Myeloperoxidase (MPO) Test: The Blood Test That Reads Inflammation Inside Your Artery Walls

When you order the lab tests presented on this page, NutriScape, LLC receives affiliate fees so that our dietitians can continue to create great content.

Thank you for your support!

Your cholesterol panel can come back clean while plaque inside an artery wall sits quietly inflamed and unstable, and a cholesterol test does not measure that. Myeloperoxidase, or MPO, is an enzyme your white blood cells release into inflamed tissue, and its level in the blood reads that inflammation. On the heart-risk picture, MPO fills in something cholesterol numbers leave out: how active the inflammation in your blood vessels is right now.

It is a single blood draw with no fasting required. The one thing that matters for timing is that you feel well when you give the sample, because a cold, a recent injury, or a flare of an ongoing condition can raise MPO for reasons that have nothing to do with your heart.

What MPO Tells You

Myeloperoxidase is an enzyme that neutrophils and monocytes, two kinds of white blood cell, carry and release when they meet inflammation. Releasing it is part of how those cells attack bacteria. The same chemistry that helps them do that also produces reactive oxidants, and when the release happens inside the wall of an artery, those oxidants damage the vessel from within.

How It Acts on the Artery Wall

Inside an artery wall, MPO oxidizes LDL cholesterol and uses up nitric oxide, the molecule that keeps the vessel lining relaxed and healthy. Both effects push a stable plaque toward an unstable one, thinning the fibrous cap that holds the plaque together.

A plaque with a thin, inflamed cap is more likely to crack, and a crack can trigger a clot, which is what causes most heart attacks and many strokes. So MPO does not simply mark inflammation, it takes part in the process that turns quiet plaque into a dangerous one.

Why a Higher Number Matters

Because MPO sits in that process, a higher level points to more of the active, vessel-wall inflammation that a cholesterol number alone would miss. In people evaluated for chest pain, a higher MPO tracked with a greater chance of a heart attack in the months that followed, even when the standard heart-damage blood test still looked normal (PMID: 14573731).

That is the piece MPO adds: a read on how inflamed and unstable the process is, not simply how much cholesterol is present.

Who Should Consider This Test

MPO earns its place when the question goes past how much cholesterol you carry to how active the inflammation around it is, especially when the usual numbers sit in a gray zone.

• Normal or borderline cholesterol paired with other reasons for concern, such as a family history of early heart disease or high blood pressure
• Signs of metabolic strain, including a larger waist, prediabetes, insulin resistance, or fatty liver, which tend to keep vascular inflammation higher
• A wish to see whether the everyday work of lowering inflammation is moving the number over months, using a before-and-after result
• A pairing with hs-CRP or Lp-PLA2 when you want more than one read on inflammation before a decision
• Follow-up once chest pain or a cardiac event has been evaluated, where the marker adds to the picture

The through-line in these situations is a decision that is not yet settled. In people with acute coronary syndromes, a higher MPO flagged those at greater risk even when other markers looked reassuring, which is part of why it helps most exactly when the picture is unclear (PMID: 12952835).

Normal Range vs. Optimal Range

MPO is reported in picomoles per liter of blood (pmol/L). Access Labcorp Draw sorts the result into cardiovascular risk bands, and the rule is that a lower number points to less vascular inflammation and lower risk.

Why Lower Is Better

The bands sort people into risk groups, but they do not draw a clean line between safe and unsafe. Lower is better across the whole range, so a result well under 470 is the target, and a number in the moderate band is a prompt to find what is driving the inflammation, not a reason to relax.

A level a lab calls acceptable is not the same as the best level for your arteries.

What Else Can Raise the Number

Two things can lift MPO for reasons unrelated to your heart. An active infection, an injury, or a flare of an inflammatory condition pushes it up, so a high reading taken while you are unwell is worth repeating once you recover. Sample handling matters too: blood that is not separated and chilled promptly can read falsely high, so a surprising result is worth confirming with a second test.

What Your Result Points Toward Next

A raised MPO that lines up with the everyday drivers of vascular inflammation, a larger waist, higher blood sugar, a fatty liver, or smoking, points toward the changes that lower it over time. Fiber, omega-3 fats from fish, steadier blood sugar, more movement, better sleep, and stopping smoking all help.

A registered dietitian nutritionist can build that into a plan around heart health that fits your life, and you can connect with one at nourish.com.

A raised MPO in someone who is being evaluated for chest pain, or who has had a recent cardiac event, points somewhere more immediate. There it is one input for the physician or cardiologist managing that care, and it belongs in that conversation rather than a number you act on by yourself.

Order This Lab Without A Prescription

Related Tests and When Each Makes Sense

MPO answers one question: how active the inflammation inside your artery walls is. It does not count the cholesterol particles being deposited or measure inflammation elsewhere in the body. These tests fill in the parts it leaves open.

The hs-CRP test reads low-grade inflammation from anywhere in the body, not the artery wall in particular. It pairs well with MPO when you want both a whole-body inflammation number and a vessel-specific one.

The Lp-PLA2 test reads an enzyme tied specifically to inflammation inside artery walls, much like MPO. The two are often read together to confirm that the inflammation is landing in your blood vessels rather than somewhere else.

The Apo B test counts the cholesterol-carrying particles that lodge in artery walls and start plaque. Inflammation and particle count are two separate halves of heart risk, so measuring both tells you whether the problem is what is being deposited, how inflamed the process is, or both.

The CVD and Diabetes Prevention Comprehensive panel gathers inflammation markers, cholesterol particles, and blood sugar measures into one draw. It is the better pick for someone who wants the full cardiovascular and metabolic picture at once rather than the single inflammation number.

If active vascular inflammation is what you came to measure, you can order the MPO test above.

The information provided in this article is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. Functional medical tests and nutrition-related labs should be used as tools to support health and wellness under the guidance of a qualified healthcare provider. Results from these tests should not replace professional medical advice or be interpreted without consulting a licensed practitioner familiar with your health history and needs. Always consult your doctor or dietitian before making changes to your diet, supplements, or health management plan.