Why your ferritin matters more than your haemoglobin

Anaemia is the last stage, not the first

Iron depletion happens in order. First the stores empty — that is ferritin falling. Then the machinery for making red cells starts to run short, and things like transferrin saturation change. Only at the end does haemoglobin drop far enough to be called anaemia.

The problem is that a standard GP full blood count measures haemoglobin. A woman can lose most of her iron stores, feel exactly as flat as you would expect, and be told her bloods are normal — because at that point they are.

What 'normal' means on a lab report

Reference ranges describe the middle of a population, not the level at which you will feel and perform well. Many UK labs flag ferritin as low only below about 15 µg/L. The symptomatic literature, and most sports medicine practice, treats anything under 30 as depleted and often aims considerably higher for endurance athletes.

The one complication worth knowing: ferritin also rises with inflammation, so a value taken shortly after a hard training block or an infection can look reassuring when the stores underneath are not. This is why a good report reads ferritin alongside CRP rather than on its own.

Raising it, and how long it takes

Food first: red meat and offal are the most bioavailable sources by a distance; plant iron is absorbed far less well, though vitamin C alongside it helps and tea alongside it does not. Where supplementation is needed, alternate-day dosing is now generally better supported than daily, because daily doses drive up hepcidin and blunt absorption.

Rebuilding stores takes months, not weeks. Three months is a fair expectation before a re-test says anything meaningful, which is exactly why the re-test sits where it does.

• 01

  Ask for ferritin explicitly; a full blood count will not show it

  What to request
• 02

  Read it alongside CRP, because inflammation lifts it

  The catch
• 03

  Alternate-day dosing beats daily for absorption

  If supplementing