Iron Panel (Iron, TIBC, Transferrin Saturation)

Stores empty long before haemoglobin falls, so a normal CBC is routinely used to tell people their iron is fine. The fatigue, hair shedding, breathlessness and restless legs arrive in this phase, not the anaemic one.

Find the cause, do not just supplement — heavy periods, gut blood loss, coeliac, over-donation. Unexplained iron deficiency in a man or a postmenopausal woman warrants gastrointestinal evaluation. Iron bisglycinate, alternate-day, with vitamin C.

Ferritin rises with inflammation, so a high value usually means inflammation rather than iron. When CRP is normal and saturation is genuinely high, iron overload moves up the list.

Saturation above 45% with a normal CRP is the combination that warrants haemochromatosis genetic testing — it is common, easily treated early, and does organ damage if it is missed for decades. Stop any iron supplement until this is sorted.

This is the other thing small red cells mean, and the discriminator is the red cell COUNT rather than the size. In iron deficiency the marrow makes fewer cells and smaller ones, so MCV and RBC both fall. In thalassaemia trait it makes a normal or high number of small cells — so a low MCV sitting next to a high RBC is pointing away from iron. That relationship is the Mentzer index: MCV divided by RBC in millions per microlitre. Below 13 favours thalassaemia trait, above 13 favours iron deficiency. It is a screening steer and not a diagnosis, but it is free — the two numbers are already on your CBC. Thalassaemia trait is a carrier state, not a disease. Most people with it are entirely well and simply run a low MCV for life.

Do not iron-load on the assumption it is deficiency. If your ferritin and iron saturation are normal, extra iron has nowhere useful to go and iron overload does real damage. This is the case where the wrong treatment is actively harmful rather than merely useless. Haemoglobin electrophoresis (or HbA2) settles it, once, permanently. It is worth knowing your own answer rather than re-litigating a low MCV at every blood test for the rest of your life. It also matters for family planning — two carriers can have a child with the full condition, which is a genuinely different conversation.

Ferritin is an acute-phase reactant — it rises with inflammation regardless of how much iron you actually have stored. So inflammation can hold ferritin in the normal range, or push it above it, while your iron stores are genuinely empty. The number that gives it away is iron saturation, which stays low because the iron is being sequestered rather than used. This is anaemia of inflammation, and it is a signpost rather than a diagnosis: the inflammation is the thing to explain. Chronic infection, autoimmune disease, obesity, inflammatory bowel disease and hard unrecovered training all produce it. It is the mirror image of the usual mistake. Most people are told their ferritin is fine and stop looking; here, ferritin being fine is the finding.

Read ferritin and hs-CRP together, always. A ferritin taken during any inflammatory state cannot be interpreted alone, and re-drawing it when you are well often reveals a completely different number. Chase the inflammation, not the iron. Supplementing into an inflammatory block mostly does not work, because the block is the point — your body is deliberately withholding iron. Finding and treating the cause is what releases it. If the hs-CRP has no obvious explanation, that is worth a clinician rather than a supplement.