A patient seated in the chair before a blood draw
In person

Lipoprotein Fractionation (Ion Mobility)

The number and size of your cholesterol particles, from one draw.

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  • 2,000+ lab locations. Find one near you
  • Nothing due at the lab. FSA / HSA accepted
  • Ordered by a licensed clinician

At a glance

Collection
Blood draw
A standard blood draw at the lab.
Preparation
Fasting preferred
Fast 9 to 12 hours. Water is fine.
Results
2 to 4 days
Typical turnaround after your visit.
Where
2,000+ lab locations
Nationwide, with nothing due at the lab.

About this test

Cholesterol travels in particles called lipoproteins. This test sorts them by size and counts them, reporting LDL particle number, small and medium LDL, large HDL, and your LDL size pattern. It reports particle details that a standard cholesterol test does not include. Fasting for 9 to 12 hours is preferred.

For adults 18 and older. Test availability varies by lab location.

Who should take this test?

This test is for adults who want more detail than a standard cholesterol check, often with a family history of early heart disease or borderline cholesterol results.

Ask about this test

Not sure this is the right test?

AI-generated. For information only, not medical advice. Call 911 for an emergency.

What does this test measure?

Your results show how many LDL particles you have and how they are spread across sizes, which can help a healthcare provider add detail to your heart risk.

LDL particle number
This measures how many LDL particles are in your blood, rather than how much cholesterol they carry. Two people with the same LDL cholesterol can have different numbers of particles. The lab measures particle number and size using a method called ion mobility.
Why it’s measured: Counts LDL particles, which can differ from LDL cholesterol.
LDL small
LDL particles come in different sizes. This result reports the concentration of the smaller, denser LDL particles. Research has linked a higher share of small LDL particles with heart risk. It is one part of the particle report and is read with your other lipid results.
Why it’s measured: Reports the smaller LDL particles, read with your other lipid results.
LDL medium
This result reports the concentration of medium-sized LDL particles. Together with the small LDL result and total particle number, it shows how your LDL particles are distributed by size. A provider reads it as part of the particle report rather than on its own.
Why it’s measured: Shows part of how your LDL particles are distributed by size.
HDL large
HDL particles also come in different sizes. This result reports the concentration of the larger HDL particles. It adds detail to your standard HDL cholesterol result, and it is read as one part of the particle report alongside the LDL particle results.
Why it’s measured: Adds detail on HDL particle size to your standard HDL cholesterol result.
LDL pattern
Based on the size of your LDL particles, the lab assigns a pattern: one where larger particles are more common, one where smaller particles are more common, or one in between. It is a summary of the size results, read with particle number and your other lipids.
Why it’s measured: Summarizes whether larger or smaller LDL particles are more common.
LDL peak size
LDL peak size is the most common size of the LDL particles in your sample. It is reported in very small units and used to set your LDL pattern. On its own it adds limited information, and a provider reads it together with the rest of the particle report.
Why it’s measured: The most common LDL particle size, used to set your LDL pattern.

How it works

  1. Step 1

    Order online

    Check out here. A licensed clinician in your state reviews your order and sends it to the lab.

  2. Step 2

    Visit a lab

    Bring a photo ID to any of 2,000+ lab locations. Fast 9 to 12 hours. Water is fine. Nothing is due at the lab.

  3. Step 3

    Get your results

    Results post to your account, usually in 2 to 4 days, each number next to the lab’s reference range.

Find a lab near you

Choose from 2,000+ lab locations nationwide. Your order works at any of them.

What your results tell you

Each measure is reported as a particle count or a size and compared with the lab’s reference ranges. LDL pattern is reported as a type.

  • Each marker next to the lab’s reference range
  • Explained in plain language
  • A licensed clinician reviews your order and, if appropriate, orders the test.
  • A lab report you can download and share

Particle results add detail to, but do not replace, your other heart risk factors. Review them with a healthcare provider.

Clinical-grade testing, from the comfort of home.

From the lab to your report, every step of our process meets the gold standard in medical testing.

  • CLIA-certified labs

    Every lab we partner with is certified under the Clinical Laboratory Improvement Amendments, meeting both state and federal standards with regular independent inspections.

  • We protect your health data

    We protect your health data with encryption and do not sell it. Some results must be reported to public health authorities by law. See our Privacy Notice.

  • Rigorous quality assurance

    All partner labs run regular internal quality checks, participate in proficiency testing, and comply with federal and state lab regulations.

  • Clinician-reviewed reports

    Results are reviewed by an independent, licensed clinician.

Questions

Common questions.

Anything else, our care team answers by phone, text, or email.

LDL cholesterol tells you how much cholesterol is carried in LDL particles. Particle number tells you how many particles carry it, and size tells you whether they tend to be smaller and denser or larger.

Two people with the same LDL cholesterol can have different particle numbers. Smaller LDL particles have been linked with a higher risk of early heart disease.

LDL pattern sums up whether your LDL particles are mostly larger or mostly smaller. Your report also shows the peak size, which is the size that appears most often in your sample. A healthcare provider reads these together with the particle counts.

Fasting for 9 to 12 hours is preferred, and water is fine. The lab accepts a sample taken without fasting, but fasting keeps results easier to compare over time and with any other cholesterol tests drawn at the same visit.

If you take insulin or other diabetes medicines, ask your prescriber how to fast safely before your visit.

Particle testing does not diagnose heart disease or show whether arteries are narrowed. It adds detail to standard cholesterol results rather than replacing them, and it is read with blood pressure, blood sugar, smoking, and family history. A healthcare provider can explain whether it changes anything for you.

Lab tests are informational and don’t diagnose conditions on their own. Available to adults 18 and older; test availability varies by lab location. A licensed clinician reviews your order and, if appropriate, orders the test. All testing is performed at CLIA-certified laboratories. Not for emergencies: if you think you may be having a medical emergency, call 911.