MPV: what it is, what it tells you and what high or low means

MPV, or mean platelet volume, shows how big your platelets are on average. Young platelets are bigger. On its own it says little: it is read together with your platelet count.

Why we test it

Platelets are the cell fragments that stop bleeding when a blood vessel is damaged. MPV shows how big they are on average.

Platelets fresh from the marrow are bigger. That is why MPV, read with your platelet count, can give a clue about how your marrow is working.

It needs no extra blood: the machine that runs your blood count works it out from the same sample.

What it tells you, and what it does not

On its own it says little. With a normal platelet count, an MPV outside the limits is usually nothing to worry about.

With low platelets, though, it can give a clue. A high MPV can suggest platelets being used up fast and replaced by young ones; a low MPV, a marrow that makes too few.

But different machines give different values, so it stays a clue: your doctor looks for the cause with other tests.

That is why it is read together with other tests:

• Platelets: Without their count, MPV says little
• Haemoglobin: If it is low along with your platelets, your doctor looks at the marrow
• White blood cells: They show an infection, and whether the marrow works well
• MCV: Very small red cells can shift MPV

Normal MPV levels

There is no normal value that holds for every lab. Each lab prints its own limits next to your result, in fL: femtolitres, a unit for tiny volumes.

The reason is that different machines measure MPV in slightly different ways. Compare your number with the limits on your own report, not with another lab’s.

In the Rosa report you find your MPV together with your platelet count and the rest of your blood count.

If your MPV is high or low

• High MPV: Your platelets are bigger on average. With a normal platelet count, it usually does not matter.
• Low MPV: Your platelets are smaller on average. It matters mostly if your platelets are low too.

High or low MPV: the causes

It almost always needs reading together with your platelet count.

• The lab’s machine: A value just outside the limits can come from how the machine measures, more than from your body.
• Platelets replaced fast: If your body uses up more of them, the marrow releases young, bigger platelets, and MPV goes up.
• Less production in the marrow: More rarely, a low MPV with low platelets points to a marrow that is working less. Your doctor assesses it.

What can skew the result

Three things are worth knowing before you read it.

• Different labs: Different machines give different values. To compare two tests, it is best to have them at the same lab.
• Platelets clumping in the tube: If your report flags them, your doctor has the platelet count repeated, and MPV is read with the new one.
• Very small red cells: If your MCV is low, from low iron or an inherited trait, the machine can read MPV differently.

When to worry

MPV on its own is usually nothing to worry about. Talk to your doctor if:

• Your platelets are outside your report’s limits too.
• Other blood count values are off too, such as haemoglobin or white blood cells.
• You bruise for no reason.
• Tiny red spots appear on your skin for no reason: see a doctor the same day.
• Bleeding will not stop: call 112 or go to the emergency department.

Frequently asked questions

High MPV: should I worry? Usually not, if your platelets are normal. On its own it is not used to make a diagnosis, and a value just above the limit can come from the machine. If your platelets are off too, talk to your doctor.

Low MPV: what does it mean? That your platelets are smaller on average. With a normal platelet count it usually does not matter. If your platelets are low too, your doctor may want to check whether your marrow makes enough.

High MPV and low platelets: what does it mean? It can mean your body is using up platelets fast and the marrow is replacing them with young, bigger ones. It is only a clue: your doctor looks for the cause, starting from your platelet count.

Does a high MPV mean a risk of heart attack or thrombosis? Some studies find slightly bigger platelets in people who have had a thrombosis, but the differences are small. For one person, MPV is not used today to judge that risk: other things matter, such as cholesterol, blood pressure and smoking.

Should I track my MPV over time? Not really. It changes very little in the same person, while different machines give different values: a change between two tests can come from the lab, not from you.

How often should it be checked? For people who feel well there is no fixed rule: Rosa measures it twice a year, with the blood count. If your platelets are out of range, your doctor decides when to check again.

Sources

• Harrison and colleagues, an international study across laboratories on measuring MPV with different instruments. Platelets, 2022. PMID 35473564
• Noris, Melazzini and Balduini, what MPV is really useful for in clinical practice. Platelets, 2016. PMID 27686008
• Walle and colleagues, MPV to tell immune thrombocytopenia from low platelet production: a systematic review and meta-analysis. PLoS One, 2023. PMID 38033118
• Coşkun and colleagues, how much blood count values change in the same person, week by week, and between people. Clinical Chemistry and Laboratory Medicine, 2018. PMID 29605821