MCV (mean corpuscular volume): what it means
What it measures
MCV (mean corpuscular volume) measures the average size of your red blood cells. It is usually reported as one part of a complete blood count (CBC).
Why it’s ordered
Clinicians order it to help check general health and to help evaluate anemia, especially when symptoms such as fatigue, weakness, shortness of breath, dizziness, or headache are present. The MCV helps categorize anemia by red-cell size to guide further testing.
General reference range
MedlinePlus lists a general MCV normal value of roughly 79 to 95 femtoliters (fL), but this is only a general guide. Reference ranges vary by laboratory, age, sex, and measurement method, and some labs use different measurements or samples. The range printed on your own lab report is the one that applies to your result. A result outside the range does not by itself mean you have a medical problem.
If it’s high
A high MCV (larger-than-average red cells, called macrocytic) is a general finding, not a diagnosis, and this is not a complete list. It may be seen with vitamin B12 or folate (folic acid) deficiency, pernicious anemia, liver disease, or certain treatments such as chemotherapy. Factors like diet, medications, and other conditions can also affect the result.
If it’s low
A low MCV (smaller-than-average red cells, called microcytic) is a general finding, not a diagnosis, and this is not a complete list. It can be seen with iron deficiency anemia (the most common form), thalassemia (an inherited blood disorder), or lead poisoning. Note that anemia can also occur with a normal MCV, for example with sudden blood loss, kidney failure, or aplastic anemia.
A result is not a diagnosis
Reference ranges vary by laboratory, age, sex, and method — the range on your own report is what applies to you. A single value out of range doesn’t confirm any condition; your clinician interprets it alongside your symptoms, history, and other results. This page is general information, not medical advice.
Medicines that can move this result
Hydroxyurea blocks the DNA building blocks a dividing red cell needs, so cells leave the marrow oversized. The label calls this macrocytosis self-limiting and says it is often seen early in treatment; it resembles pernicious anemia under the microscope but is not related to low vitamin B12 or folic acid — and because it can mask a genuine pernicious anemia, the label recommends prophylactic folic acid.
Source ↗Zidovudine interferes with DNA copying inside developing red cells, so they are released larger than normal. The FDA label documents this in pediatric trials, where most children given 180 mg/m2 every 6 hours developed macrocytosis. The size change itself causes no symptoms, and it is a separate finding from the anemia the same drug can cause.
Source ↗Valproic acid is a recognised cause of enlarged red cells. The mechanism is not established — the source lists it among drugs that induce macrocytosis without assigning a pathway — and the change is typically found on a routine blood count rather than because of any symptom.
Source ↗Methotrexate blocks folate, the vitamin a red cell needs to copy its DNA and divide, so precursor cells keep growing before they split. This is why folic acid is prescribed alongside methotrexate when it is used for rheumatoid arthritis or psoriasis.
Source ↗Long-term phenytoin impairs folate metabolism, and without enough folate the marrow turns out fewer, larger red cells — a well-recognised finding in people taking this seizure medicine for years.
Source ↗Trimethoprim, usually taken combined with sulfamethoxazole, blocks the folate-processing enzyme bacteria depend on. It acts far more weakly on the human version of that enzyme, but with high doses or prolonged courses the same block can slow red cell division and leave the cells enlarged.
Source ↗Metformin can reduce how much vitamin B12 you absorb, and low B12 makes the marrow produce oversized red cells. A high MCV on metformin is a reason to have a B12 level checked — the deficiency is correctable with supplementation — rather than a reason to stop the drug.
Source ↗Do not stop a prescribed medicine over a lab number. These are recognised associations, not a finding about your result — your value may have nothing to do with any medicine you take, and the list is not complete. Bring it to whoever prescribed the drug; they can weigh it against why you are taking it.
Frequently asked
- What does the MCV (mean corpuscular volume) test measure?
- MCV (mean corpuscular volume) measures the average size of your red blood cells. It is usually reported as one part of a complete blood count (CBC).
- What is a normal MCV (mean corpuscular volume) range?
- MedlinePlus lists a general MCV normal value of roughly 79 to 95 femtoliters (fL), but this is only a general guide. Reference ranges vary by laboratory, age, sex, and measurement method, and some labs use different measurements or samples. The range printed on your own lab report is the one that applies to your result. A result outside the range does not by itself mean you have a medical problem.
- What does a high result mean?
- A high MCV (larger-than-average red cells, called macrocytic) is a general finding, not a diagnosis, and this is not a complete list. It may be seen with vitamin B12 or folate (folic acid) deficiency, pernicious anemia, liver disease, or certain treatments such as chemotherapy. Factors like diet, medications, and other conditions can also affect the result.
- What does a low result mean?
- A low MCV (smaller-than-average red cells, called microcytic) is a general finding, not a diagnosis, and this is not a complete list. It can be seen with iron deficiency anemia (the most common form), thalassemia (an inherited blood disorder), or lead poisoning. Note that anemia can also occur with a normal MCV, for example with sudden blood loss, kidney failure, or aplastic anemia.
Other lab tests
Sources
General reference, not medical advice, and not a substitute for your clinician. Lab reference ranges and interpretation depend on the laboratory and on your individual situation — discuss your results with a licensed healthcare professional.