Typical reference ranges
| Index | Typical range | Low suggests | High suggests |
|---|---|---|---|
| MCV (cell size) | 80–100 fL | Iron deficiency, thalassaemia trait | B12/folate deficiency, alcohol, liver disease |
| MCH (Hb per cell) | 27–33 pg | Iron deficiency, thalassaemia | B12/folate deficiency |
| MCHC (Hb concentration) | 32–36 g/dL | Iron deficiency | Hereditary spherocytosis, sample issues |
| RDW (size variation) | 11.5–14.5% | Rarely significant | Iron, B12 or folate deficiency |
| RBC count | M 4.5–5.9 / F 4.0–5.2 ×10¹²/L | Anaemia | Thalassaemia trait (high count with low MCV), dehydration |
| Hematocrit (PCV) | M 40–50% / F 36–46% | Anaemia | Dehydration, polycythaemia |
Ranges based on: MedlinePlus; NHS; BSH. Full references are listed at the end of this page.
Use your own lab's range. Reference ranges differ between labs, analysers and methods, and with age, sex and pregnancy. The range printed on your report takes priority over the figures here.
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General information only, not a diagnosis. Your lab's printed range takes priority.
Small red cells: iron deficiency or thalassaemia trait?
Both give a low MCV and MCH, and both are very common in Pakistan, India, the Gulf and the Mediterranean. Some clues on the CBC: in thalassaemia trait the red cell count is often normal or high and the RDW usually normal, while iron deficiency tends to lower the red cell count and raise the RDW. These clues are not reliable on their own. Doctors confirm the cause with ferritin (low in iron deficiency) and hemoglobin electrophoresis or HPLC (for thalassaemia trait). This matters, because iron does not help thalassaemia trait, and couples who both carry the trait can have a child with thalassaemia major.
Large red cells
A raised MCV is seen with vitamin B12 or folate deficiency, regular alcohol use, liver disease, an underactive thyroid, some medicines such as methotrexate and some HIV drugs, and pregnancy. Very high values with low counts of other cells need prompt review.
MCHC and RDW
MCHC is rarely abnormal on its own; a high value can be a sample artefact or a sign of hereditary spherocytosis. RDW measures how varied the cell sizes are, and rises early in iron, B12 and folate deficiency, sometimes before the hemoglobin falls.
Frequently asked questions
What does low MCV and MCH mean?
Your red cells are small and pale. Iron deficiency and thalassaemia trait are the commonest causes; ferritin and Hb electrophoresis tell them apart.
What is PCV on my report?
Packed cell volume, the same as hematocrit: the share of blood made up of red cells.
Is high RDW serious?
Usually not on its own. It often points to iron, B12 or folate deficiency.
Should I take iron if my MCV is low?
Not before checking ferritin. Iron does not help thalassaemia trait and too much iron is harmful.
Sources and references
- MedlinePlus: Red Blood Cell (RBC) Indices
- NHS: Thalassaemia
- BSH: Guideline for the laboratory diagnosis of iron deficiency
- Gloucestershire Hospitals NHS: Haematology reference ranges