or diabetes are generally aimed at under 1,000. Ion-mobility and other methods use different numbers, so compare with the range printed on your own report.

Is an LDL-P of 1,500 or 1,800 high?

An LDL-P of 1,500 is borderline high, roughly equivalent to an LDL cholesterol of 150 mg/dL; 1,800 is in the high band (1,600–2,000), equivalent to an LDL-C around 175. Either number means more atherogenic particles than ideal, and what to do about it depends on your other risk factors: age, blood pressure, smoking, diabetes, kidney function and family history. Ask for a 10-year risk estimate rather than reacting to the number alone.

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

LDL-C measures how much cholesterol the LDL particles carry in total (mg/dL); LDL-P counts the particles (nmol/L). They usually move together, but when particles are small and cholesterol-poor, as in insulin resistance, LDL-C can look fine while LDL-P is high, and in the Framingham and MESA studies risk followed the particle count. When they agree, LDL-C is all you need; when triglycerides are high or risk is borderline, LDL-P or apoB gives a more accurate picture.

What is small dense LDL and is it worse?

Small dense LDL particles are LDL that have been stripped of some cholesterol and shrunk, usually because triglycerides are high. They enter the artery wall more easily, stick to it longer and oxidize more readily, so on a per-particle basis they are somewhat more harmful, and a high small LDL-P or small dense LDL cholesterol is a marker of insulin resistance. Once total particle number is known, however, size adds little to risk prediction: a high count of large particles is also dangerous, and lowering the count is the goal.

Should I get an NMR LipoProfile?

It is most useful if you have high triglycerides, low HDL, a large waist, prediabetes or type 2 diabetes, or a family history of early heart disease with a borderline LDL-C, because those are the situations where LDL-C misleads. It is not needed for routine screening, and an apolipoprotein B test (around 20 to 40 US dollars and widely covered) answers the same question. US guidelines mention apoB but not LDL-P, and many insurers do not cover NMR testing.

How do I lower my LDL particle number?

The same measures that lower LDL cholesterol lower LDL-P, with extra emphasis on insulin resistance: lose weight if overweight, reduce refined carbohydrate and sugar-sweetened drinks, replace saturated fat with nuts, seeds, fish and vegetable oils, add 10 g of psyllium or 3 g of oat beta-glucan a day, and build up to the equivalent of 150 or more minutes of brisk activity a week. Statins lower LDL-P by 25 to 45 percent and are recommended when overall risk is high enough. Recheck in 3 to 6 months.

Why is my LDL-P high when my cholesterol is normal?

Because your LDL particles are carrying less cholesterol each, so it takes more of them to produce the same LDL-C. This happens when triglycerides are high and the particles have been remodeled into small, dense forms, which is characteristic of insulin resistance, fatty liver, excess abdominal fat, prediabetes and PCOS. Check the triglyceride, small LDL-P and LP-IR values on your report, and ask for an A1C; the fix is mainly weight, carbohydrate and activity.

Does LDL-P change on a statin?

Yes, but by less than LDL-C. Statins typically lower LDL-C by 30 to 50 percent and LDL-P by 25 to 45 percent, so it is common for LDL-C to reach goal while LDL-P (or apoB) stays above it; in the statin trial meta-analysis, residual risk on treatment tracked non-HDL and apoB more closely than LDL-C. If your LDL-P remains high on treatment, that is a reason to intensify lifestyle measures or discuss adding ezetimibe, not a sign the statin has failed.

References

  1. Cromwell WC, Otvos JD, Keyes MJ, et al.. LDL particle number and risk of future cardiovascular disease in the Framingham Offspring Study: implications for LDL management. Journal of Clinical Lipidology (2007)
  2. Otvos JD, Mora S, Shalaurova I, Greenland P, Mackey RH, Goff DC Jr. Clinical implications of discordance between low-density lipoprotein cholesterol and particle number. Journal of Clinical Lipidology (2011)
  3. Mora S, Szklo M, Otvos JD, et al.. LDL particle subclasses, LDL particle size, and carotid atherosclerosis in the Multi-Ethnic Study of Atherosclerosis (MESA). Atherosclerosis (2007)
  4. Jeyarajah EJ, Cromwell WC, Otvos JD. Lipoprotein particle analysis by nuclear magnetic resonance spectroscopy. Clinics in Laboratory Medicine (2006)
  5. Davidson MH, Ballantyne CM, Jacobson TA, et al.. Clinical utility of inflammatory markers and advanced lipoprotein testing: advice from an expert panel of lipid specialists. Journal of Clinical Lipidology (2011)
  6. Sniderman AD, Thanassoulis G, Glavinovic T, et al.. Apolipoprotein B particles and cardiovascular disease: a narrative review. JAMA Cardiology (2019)
  7. Hoogeveen RC, Gaubatz JW, Sun W, et al.. Small dense low-density lipoprotein-cholesterol concentrations predict risk for coronary heart disease: the Atherosclerosis Risk in Communities (ARIC) study. Arteriosclerosis, Thrombosis, and Vascular Biology (2014)
  8. Grundy SM, Stone NJ, Bailey AL, et al.. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA guideline on the management of blood cholesterol. Circulation (2019)
  9. Kraus WE, Houmard JA, Duscha BD, et al.. Effects of the amount and intensity of exercise on plasma lipoproteins. New England Journal of Medicine (2002)
  10. Krauss RM, Blanche PJ, Rawlings RS, Fernstrom HS, Williams PT. Separate effects of reduced carbohydrate intake and weight loss on atherogenic dyslipidemia. American Journal of Clinical Nutrition (2006)
  11. Jovanovski E, Yashpal S, Komishon A, et al.. Effect of psyllium (Plantago ovata) fiber on LDL cholesterol and alternative lipid targets, non-HDL cholesterol and apolipoprotein B: a systematic review and meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition (2018)
  12. Cholesterol levels. MedlinePlus, US National Library of Medicine (2024)View source

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This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.