MCV (Mean Corpuscular Volume)

What is MCV

MCV (Mean Corpuscular Volume) is the average volume of red blood cells, measured in femtolitres (fL). This marker helps you understand whether your red blood cells are normal in size, too large (macrocytosis), or too small (microcytosis).

MCV is one of the most important markers for identifying the type of anaemia. Different cell sizes point to different causes, which is why doctors often start with this number.

Reference ranges

• Normal: 80–100 fL
• These limits are the same for men and women

MCV does not differ by sex, but may vary slightly depending on the laboratory and age.

Why MCV may be elevated (macrocytosis)

When MCV exceeds 100 fL, red blood cells are larger than normal. This is called macrocytosis. Possible causes:

• Vitamin B12 deficiency — one of the most common causes, especially in older adults and vegetarians
• Folate deficiency
• Alcohol consumption — even moderate drinking can raise MCV
• Liver disease
• Hypothyroidism
• Certain medications — methotrexate, valproate, azathioprine
• Myelodysplastic syndrome (less common)

Macrocytosis does not necessarily cause symptoms — it is often found incidentally on a full blood count.

Why MCV may be low (microcytosis)

When MCV is below 80 fL, red blood cells are smaller than normal:

• Iron deficiency — the most common cause worldwide
• Thalassaemia — an inherited haemoglobin disorder, more common in people of Mediterranean descent
• Anaemia of chronic disease — the body restricts iron availability due to inflammation
• Lead poisoning (rare)
• Sideroblastic anaemia (rare)

What to do with your results

MCV is best interpreted alongside other markers:

• Low MCV + low ferritin → iron deficiency anaemia most likely
• High MCV + low B12 → B12 deficiency anaemia likely
• High MCV + normal B12 and folate → worth evaluating liver function, thyroid hormones, and alcohol use

A single mild deviation (e.g. MCV 101 fL) is not a diagnosis in itself, but it is worth discussing with your doctor.

Tracking over time

MCV changes slowly because red blood cells live for about 120 days. New cells gradually replace old ones, so changes in MCV become apparent over weeks or months. This means a trend over time is more informative than a single measurement.

QbiLabs displays MCV as a chart — you can see whether the value is gradually rising, falling, or stable.

Questions for your doctor

1. What does my MCV value mean — do I need further investigation? 2. Is it worth checking B12, folate, and ferritin? 3. Could my lifestyle (diet, alcohol consumption) have affected this marker? 4. Are there inherited conditions (e.g. thalassaemia) that should be considered? 5. How often should I repeat this test?