LDL Particle Size
The typical width of your LDL particles. Small LDL goes with high triglycerides and insulin resistance, but size adds little once your particle count is known.
AI-verified against cited sources. Awaiting expert reviewLOINC 17782-4
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What it is
LDL particles vary in size. This test reports the typical diameter of your LDL particles, in nanometers (nm) on NMR reports or in angstroms (Å) on Quest's ion mobility report. One nanometer equals 10 angstroms. Larger LDL is called Pattern A, and smaller LDL is called Pattern B. Smaller particles carry less cholesterol each, so a person with small LDL can have many particles even when their LDL cholesterol looks fine.
Why it matters
Smaller LDL tends to go along with high triglycerides, low HDL cholesterol and insulin resistance. For years, small LDL was seen as more harmful than large LDL. More recent analyses, such as those cited in a 2011 MESA-based paper, found that small LDL size is linked to heart risk independently of LDL cholesterol, but not independently of LDL particle number. Labcorp's own report says size and small LDL particle count are linked to heart risk but not after LDL particle number is taken into account. For that reason, many clinicians look at LDL-P or apoB rather than size. A 2026 Circulation review says current ACC/AHA guidance recommends against NMR particle testing beyond a standard lipid panel, apoB and Lp(a).
If it’s low
Smaller LDL (Pattern B) goes with high triglycerides, low HDL cholesterol, insulin resistance and extra weight. It is common, and it is not a diagnosis. Because smaller particles carry less cholesterol, your LDL cholesterol can understate how many LDL particles you have, so your clinician may want to look at LDL-P, apoB or non-HDL cholesterol.
Common causes
- High triglycerides
- Low HDL cholesterol
- Insulin resistance, prediabetes or type 2 diabetes
- Extra body weight, especially around the middle
- Little physical activity
What can help
- Habits that lower triglycerides and improve insulin sensitivity: regular activity, a healthy weight, less added sugar and refined carbohydrate, and limited alcohol
- Ask your clinician whether LDL-P, apoB or non-HDL cholesterol would help follow your risk
- Ask whether a blood sugar test such as fasting glucose or A1c is worth checking
If it’s high
Larger LDL is the pattern labs call Pattern A, and it is generally seen as the lower-risk direction. It usually goes with lower triglycerides and better insulin sensitivity. A larger size is not a concern, but it does not tell you whether your LDL cholesterol or particle count is low.
Common causes
- Lower triglycerides
- Good insulin sensitivity
- Higher HDL cholesterol
What can help
- A result in the larger range usually needs no action
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: 20.6 and above nm. Source: Labcorp.
- Adults (this one applies)20.6 and above nm
Source: Labcorp
Labcorp NMR LDL size pattern (Pattern A large, Pattern B small)
- Pattern B (smaller LDL)below 20.6 nm
- Pattern A (larger LDL)20.6 and above nm
What can affect your result
- Method and unit: NMR (Labcorp) reports nm, and ion mobility (Quest) reports Å, with different size definitions and cutoffs
- Triglycerides, insulin resistance, diabetes and body weight
- Fasting: Labcorp asks for 8 hours, and Quest says fasting is preferred but not required
- Physical activity and diet
- Labcorp asks for an 8-hour fast for the NMR LipoProfile. Quest's ion mobility test says fasting is preferred but not required.
- NMR reports size in nanometers (nm) and ion mobility in angstroms (Å). One nm equals 10 Å, but the two methods measure size differently, so a converted number is not a like-for-like result.
- Labcorp rejects samples that are grossly hemolyzed, contaminated with red cells, or held too long at room temperature, and Quest rejects grossly hemolyzed or lipemic ion mobility samples.
Weeks to months. Size follows triglycerides, body weight and insulin sensitivity.
When to talk to a clinician
A smaller LDL size is not an emergency value. Bring it to your next routine visit with your LDL cholesterol, triglycerides and blood sugar results, especially if you have diabetes risk factors or a family history of early heart disease. 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
- Does my LDL size change anything about my care, or are my LDL cholesterol and apoB enough?
- Could high triglycerides or insulin resistance explain a small LDL size?
- Would LDL-P, apoB or non-HDL cholesterol give us a better picture than LDL size?
Questions people ask
What are Pattern A and Pattern B?
Pattern A means mostly larger LDL particles, and Pattern B means mostly smaller ones. On Labcorp's NMR report, Pattern A runs from about 20.6 to 23.0 nm and Pattern B from 19.0 to 20.5 nm.
Why is my LDL size in angstroms (Å)?
Quest's ion mobility report uses angstroms, and NMR reports use nanometers. One nanometer equals 10 angstroms, so 220 Å is 22.0 nm. The two methods measure size differently, though, so don't compare a number from one method with a range from the other.
Is a small LDL size a problem?
Small LDL is common and is not a diagnosis. It often comes with high triglycerides, low HDL cholesterol and insulin resistance. Its link to heart risk is mostly explained by LDL particle number, so your clinician may focus on LDL-P, apoB or non-HDL cholesterol instead.
Show the science and sources
Units
- 1 nm = 1 nm
- 1 nm = 10 Å
Open the LDL Size unit converter
For clinicians and researchers
LDL size is the weighted-average (NMR) or peak (ion mobility) LDL particle diameter. Labcorp's NMR LipoProfile reports mean LDL size in nm (LOINC 17782-4, an 'entitic length'), and Quest's ion mobility report gives LDL peak diameter in angstroms plus an A or B pattern. On Labcorp's standard report, Pattern A (large) spans about 20.6-23.0 nm and Pattern B (small) 19.0-20.5 nm, with a reference of above 20.5 nm. Its report with insulin-resistance markers prints 20.8 nm or more, the median of its reference group (25th and 75th percentiles 20.4 and 21.2 nm), and LDL size is one of six LP-IR inputs (weight 6 of 100 in the original algorithm). A 2011 MESA-based paper notes that small LDL size is associated with atherosclerotic risk independently of LDL-C but not of LDL-P, and that recent analyses (including MESA and the Women's Health Study) do not support the belief that small LDL particles are inherently more harmful. In the JUPITER placebo arm, ion mobility LDL peak diameter (median 220 Å) was inversely associated with first CVD events (HR 0.84 per SD, 95% CI 0.73-0.96), but that association was no longer significant when LDL-C, HDL-C and triglycerides were added to the model. Quest states that LDL pattern A is classed as optimal and pattern B as high risk in its reports, based on population studies, and that the atherogenic profile also includes low HDL-C and high triglycerides. 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 17782-4 (primary). Specimen: serum-or-plasma.
Sources
- NMR LipoProfile+Lipids+Graph, sample patient report (test 123810), Labcorp (2024)
- NMR LipoProfile+IR+Graph, sample patient report (test 123497), Labcorp (2024)
- NMR LipoProfile With Lipids (With Graph) (test 123810), Labcorp
- Cardio IQ Lipoprotein Fractionation Ion Mobility: clinical education FAQ, Quest Diagnostics
- Cardio IQ Lipoprotein Fractionation, Ion Mobility (test 91604), Quest Diagnostics
- Clinical implications of discordance between low-density lipoprotein cholesterol and particle number, Journal of Clinical Lipidology (2011)
- 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)
- Lipoprotein insulin resistance index: a lipoprotein particle-derived measure of insulin resistance, Metabolic Syndrome and Related Disorders (2014)
- Lipid Profile Testing and Interpretation (summarizes the 2026 ACC/AHA Dyslipidemia Guideline), Circulation (Nguyen, Ahmad, Navar) (2026)
- 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.