Red cell size Mean Corpuscular Volume (MCV)
The average size of your red cells.
Also printed asMCV · Mean Cell Volume
What it measures
The average size of one of your red cells.
The first split in working out any anaemia: small points at iron or thalassaemia, large at B12, folate or alcohol.
Why it matters for how long you stay well
Small cells point at iron or an inherited trait; large ones point at B12, folate or alcohol. Each of those is worth catching early, and each has a different fix.
How it shows up in daily life
You cannot feel cell size, but it is the fastest clue to why you might be feeling tired.
High and low readings
When it reads high
Large red cells point to low B12 or folate, or to alcohol.
When it reads low
Small red cells point to low iron, or to an inherited trait.
What moves it
Daily life
- iron stores
- B12 and folate intake
- alcohol, which enlarges cells
- an inherited small-cell trait, common in India
Medicines known to shift it
- vitamin B12 supplements (lower it when B12 was low)
- iron supplements (raise it when iron was low)
Listed so a result can be read in context. It is not advice to start, stop or change any medicine; that decision belongs with your physician.
Read it with
Markers that move this one, or that this one moves. One number read alone can mislead.
- Ferritin, your iron storeKnown mechanism
Ferritin pushes it up
Short of iron, your body builds smaller red cells rather than fewer of them. So the average cell size drops as your stores run down.
- Red cell sorting ratio, the Mentzer indexObserved association
As this rises, Red cell sorting ratio is calculated from it
The Mentzer index is your red cell size divided by your red cell count. It sorts two kinds of small cells; it does not measure anything new.
- Haemoglobin per cellKnown mechanism
As this rises, Haemoglobin per cell moves with it
Smaller cells carry less pigment each. So cell size and pigment per cell move together, and the second mostly confirms the first.
- Vitamin B12Known mechanism
Vitamin B12 pulls it down
Without enough B12 your body builds oversized red cells. So a low B12 shows up on the blood count as a raised cell size.
- FolateKnown mechanism
Folate pulls it down
A folate shortage causes exactly the same oversized cells as a B12 shortage. That is why both have to be checked before either one is corrected.
Common questions
What does Mean Corpuscular Volume measure?
The average size of one of your red cells. The first split in working out any anaemia: small points at iron or thalassaemia, large at B12, folate or alcohol.
What does a high Red cell size result usually mean?
Large red cells point to low B12 or folate, or to alcohol.
What does a low Red cell size result usually mean?
Small red cells point to low iron, or to an inherited trait.
What is the usual reference range for Red cell size?
A broad adult reference band is 80–100 fL. Labs differ, so read your result against the band printed on your own report.
Educational only, not a diagnosis. A single number means little without your history and the rest of your panel, so discuss your own results with your physician.
Typical adult reference band
- Adults
- 80–100 fL
Labs differ. The band printed on your own report is the one that applies to your result.
Reported in fL
Ageing relevance
5/5
A direct input to a validated biological-age algorithm.
One of the nine blood inputs to the PhenoAge biological-age clock (Levine et al., Aging, 2018).
Worth knowing
Small cells point towards iron or an inherited trait, and large ones towards B12 or folate, so one number sorts two very different problems.
Have a report with this marker on it? Read it in context.
Upload it to Oraia, our health-intelligence tool, for a plain-language read of your markers that a Genoryx doctor can review.
Your biological age is a number you can measure.
Start with the 400+ parameter entry assessment and a 60-minute physician consultation at either Hyderabad clinic. Open seven days, 11 AM to 9 PM.
Book a consultation