Mean cell volume
What this test measures
The mean cell volume is the average size of the red blood cells, measured in femtolitres (a millionth of a millionth of a millilitre). Small cells give a low MCV and large cells a high one. It is one of the most useful clues to why a haemoglobin might be low.
Why doctors request it
It is part of the full blood count. Doctors use it to sort anaemia into small-cell, normal-cell and large-cell types, which points them towards the most likely causes and the next tests to request.
What commonly pushes it up
- Alcohol
- Low vitamin B12 or folate
- An underactive thyroid
- Liver disease
- Some medicines, including some used for epilepsy, HIV and cancer
- A high reticulocyte count, because young red cells are larger
- Some bone marrow conditions
What commonly pushes it down
- Low iron
- Thalassaemia trait
- Long-term inflammatory illness
- Lead exposure
- Some inherited red cell conditions
Everyday reasons for a value outside the range
- A sample that has sat for a day or more before analysis reads higher, because the cells swell
- Moderate regular alcohol intake nudges it up without other illness
- Small differences between analysers are common
About the sample
No fasting needed. Changes slowly, over weeks to months, because red cells live around 120 days.
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Read my report freeThis is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.