An MCV of 66.5
66.5 fL
Markedly microcytic
MCV of 66.5 fL is well below the reference range — markedly small red cells by commonly reported adult reference ranges
| Where it fallscommonly reported adult reference ranges | Markedly microcytic |
|---|---|
| MCV | 66.5fL |
| Usual reference range | 80 – 100fL |
| Markedly microcyticthis reading | under 70fL |
| Microcytic | 70 – 79.9fL |
| Normocytic | 80 – 100fL |
| Macrocytic | 100 – 114.9fL |
| Markedly macrocytic | 115 and abovefL |
Notes
- One reading is not a diagnosis. MCV moves with iron status, B12 and folate, alcohol, thyroid function and some medicines. A clinician reads it against your history and usually against a repeat, not on its own.
- Reference ranges differ between laboratories. The bands above follow commonly reported adult reference ranges. Your own report prints the range its analyser was calibrated against, and that printed range is the one to compare against — a difference of a few units between labs is normal and does not mean either is wrong.
- MCV is the size of the average red cell, and its job is to sort anaemia into three families. Small cells point at iron deficiency above all, then thalassaemia trait, then chronic disease. Ferritin is the test that separates the first two, and in thalassaemia trait the red cell count is usually high while the haemoglobin is only mildly low — a combination iron deficiency does not produce.
- An MCV of 66.5 fL is an average, and averages hide mixtures. Someone with both iron deficiency (small cells) and B12 deficiency (large cells) can return a perfectly normal MCV. The RDW on the same report is what exposes it: a wide RDW with a normal MCV says the population is mixed, not uniform.
- MCV moves slowly. Red cells live about 120 days, so the value reflects what the marrow has been producing for months. It is a poor way to check whether a treatment started last week is working, and a normal MCV does not rule out a deficiency that began recently.
What mcv of 66.5 fL means
A result of 66.5 fL falls in Markedly microcytic by commonly reported adult reference ranges.
The usual reference range is 80 – 100 fL.
Reading it next to the rest of the panel
Almost no blood test answers a question on its own. Each one narrows the field, and what narrows it further is the value sitting beside it on the same report — which is why a printout with one figure circled is harder to interpret than the whole page.
The bands here come from a named source rather than a rounded rule of thumb. A threshold is a decision point somebody argued for in print, and knowing which document a line comes from is what separates a meaningful result from a borderline one.
Nearby sizes
Read more
- CBC Normal Ranges — What Each Line on the Result MeansA value marked high or low on a CBC is common and is often not significant on its own. The pattern across lines is what a clinician reads.
- eGFR Normal Range: Above 90, and the Stages Below IteGFR is an estimate built from creatinine, age and sex — and the estimate is better than the raw creatinine it comes from, for a reason worth understanding.
- TSH Normal Range: 0.4–4.0 mIU/L, and the Number Moves BackwardsTSH runs opposite to the gland it measures. High TSH means the thyroid is underactive, and that inversion catches almost everyone reading their own result.
- Cholesterol Numbers: What Total, LDL, HDL and Triglycerides MeanA lipid panel reports four numbers and the one printed largest — total cholesterol — is the least useful of them.