Ferritin
A measure of your iron stores, which drops long before anaemia shows up.
What it means
The protein that stores iron, and the best single measure of how much iron you have in reserve.
It falls before your haemoglobin does, which means you can be iron deficient — tired, breathless, struggling to concentrate — with a completely normal full blood count.
It also rises with any inflammation, so a normal ferritin alongside a raised CRP does not exclude iron deficiency. That combination catches people out.
In practice
On iron studies, anaemia investigations and most health screening panels.
Often reported as "low normal", which is a phrase worth questioning — the bottom of the reference range is not necessarily fine if you have symptoms.
Why it matters
If you are a man, or over 50, and your ferritin is low: ask what is being done to find the cause. This is the single most important sentence on this page.
Iron deficiency in those groups warrants investigating the bowel, because slow blood loss is a leading cause. Taking iron tablets and feeling better hides the problem rather than solving it, and it is a recognised route to a delayed bowel cancer diagnosis.
In menstruating women the commonest cause is periods, and supplementing is usually reasonable — but heavy bleeding is itself worth assessing.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026