Glossary term
MCV
Also known as: Mean Corpuscular Volume, Mean Cell Volume
Part of: Blood Test Results
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- Last reviewed
- Last reviewed January 1970
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- Written in plain English
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- Reviewed by Medipher Editorial Team
The average size of your red blood cells.
Medipher explains medical wording in plain English — it does not diagnose or replace a clinician. If this is a medical emergency, call your local emergency number immediately.
Simple visual explanation
What is this?
MCV stands for Mean Corpuscular Volume — a measurement of the average size of your red blood cells.
Red blood cells that are smaller than usual (low MCV, called 'microcytic') or larger than usual (high MCV, called 'macrocytic') give clinicians important clues about the cause of anaemia.
MCV is reported automatically as part of a Full Blood Count and is one of the first values clinicians look at when working out why haemoglobin is low.
Why is it important?
MCV is one of the most useful indices for classifying anaemia. On its own it doesn't diagnose a condition, but combined with haemoglobin and ferritin it usually points clearly to a cause.
The MCV pattern also helps clinicians decide which follow-up tests are most useful, which saves time and unnecessary investigations.
Where you'll see it: Full Blood Count (FBC / CBC) reports as MCV, usually in femtolitres (fL).
How doctors use this result
Clinicians may use this result to:
- Work out what type of anaemia is present.
- Decide whether to test ferritin, B12 and folate next.
- Look for clues about alcohol use, thyroid or bone-marrow conditions.
- Monitor the response to treatment such as iron or B12 replacement.
What's the normal range?
| Adults | 80–100 fL |
Values just outside this range are common and often not significant.
A few units above or below the printed range is common and, when haemoglobin is normal, rarely means something is wrong.
Normal ranges are guides, not verdicts. Interpretation depends on your age, sex, symptoms, medical history, medications and other investigations — which is why your clinician looks at the whole picture rather than a single value.
Common reasons it may be high
Vitamin B12 or folate deficiency
Both are needed to make normal red cells; without them, cells grow too large before release.
Heavy alcohol use
Alcohol interferes with red-cell production in the marrow, producing larger cells.
Underactive thyroid
Low thyroid hormone slows metabolism, including red-cell production.
Some medications
Certain drugs affect DNA synthesis in the marrow, resulting in larger cells.
Liver conditions
Changes to red-cell membranes in liver disease can raise the average size.
Common reasons it may be low
Iron deficiency
Iron is essential for haemoglobin; without it, red cells are smaller and paler.
Chronic inflammation
Long-standing illness can reduce the availability of iron for red-cell production.
Thalassaemia
An inherited difference in haemoglobin structure produces small red cells.
Does an abnormal result always mean something is wrong?
Not necessarily. A number that sits outside the printed range is a prompt for interpretation — not a diagnosis.
- A single result rarely gives the full picture — clinicians interpret it alongside your symptoms.
- Your medical history, medications and other blood tests all shape the meaning of one value.
- Small movements just outside the reference range are common and often not concerning.
- Repeat testing over time is frequently more useful than any single number.
What might happen next?
- Blood tests for ferritin, B12 and folate.
- A review of diet, alcohol use and medications.
- Further tests if an inherited condition is suspected.
One result rarely tells the whole story. Clinicians look at your symptoms, medical history, medications and other tests together — and a single value that sits slightly outside the reference range is often normal for you. Repeat testing over time is frequently more useful than any one number. Medipher helps you understand what a result means in plain English, but it cannot diagnose medical conditions or replace advice from a doctor, nurse or pharmacist.
When should I speak to a healthcare professional?
Speak with your GP or another healthcare professional if:
- You've been asked to repeat the test.
- You're experiencing new or worsening symptoms.
- Your clinician has flagged the result as needing follow-up.
- You don't understand your results or feel unsure what to do next.
If you have severe symptoms — chest pain, severe breathlessness, fainting, heavy bleeding or feel very unwell — seek urgent help. If this is a medical emergency, call your local emergency number immediately. Medipher is designed to help explain medical information and is not an emergency service.
Frequently asked questions
Related blood tests
Terms clinicians often look at alongside MCV.
- HaemoglobinThe protein inside red blood cells that carries oxygen from your lungs to the rest of your body.
- Red Blood CellsThe cells in your blood that carry oxygen. They contain haemoglobin, which does the actual oxygen carrying.
- AnaemiaA condition where you don't have enough healthy red blood cells or haemoglobin to carry oxygen around your body.
Related guides
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Sources
General patient information referenced when writing this page.
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Continue learning
- Next upHaemoglobinThe protein inside red blood cells that carries oxygen from your lungs to the rest of your body.
- Next upRed Blood CellsThe cells in your blood that carry oxygen. They contain haemoglobin, which does the actual oxygen carrying.
- Next upAnaemiaA condition where you don't have enough healthy red blood cells or haemoglobin to carry oxygen around your body.
This glossary entry is general health information, not medical advice. Medipher explains medical wording in plain English and does not diagnose, provide treatment advice, or replace a GP, doctor, nurse or pharmacist. Always discuss your results with a qualified clinician.