Mean Corpuscular Volume (MCV)
The average size of your red blood cells. It helps show whether they run smaller or larger than usual.
AI-verified against cited sources. Awaiting expert reviewAlso called MCV, VCM, VGMLOINC 787-2
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What it is
Mean corpuscular volume (MCV) is the average size of your red blood cells, measured in femtoliters (fL). It is part of a routine complete blood count (CBC). Most blood-count machines measure it directly as cells pass through a small opening or a beam of light. Clinicians use it as an early clue to why your red cell count or hemoglobin might be low.
Why it matters
Size is a useful clue because different causes tend to push it in different directions. Smaller cells (low MCV) are most often linked to low iron or to thalassemia trait, an inherited difference in hemoglobin that usually causes no symptoms. Larger cells (high MCV) are linked to low vitamin B12 or folate, regular alcohol use, some medicines, and thyroid or liver conditions. MCV can sit outside the usual range even when hemoglobin is normal. Then it is usually something to mention at a routine visit.
If it’s low
A low MCV means your red blood cells are smaller than average. This is called microcytosis. The most common reasons are low iron and thalassemia trait. Your clinician can use your hemoglobin, your ferritin (a measure of iron stores) and your history to tell them apart.
Common causes
- Low iron stores or iron deficiency anemia, the most common cause in the United States
- Thalassemia trait, an inherited difference in hemoglobin that usually causes no symptoms
- Long-term inflammation or chronic disease
- Slow blood loss, such as heavy periods or bleeding in the digestive tract, which can lead to low iron
- Lead exposure
- Sideroblastic anemia and other less common blood conditions
What can help
- Ask whether a ferritin test is a good next step. Clinical reviews suggest it as the first test for small red cells
- Tell your clinician about heavy periods, blood in your stool or black stools
- If your ferritin is normal, ask whether more testing for thalassemia trait is worthwhile
If it’s high
A high MCV means your red blood cells are larger than average. This is called macrocytosis. About 3 in 100 people have an MCV above 100 fL, and it often has an ordinary explanation. A clinician can look at your hemoglobin, your other results and your history to put it in context.
Common causes
- Regular alcohol use, one of the most common causes
- Low vitamin B12 or folate
- Some medicines, including certain HIV, seizure, chemotherapy, antibiotic and diabetes medicines
- Liver disease
- An underactive thyroid (hypothyroidism)
- Young red blood cells (reticulocytes) released after bleeding or red cell breakdown, which are slightly larger
- A sample effect (uncommon): cold agglutinins, very high blood sugar or a very high white cell count can make MCV read falsely high
- Bone marrow conditions such as myelodysplastic syndromes (less common)
- Sometimes no clear cause is found
What can help
- Ask whether a vitamin B12 level should be checked, since it is a common first step for a high MCV
- Ask whether folate, thyroid and liver tests make sense for you
- If you drink alcohol regularly, talk about it with your clinician. MCV usually comes back down after a person stops drinking
- Review your medicines and supplements with your clinician or pharmacist
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
For adults: 80–100 fL. Source: Oregon Health & Science University Lab Services, American Family Physician, Labcorp, ARUP Laboratories, MedlinePlus, National Library of Medicine, Parkview Health Laboratory.
- 18+ (this one applies)80–100 fL
Sources: Oregon Health & Science University Lab Services, American Family Physician, Labcorp, ARUP Laboratories, MedlinePlus, National Library of Medicine, Parkview Health Laboratory
See MCV by age and sex, with the U.S. survey numbers where they exist.
If this applies to you
MCV means a little more for some people. Open the one that fits you.
Low iron or anemia
Low iron tends to make red cells smaller (low MCV) and paler (low MCH). BSG notes these changes are less reliable alongside chronic illness, thalassemia or low B12 or folate, and that thalassemia can cause small cells even when iron studies are normal.
Taking methotrexate
MCV is the average size of red blood cells. The BSR lists a raised MCV among the results that should prompt a call to the rheumatology team.
How common is your level?
NHANES describes the US civilian, non-institutionalized population, not a 'healthy' reference group. People with disease, on medication, fasting or not (except fasting-subsample markers), smokers and so on are all included. A percentile says where a value sits among Americans of that sex and age, not whether it is normal.
Use the left and right arrow keys to read each age. Shift moves five years.
Reference data derived from CDC/NCHS National Health and Nutrition Examination Survey (NHANES), cycles 2015-2016, 2017-March 2020 (pre-pandemic), August 2021-August 2023. Analysis by bloodtesttracker.com; not endorsed by CDC, NCHS or HHS.
Explore MCV by age and sex: every percentile as a table, with a download.
What can affect your result
- Age: children and teenagers have different normal ranges, so adult ranges do not apply to them
- Sex: some labs print separate adult ranges for men and women, and many do not
- Ancestry: thalassemia trait, a common cause of small red cells, is more common in people with roots in Africa, the Mediterranean, the Middle East, India and Southeast Asia
- Pregnancy: iron needs go up, and a low MCV in pregnancy usually leads to further checks
- Alcohol, some medicines, and low vitamin B12 or folate can raise MCV
- Low iron and slow blood loss can lower it
- Recent bleeding or a blood transfusion
- The analyzer and how the sample was handled can shift results slightly
- Cold agglutinins (red cells clumping in a cool sample) can make MCV read falsely high.
- Very high blood sugar or a very high white cell count can make some analyzers overestimate MCV.
- A recent blood transfusion mixes donor red cells with your own.
- Samples that wait too long before testing can give less reliable results. Labs set their own time limits.
- Different analyzers can read the same blood slightly differently.
Weeks to a few months. Red blood cells live for roughly 3 to 4 months, so the average size shifts only as old cells are replaced.
When to talk to a clinician
A mildly high or low MCV with a normal hemoglobin is usually something to bring up at a routine visit. Contact a clinician soon if your MCV is outside the range and your hemoglobin is also low (below 13 g/dL in men or 12 g/dL in women, the WHO anemia cutoffs), or if you have unusual tiredness, shortness of breath, pale skin, numbness or tingling, or a sore tongue. Call 911 or your local emergency number for chest pain, fainting, severe shortness of breath or confusion.
Questions you could ask
- Has my MCV changed compared with my past results?
- How does my MCV fit with my hemoglobin and other blood counts?
- Should we check my vitamin B12 and folate levels?
- Could any of my medicines or supplements be affecting my MCV?
- Would thyroid or liver tests help put this in context?
- Should we check my ferritin or other iron tests?
Questions people ask
What do microcytic, normocytic and macrocytic mean?
They describe red cell size. Microcytic means smaller than usual (an MCV under about 80 fL), normocytic means typical size, and macrocytic means larger than usual (over about 100 fL). Each lab sets its own exact cutoffs.
Can my MCV be normal if I'm low in iron?
Yes. In one clinical review, up to 40% of people with iron deficiency anemia had normal-sized red cells. A normal MCV does not rule out low iron. Ferritin and other iron tests give a more direct answer.
My MCV is a little high but my other results are in range. What could that mean?
It is a common finding. About 3 in 100 people have an MCV above 100 fL. Common reasons include regular alcohol use, some medicines, and low vitamin B12 or folate. Sometimes no cause is found. Your clinician can decide whether any follow-up tests make sense.
Is MCV used in biological age scores?
Yes, in one. The PhenoAge clock, published in 2018, uses MCV as one of nine blood inputs, and a higher MCV pushes the estimated age up. It is a research tool, not a medical test, and one number rarely tells the whole story.
Show the science and sources
Units
- 1 fL = 1 fL
- 1 fL = 1 µm³
Is a change real?
MCV naturally varies about 0.75% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 2% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Systematic review and meta-analysis of within-subject and between-subject biological variation estimates of 20 haematological parameters (Coskun A et al., EFLM WG-BV).
For clinicians and researchers
MCV is the mean of the red cell volume distribution. Current analyzers measure it directly (impedance or flow-cytometric light scatter) and calculate hematocrit as MCV × RBC. Older instruments measured hematocrit and derived MCV as Hct × 10 / RBC. Adult cutoffs of 80 fL (microcytosis) and 100 fL (macrocytosis) are conventional, though one AAFP review notes continuing debate about the upper limit, and about 3% of the general population is above 100 fL. Microcytosis is most often iron deficiency or thalassemia trait. Up to 40% of people with iron deficiency anemia have normocytic cells, and serum ferritin is the recommended first test for microcytosis. A low MCV in pregnancy warrants hemoglobin electrophoresis (AAFP consensus recommendation). Macrocytosis is split into megaloblastic causes (B12 or folate deficiency, with macro-ovalocytes and hypersegmented neutrophils) and non-megaloblastic causes (alcohol, usually under 110 fL; liver disease; hypothyroidism; reticulocytosis; myelodysplasia; drugs). Spurious macrocytosis comes from cold agglutinins, hyperglycemia (osmotic swelling during dilution on some analyzers) and marked leukocytosis (turbidity). Interpret MCV with RDW, reticulocyte count and a smear. MCV is one of nine blood inputs to the PhenoAge clock (Levine 2018), where a higher value raises the estimated age. Ranges differ between analyzer platforms. Pediatric intervals shift markedly with age, for example about 70–86 fL at 6–23 months at both ARUP and OHSU.
LOINC 787-2 (primary), 30428-7. Specimen: whole-blood.
Sources
- CBC with Differential: reference ranges (OHSU Lab Services test directory), Oregon Health & Science University Lab Services
- Evaluation of Microcytosis, American Family Physician (2010)
- Evaluation of Macrocytosis, American Family Physician (2009)
- Iron Deficiency Anemia: Evaluation and Management, American Family Physician (2013)
- Alpha- and Beta-thalassemia: Rapid Evidence Review, American Family Physician (2022)
- Sample report, CBC, Platelet, No Differential (test 028142), Labcorp (2020)
- Sample report, CBC With Differential/Platelet (test 005009), Labcorp
- CBC with Platelet Count and Automated Differential (ARUP test 0040003), reference intervals effective March 1, 2021, ARUP Laboratories (2021)
- RBC indices, MedlinePlus, National Library of Medicine
- Complete Blood Count with Differential (Parkview Laboratory test directory), Parkview Health Laboratory
- MCV: Mean Corpuscular Volume (conversion and formula reference), UnitsLab
- Answer to Case on Crazy CBC Values (cold agglutinin disease), The Blood Project
- An epigenetic biomarker of aging for lifespan and healthspan, Aging (2018)
- Measurement of Red Cell Lifespan and Aging, Transfusion Medicine and Hemotherapy (2012)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.