MPO is an enzyme released by neutrophils (a type of white blood cell) during immune activation. In the vasculature, MPO both fights pathogens and damages artery walls, making it particularly relevant to cardiovascular inflammation.
Elevated MPO is a specific marker of vascular inflammation and oxidative stress within the arteries themselves. It indicates active arterial injury, not just generalized inflammation. It's particularly useful for assessing cardiovascular risk in people with normal cholesterol but active vascular inflammation. MPO is increasingly measured in advanced cardiovascular panels (Cleveland HeartLab's lineup includes it) and correlates with future cardiovascular events independent of LDL-C.
Optimal Myeloperoxidase: 0-400 pmol/L.
Typically re-tested every 12 weeks.
This article is educational and is not medical advice.
Myeloperoxidase, usually shortened to MPO, is an enzyme stored inside the granules of neutrophils and some monocytes, released when those cells are activated, and measurable in blood as a marker of inflammatory and oxidative activity 1.
Neutrophils are the immune system's first responders. When one of them encounters bacteria, it degranulates and releases its enzyme payload. MPO then takes hydrogen peroxide and chloride, both abundant in tissue, and combines them into hypochlorous acid, the same reactive chlorine chemistry that makes household bleach effective. It is a blunt and very fast way to kill microbes, and reviews describe it as a central part of innate immune defence 10.
The problem is that this chemistry does not distinguish between a bacterium and the tissue next to it. When neutrophil activation is brief, the collateral damage is small and repaired. When low-grade activation continues for months or years, the same oxidants modify the body's own molecules. They oxidise lipoproteins, they chlorinate tyrosine residues on proteins (the chlorinated product 3-chlorotyrosine serves as a chemical footprint of MPO activity), and they consume nitric oxide, the molecule blood vessels rely on to relax and stay flexible. Reviews describe MPO as a link between inflammation, oxidative stress and vascular disease rather than as a bystander 2, 3.
One point of confusion is worth clearing up early. A separate test, the myeloperoxidase antibody test (written variously as MPO antibody, MPO Ab, MPO antibodies test or MPO-ANCA), does not measure the enzyme at all. It looks for antibodies directed against MPO, and clinicians order it when evaluating certain forms of small vessel inflammation. The enzyme result and the antibody result answer completely different questions and are not interchangeable, so check which one your report actually lists before trying to interpret it.
It matters because it reports on inflammatory activity inside the blood vessel wall rather than on the amount of cholesterol passing through it, which makes it a different kind of signal from a standard lipid panel.
Atherosclerosis is not simply a plumbing problem. Plaque forms when lipoproteins lodge in the artery wall, become oxidised, and draw in immune cells that never fully clear the mess. MPO sits at several steps of that process at once. Research suggests it promotes lipoprotein oxidation, reduces nitric oxide availability, and contributes to the thinning of the fibrous cap that keeps a plaque stable 2, 4. That last point is why the marker attracted interest in the first place. A stable plaque that narrows an artery behaves very differently from an inflamed one that is prone to rupture, and conventional lipid numbers say little about which is which.
Studies in people with acute coronary syndromes have examined MPO activity in relation to long-term outcomes, and findings from the ERICO cohort indicate that the marker carries prognostic information in that setting 5. Work in chronic kidney disease points in a similar direction. In the Chronic Renal Insufficiency Cohort study, MPO was examined in relation to kidney disease progression, cardiovascular events and mortality 6, and separate research has linked MPO levels and the 3-chlorotyrosine footprint to kidney disease severity and to coexisting coronary artery disease 7.
There is a metabolic thread too. In people with ischaemic heart disease, research has examined MPO alongside paraoxonase-1, an enzyme carried on HDL particles that helps limit lipid oxidation, and reported associations with type 2 diabetes 8. Taken together, MPO appears to track the oxidative, inflammatory side of cardiometabolic disease.
All of this is association, measured across groups of people. It describes risk patterns in populations, not a verdict about any one person's arteries.
Most laboratories report myeloperoxidase as a concentration in pmol/L, and a typical reference range sits below roughly 470 pmol/L.
| Reference | Myeloperoxidase level |
|---|---|
| Typical lab reference range | 0 to 470 pmol/L |
| FitScript optimal range | 0 to 400 pmol/L |
Reference ranges vary by laboratory, assay, age and sex, so always read your result against the range printed on your own report. FitScript's optimal range is an optimisation target, not a diagnostic cut-off, and a value sitting above it is not a diagnosis of anything.
Two practical notes. First, units differ between laboratories, and some report in ng/mL rather than pmol/L, so comparing two results from different labs without checking units will mislead you. Second, assays for this marker are not perfectly standardised, which is another reason to track your own trend on a consistent assay rather than to compare your number against a figure quoted in an article.
An elevated result indicates that neutrophils have been active and releasing their enzyme payload, and it is worth discussing with a clinician alongside the rest of your bloodwork and your history.
Symptoms people report. Usually none. This is a silent marker, and a raised value is often found on a panel in someone who feels entirely well. When symptoms are present, they tend to belong to whatever is driving the inflammation rather than to the enzyme itself: tiredness that does not resolve with sleep, aching joints, bleeding or tender gums, lingering symptoms after an infection, or chest discomfort and breathlessness on exertion. Chest discomfort, pressure, breathlessness or pain spreading to the jaw or arm is worth urgent medical attention regardless of what any lab value says.
Common causes. Any active infection raises neutrophil activity, and research has described MPO as a circulating marker of inflammation that rises in the setting of tooth infection, which is a reminder that oral health is not separate from vascular health 9. Smoking and vaping load the airways with oxidative stress. Autoimmune and inflammatory conditions raise it. Reduced kidney function is associated with higher levels 7. Recent intense exercise, a recent viral illness, and certain sample handling issues can all nudge a value upward for reasons that have nothing to do with your arteries.
Long-term health impact. Across cohort studies, higher MPO has been associated with cardiovascular events, with kidney disease progression and with mortality 5, 6. Those associations are strongest in people who already have established disease, and a single elevated value in an otherwise healthy person is best read as a prompt to look harder, not as a prediction.
The sensible next step. A single high value is a question, not an answer. The usual approach is to look for an obvious inflammatory source first (dental infection, recent illness, a flare of a known condition), address what is addressable with your clinician, and repeat the test once things have settled. Never ignore a result that sits outside the standard range, and if it comes with symptoms, raise it with a clinician promptly.
A low or undetectable result is generally unremarkable and is usually read as a sign of low circulating neutrophil activation rather than as a problem.
Symptoms people report. Typically none at all. A low value is the expected finding in a person without active inflammation.
Common causes. The ordinary explanation is simply an absence of active inflammatory disease. There is also an inherited condition, myeloperoxidase deficiency, in which neutrophils are produced with little or no functional enzyme. It is recognised as one of the more common inherited neutrophil abnormalities and most people who carry it never notice it, because other infection-fighting mechanisms compensate. Laboratories regard it as largely silent, although reports describe an increased susceptibility to fungal infection, particularly candida, in a minority and mainly in people with diabetes. Assay variation and sample handling can also produce an artificially low figure.
Long-term health impact. Low MPO is generally the direction most people would prefer. The important caveat is that a low value does not clear you of cardiovascular risk. It reports on one inflammatory pathway. Lipoprotein burden, blood pressure, blood sugar and family history all sit outside what this marker can see, which is why it is read as part of a panel and not on its own.
Several things unrelated to long-term vascular health can move this number, which is why context around the blood draw matters as much as the number itself.
Testing conditions. Sample type and handling matter more for this marker than for most. Delays before the sample is processed, haemolysis, and differences between serum and plasma tubes can all shift the result. Where possible, use the same laboratory each time so that your trend means something.
Recent physiology. An acute infection of any kind, including a dental one, raises neutrophil activity 9. Strenuous or unaccustomed exercise may transiently activate neutrophils, so a test taken the morning after a hard session may not reflect your usual state. Most people get a cleaner reading by testing on a normal week rather than during illness or immediately after a race.
Habits. Smoking and vaping are the most consistent modifiable contributors to oxidative load. MPO has been described as a circulating marker of inflammation and tooth infection 9. Dietary patterns rich in unprocessed plants, oily fish and olive oil may support lower markers of oxidative stress generally, although any link is broad and uncertain rather than a specific effect on MPO.
Medications. Kidney function influences the result, so anything that changes it will show up here over time. No medication should be started, stopped or adjusted on the basis of this marker. A licensed provider evaluates whether any prescription therapy is appropriate for you, and no article can make that call. This page gives no doses, amounts or schedules for any therapy, by design.
FitScript does not currently include myeloperoxidase in a lab panel, so this is one marker a member will not see appear automatically among the 150+ biomarkers tested per year.
If you already have a result from another laboratory, you can upload your labs so that Atlas, the AI health advisor, can read it in context with the rest of your bloodwork rather than in isolation. That context is the point. An MPO value read next to your lipoprotein burden, kidney function, glucose handling and general inflammatory markers tells a far more useful story than the same number read on its own, and it feeds into your FitScript, the personalised output Atlas writes from your biology.
Where a result raises questions that point toward medication or any other prescription option, a licensed provider reviews your full picture and decides whether it is appropriate. Discuss your results and any treatment decisions with a clinician or licensed provider before acting on them.
This enzyme describes one slice of inflammation, so it is most informative when read with markers that cover the other slices.
Myeloperoxidase is an enzyme your neutrophils use as a chemical weapon, and the blood test tells you how much of that weapon has been leaking into circulation. Higher levels are associated with oxidative stress, inflamed arterial plaque, kidney disease progression and cardiometabolic risk, but the result is a signal about activity, not a diagnosis. Read it as a trend, in context, with the markers above, and take any value outside the standard range to a clinician rather than to a search engine.
It measures how much of the neutrophil enzyme myeloperoxidase is circulating in blood, which reflects inflammatory and oxidative activity. Higher levels are associated with inflamed arterial plaque, kidney disease progression and cardiometabolic risk. It is used as one input alongside lipid, inflammatory and kidney markers, never as a standalone diagnosis.
No. The enzyme test measures myeloperoxidase itself. The MPO antibody test, also written MPO Ab or MPO-ANCA, looks for antibodies directed against the enzyme and is ordered when a clinician is evaluating certain forms of small vessel inflammation. The two answer different questions, so check which one appears on your report.
A typical laboratory reference range sits at 0 to 470 pmol/L, and FitScript's optimal range is 0 to 400 pmol/L. Optimal ranges are optimisation targets, not diagnostic cut-offs. Ranges vary by laboratory, assay, age and sex, and some labs report in ng/mL instead, so read your number against the range printed on your own report.
It suggests neutrophils have been active and releasing the enzyme. Common contributors include active infection, dental disease, smoking, autoimmune inflammation, reduced kidney function and insulin resistance. A single elevated value is a prompt to look for a source and retest once things settle, and it is worth discussing with a clinician alongside your other markers.
Yes. Myeloperoxidase is a circulating marker of inflammation that can rise in the setting of tooth infection. Gum disease and dental abscesses are an often overlooked inflammatory source, which is one reason a raised value is usually investigated for an obvious cause before anything is read into it.
Fasting is not generally required for this marker, but it is often drawn with a lipid panel that may carry its own instructions, so follow the guidance your laboratory provides. It is also sensible to avoid testing during an acute illness or immediately after very hard exercise, since both can transiently raise the result.
Not on its own. A low value usually reflects little active neutrophil-driven inflammation, which is the preferable direction, but it says nothing about lipoprotein particle burden, blood pressure, blood sugar or family history. Cardiovascular risk is assessed from the full picture, which is why this marker is read as part of a panel.
C-Reactive Protein for general inflammation, Oxidized LDL for modified lipoprotein particles, Apolipoprotein B for atherogenic particle count, Fibrinogen Activity for the inflammation and clotting overlap, Homocysteine for endothelial stress, and ESR as a slower-moving inflammatory measure. Together they separate transient inflammation from a persistent vascular pattern.
FitScript does not currently include this marker in a lab panel. If you already have a result from another laboratory, you can upload your labs so Atlas can read it in context with the rest of your bloodwork. Any question about prescription options is reviewed by a licensed provider, who decides what is appropriate.