Stage 1: Iron stores fall (storage depletion)
In the first stage, your body's iron reserves start to run down. This is measured by ferritin, which reflects stored iron. Ferritin drops before anything else does, which is why it's the most useful early marker.
At this stage your haemoglobin (the number on a standard full blood count) is still normal, so a basic blood test can look reassuring even though your stores are already low. Many women feel tired at this point but are told their 'blood count is fine'.
Stage 2: Iron-deficient production
As stores empty, your body starts to struggle to make enough healthy red blood cells, even though the overall count hasn't dropped yet. Symptoms like fatigue, breathlessness and poor concentration often become noticeable here.
This is a key reason a full iron studies panel — not just a haemoglobin level — matters. It can catch deficiency in these earlier stages, when treatment is simpler.
Stage 3: Iron deficiency anaemia
In the final stage, iron is so low that haemoglobin falls and you develop iron deficiency anaemia. Symptoms are usually more pronounced: marked fatigue, pallor, breathlessness and a racing heart.
The take-home message is that you can feel genuinely unwell in the earlier stages, before anaemia shows up. If you're symptomatic, ask for iron studies including ferritin, and see your GP about treatment and finding the underlying cause.
Related condition
Iron infusion / low iron →References & sources
This content is general information and not a substitute for individual medical advice. Please consult a GP for your personal situation.
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