RDW/MCV Ratio

Compares how varied your red blood cell sizes are against their average size, as an early quality check on red cell production.

Last reviewedAugust 17, 2026

Whole blood

sample type

Calculated, no extra blood needed

blood needed

~10 days

results in app

Any time of day

best timing

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On this page

Why test Reference ranges What you'll learn What affects it How testing works Sources FAQ

In short

Two values from your blood count go into this ratio. RDW, the red cell distribution width, describes how much the size of your red blood cells varies. MCV, the mean corpuscular volume, is their average size.

Dividing one by the other gives a measure of variation relative to size. It is calculated from your existing blood count, so it needs no extra sample.

Blood Health (CBC & Iron)

Reviewed against DGKL reference practice.

Why test this?

Two people can have the same average red blood cell size and very different blood. One has cells that are all much the same, the other has a mix of small and large. This ratio captures that difference in a single number.

A rising ratio usually means your marrow is turning out red blood cells unevenly, which shows up early in iron, vitamin B12 or folate shortfalls, often before haemoglobin drops. A steady low ratio suggests production is consistent.

What is a normal result?

Aniva reads your result against research-backed ranges, not just the lab's wide normal. The reference shown below is specific to this biomarker.

Adult reference values as used by Aniva. Ranges are guidance and can vary by laboratory and method.

Group	Normal range
Adults	0.11 to 0.16 %/fL

Sources: MedlinePlus, National Library of Medicine: RBC Indices

Your Aniva report reads your result against these values together with your age, sex and the rest of your panel.

Ranges are guidance and vary by lab and assay, aligned with DGKL practice. Always read your result against your own lab's reference interval.

What insights will this test give you?

An early signal that red blood cell production has become uneven.
A hint towards iron, vitamin B12 or folate shortfalls before a full anaemia appears.
A single trendable number that sits alongside your other blood count values year over year.

What can affect this result?

What can skew the result

This is a calculated value, so anything that affects RDW or MCV affects it. Recent transfusion, a mix of two different deficiencies at once, liver disease and alcohol use all shift the underlying values. It supports a picture rather than making a diagnosis on its own.

Best interpreted with

Read together with RDW, MCV, haemoglobin, ferritin and vitamin B12, and next to the Mentzer index where thalassaemia trait is a question.

How is this tested?

Sample

Whole blood

Blood needed

Calculated, no extra blood needed

Method

Calculated

Best timing

Any time of day

Sources. The evidence behind this

MedlinePlus: RBC Indices

Common questions

What does a high RDW/MCV ratio mean? It suggests your red blood cells vary more in size than usual relative to their average, which often points to iron, vitamin B12 or folate running short.

Do I need an extra blood draw for this? No. It is calculated from values already in your blood count.

Do I need to fast? No. Eat and drink normally.

What can affect my result? Recent transfusion, two deficiencies at once, liver disease and alcohol use all move the underlying RDW and MCV.

How long do results take? Results are usually ready in about 10 days.

What should I discuss with my clinician? Ask how this sits next to your ferritin, vitamin B12 and folate, and whether the pattern warrants iron studies.

Which Aniva panels include this marker?

Core

Your annual full-body baseline with more than 100 biomarkers, included in your Aniva membership.