A high MCV means your red blood cells are on average larger than normal, usually above 100 fl. The medical term is macrocytosis. Of every value in your blood count, this is the one you can least wave away with "I trained hard yesterday", because training barely changes your MCV.
That is exactly what makes it valuable.
Where your haemoglobin and your white cells swing around with your training schedule, your MCV sits there fairly unmoved. If it is high, there is usually another reason. And that reason is worth chasing.
What is a normal MCV value?
Most Dutch labs use roughly 80 to 100 fl (femtolitres) as the reference. Below 80 your cells are called microcytic, above 100 macrocytic. MCV stands for mean corpuscular volume, and like MCH it is a calculation: your haematocrit divided by your red blood cell count.
Always read the range on your own result, because labs differ.
And do not read the MCV alone. It only becomes informative next to your haemoglobin and your MCH.
What causes a high MCV?
In Dutch general practice the two best known causes are alcohol and a deficiency of vitamin B12 or folate. Research among Dutch primary care patients with macrocytic anaemia found exactly that pattern: a shortage of B12 or folate and excessive alcohol use are among the most common explanations (PMID 27542607).
Alcohol enlarges your red cells even without a vitamin deficiency. It is a direct effect on your bone marrow, and one of the earliest traces drinking leaves in your blood.
| Possible cause | What you often see alongside | What you want measured with it |
|---|---|---|
| Regular alcohol use | MCV mildly to moderately raised, sometimes raised gamma-GT | Liver values |
| Vitamin B12 deficiency | MCV high, sometimes tingling or fatigue | Vitamin B12 |
| Folate deficiency | A picture similar to B12 | Folate |
| Underactive thyroid | MCV mildly raised, tiredness, cold intolerance | TSH |
| Liver disease | Raised liver values | ALT, AST, gamma-GT |
| Certain medicines | An isolated raised MCV | Bring your medication list |
A raised MCV without anaemia is common, and not automatically alarming. Research among middle-aged and older adults found that macrocytosis is by no means always linked to a vitamin deficiency (PMID 24244281).
Why is a high MCV in athletes a reason to look further?
Because the usual sporting explanation does not apply here. With your haemoglobin, haematocrit and white cells you can often attribute a deviation to dilution or to yesterday session. With your MCV you cannot: it barely moves with your training schedule.
That makes a raised MCV in an athlete relatively more informative than in anyone else. There is less noise to cross out.
Take a strength athlete with an MCV of 103 fl, a normal haemoglobin and otherwise fine values. There is no training explanation. There are, however, three glasses of wine an evening, or a plant-based diet without B12 supplementation. Those are the questions that belong on the table.
I watch athletes panic over a haemoglobin that dropped through dilution, and look straight past an MCV of 104. That is exactly the wrong order.
Can a high MCV be harmful?
The MCV itself is not a disease; it is a clue. Large red cells usually do their job perfectly well, and many people with a mildly raised MCV notice nothing at all. What sits underneath it may deserve treatment, which is why a raised value is a reason to look further rather than to ignore.
A B12 deficiency that persists for a long time can cause nerve symptoms, for instance. That is not something to sit out.
The NHG guideline on anaemia describes macrocytosis as a finding that calls for an explanation. Not as a diagnosis, but not as noise either.
When should you discuss a raised MCV with your GP?
Almost always, and certainly if it stays above 100 fl on a repeat measurement. This is the value in your blood count I would take least lightly. Especially combined with fatigue, tingling in hands or feet, or if you drink regularly.
Take your whole blood count with you, and your medication list. An isolated raised MCV calls for a different route than a raised MCV with anaemia alongside it (PMID 17619679).
And be honest about your drinking. Your MCV has already been honest about it.
Where do you start?
Have your MCV repeated and your vitamin B12 measured with it. Those two numbers together almost always give direction. Our complete blood count test gives you MCV, MCH and the rest of the red series, with an assessment by a BIG-registered doctor.
How to read all the values together is in complete blood count explained. What your MCH says about your iron is in the MCH value. What alcohol does to your blood values and your recovery is in alcohol and your blood values, and the B12 side is in vitamin B12 and energy.
References
- Croonen EA, et al. Prevalence of potential underlying aetiology of macrocytic anaemia in Dutch general practice. BMC Family Practice. 2016. PMID 27542607.
- Haematinic deficiency and macrocytosis in middle-aged and older adults. PLoS One. 2013. PMID 24244281.
- Macrocytosis, an Australian general practice perspective. Australian Family Physician. 2007. PMID 17619679.
- NHG. NHG guideline on anaemia. Accessed 2026.
- RIVM. Blood testing and reference values. Accessed 2026.
Disclaimer
Every blood test result includes a professional assessment by a BIG-registered doctor. This article gives general information and is not a substitute for medical advice. For treatment decisions, discuss your results with your GP.
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Enhanced Health
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