What do the numbers mean?
| MCV (fL) | Label | Implication |
|---|---|---|
| Below 70 fL | Severely low | Significant microcytic anaemia — needs investigation |
| 70–80 fL | Low | Microcytosis — likely iron deficiency or thalassaemia |
| 80–100 fL | Normal | Standard red cell size |
| Above 100 fL | High | Macrocytosis — B12/folate deficiency or liver issues |
MCV is rarely looked at in isolation. Doctors read it alongside haemoglobin, RBC count, ferritin, and often B12 to determine the cause of anaemia — or to catch it before it becomes anaemia.
Normal vs Optimal — there is a difference
The normal range (80–100 fL) is wide. You can have an MCV of 81 — technically normal — alongside ferritin of 12 and haemoglobin trending downward, and the full picture tells a different story than any single number.
This is why a comprehensive view of your CBC (complete blood count) alongside iron studies and B12 matters far more than one flagged result. Low MCV with normal haemoglobin is often called iron deficiency without anaemia — and it can still cause significant symptoms.
Common symptoms you might notice
Common causes
- Iron deficiency — the most common cause worldwide, especially in menstruating women
- Thalassaemia trait — a genetic condition causing persistently small red cells
- Anaemia of chronic disease — often seen in autoimmune conditions or chronic infections
- Lead poisoning — rare, but causes microcytic anaemia
- Sideroblastic anaemia — a rarer condition affecting how iron is used in cells
- Chronic blood loss — from GI tract (ulcers, polyps) or heavy periods
Questions to ask your doctor
Copy these before your next appointment. Your doctor will appreciate that you came prepared.
- Is this low MCV linked to iron deficiency, or should we consider thalassaemia trait?
- Can we run a full iron panel — ferritin, serum iron, transferrin saturation?
- Is my haemoglobin affected, or is this pre-anaemia that we should treat now?
- Should we investigate for a source of blood loss — GI scope, for example?
- How quickly do you expect my MCV to respond to treatment?
Have this marker in your results?
See how your MCV fits with the rest of your CBC — ferritin, haemoglobin, and iron stores all in one view. Upload your full report and get a plain-English breakdown of every value — plus a personalised question list for your doctor.