MCV value: what does it say about your blood?

Your lab report is full of abbreviations, but MCV is one I always pause on. In a single number it tells you how big your red blood cells are on average. Not how many you have, but whether they are the right size. And that size often points your doctor straight towards the cause of anaemia or fatigue.

My stance up front: an abnormal MCV is not a diagnosis, but a signpost. The nice thing is that the direction in which the cells deviate (too small or too large) often already reveals where the follow-up test should start. That saves guesswork.

What exactly does MCV measure?

MCV stands for mean corpuscular volume, the average volume of a red blood cell, expressed in femtolitres (fL). Think of it as the average shoe size of your red blood cells. Together with your haemoglobin and the number of erythrocytes, MCV shows whether your cells are normal, too small or too large. It is part of a standard complete blood count.

What is the normal value for MCV?

In adults the MCV usually lies between 80 and 100 fL. Within that range your red blood cells are normal in size (normocytic). The exact limits vary slightly per laboratory.

• 80 to 100 fL: normal (normocytic).
• Below 80 fL: microcytic, red blood cells too small.
• Above 100 fL: macrocytic, red blood cells too large.

MCV as a signpost: which direction points to what?

The real power of MCV lies in combining it with other values. The table below is your decision aid: per pattern you see what it classically fits and which follow-up test is logical. It remains a line of reasoning, not a diagnosis.

What does a low MCV (microcytic) mean?

A low MCV means your red blood cells are smaller than normal. That often points to a problem making haemoglobin. Iron deficiency is by far the most common cause. Other possibilities a doctor may consider are chronic inflammation, thalassaemia (a hereditary condition) and, more rarely, lead exposure.

With a low MCV, ferritin is often also measured, your iron store. To learn how that works, read how to detect iron deficiency with a blood test. Important: do not start iron pills on your own. With thalassaemia extra iron does not help and may even accumulate undesirably.

What does a high MCV (macrocytic) mean?

A high MCV means your red blood cells are larger than normal, which doctors call macrocytosis. The cause is often a deficiency of vitamin B12 or folate, two substances needed for cell division. According to the NHG anaemia guideline, among others, a B12 deficiency is a common reason for a raised MCV in the Netherlands. Other causes are prolonged heavy alcohol use, a slow thyroid and certain medicines.

A B12 or folate deficiency can go together with tingling in hands or feet, concentration problems or pale skin. Read more in our guide to vitamin B12 deficiency.

What is the difference between MCV, MCH and MCHC?

MCV, MCH and MCHC together describe your red blood cells, but each from a different angle. MCV is about size, MCH about the amount of haemoglobin per cell and MCHC about how concentrated that haemoglobin is. Doctors always read them in combination. A small, pale cell (low MCV and low MCHC) classically fits with iron deficiency.

Why you should not start supplements on your own

It is tempting to head straight to the supplement shop with an abnormal MCV, but that is often unwise. The direction of the deviation determines which cause is likely, and those causes call for different approaches. If you take iron while your high MCV is due to a B12 deficiency, you solve nothing and delay the right treatment. If you take iron while your low MCV belongs to thalassaemia, iron may even accumulate undesirably. So only start supplementing after the cause has been confirmed with a blood test and you have discussed it with a doctor. A targeted test of your iron status or vitamins gives the direction; you agree the right dose and duration with your GP. That way you avoid treating a symptom without knowing its source.

What questions can you ask your doctor about your MCV?

• Does this MCV value fit my symptoms, such as fatigue?
• Could my diet or medication play a role?
• Which follow-up tests are worthwhile: iron, ferritin, B12 or folate?
• When is it useful to have blood drawn again?

To map your red blood cells more broadly, an anaemia panel can measure MCV alongside iron, ferritin and vitamins.

Frequently asked questions

Can my MCV be normal while I still have anaemia?

Yes, that can happen with normocytic anaemia. Your red blood cells are then normal in size, but there are too few of them or they contain too little haemoglobin. Chronic disease and kidney problems can play a role.

How long until MCV normalises after treatment?

Red blood cells live about 120 days on average. So it can take 2 to 4 months for the MCV to reset after a deficiency is addressed.

Is MCV measured as standard?

Yes. MCV is part of the standard blood count and is included automatically in almost any full blood test.

Sources

• NHG (Dutch College of General Practitioners). NHG anaemia guideline. Accessed 2026.
• RIVM (National Institute for Public Health). Vitamin and mineral status of the Dutch population. Accessed 2026.

Every blood test result at Vitalcheck includes a professional assessment by a BIG-registered doctor. Always discuss treatment decisions with your own GP.