Iron Deficiency Without Anaemia: Why "Normal Bloods" Can Miss It

A great many people are told their blood tests are normal, and remain exhausted. Sometimes that is because nothing was wrong. Quite often it is because the test that would have shown the problem was not requested.

Why a normal blood count is not the same as normal iron

The body loses iron in a specific order, and understanding that order explains everything else on this page.

1. Iron stores fall first. The body draws down its reserves. Ferritin — which reflects those stores — drops
2. Then the supply to tissues tightens. Symptoms usually begin here
3. Only last does haemoglobin fall, which is the point at which anaemia is diagnosed

Anaemia is the end of the process, not the beginning. A full blood count only detects stage three. By the time haemoglobin is low, iron stores have been empty for some time — and someone can spend a year or more genuinely symptomatic while every full blood count comes back reassuringly normal.

The practical consequence: ask for ferritin by name. It is not included in a standard full blood count and it will not be measured unless it is requested.

The trouble with the ferritin "normal" range

Two problems, and both cause deficiency to be dismissed.

The lower limit is set very low

Many laboratories flag ferritin only below 15 or below 30 µg/L. But symptoms commonly begin well above those thresholds, and restless legs and fatigue in particular often improve only once ferritin is brought up considerably higher. A result of 22 reported as "normal" may be nothing of the sort in someone symptomatic.

What matters is your number and your symptoms together, not whether the printout has an asterisk beside it.

Ferritin rises with inflammation — and this is the trap

Ferritin is an acute phase protein. It goes up with infection, inflammation, liver disease, excess weight and recent illness — entirely independently of how much iron you have.

So someone with genuine iron deficiency and any inflammation can produce a perfectly normal-looking ferritin. The way round it is to measure CRP at the same time. A normal ferritin alongside a raised CRP should not be taken at face value, and transferrin saturation is a useful additional measure in that situation. This is a common and entirely avoidable miss.

What it feels like

Iron does far more than carry oxygen — it is involved in energy production and in dopamine synthesis — which is why the symptoms range so widely:

• Fatigue that sleep does not fix, and breathlessness on stairs or hills
• Hair shedding — more coming out in the brush or the shower
• Restless legs — an urge to move the legs at night. Strongly associated with low iron and often dramatically better once it is corrected
• Poor concentration and brain fog
• Feeling cold, particularly hands and feet
• Brittle or spoon-shaped nails; cracks at the corners of the mouth; a sore, smooth tongue; recurrent mouth ulcers
• Craving and chewing ice, or other non-food substances. Unusual, near-specific to iron deficiency, and worth mentioning — it tends to resolve within days of treatment
• Generalised itching, which is under-recognised

Finding out why — this part is not optional

Iron deficiency is a finding, not a diagnosis. The important question is always where the iron went.

The safety point that matters most

Unexplained iron deficiency in a man of any age, or in a woman past the menopause, requires investigation of the gut — usually endoscopy and colonoscopy.

It is one of the recognised presentations of bowel and stomach cancer, and it can be the only one. Being handed iron tablets without that investigation is a genuine failure of care, and it is worth asking about explicitly rather than assuming it has been considered.

In women who are still menstruating

Heavy periods are far and away the commonest cause — and one of the most consistently normalised. If you soak through protection in under two hours, pass clots larger than a 10p piece, or plan your life around your period, that is heavy bleeding, whatever you have been told, and it is treatable.

Other causes worth excluding

• Coeliac disease — which frequently presents as iron deficiency with no bowel symptoms at all. Test while still eating gluten
• Long-term omeprazole or lansoprazole, which reduce iron absorption — commonly overlooked
• Vegetarian and vegan diets, where plant iron is absorbed less efficiently
• Regular blood donation; endurance running; pregnancy and breastfeeding; NSAIDs causing slow gut bleeding

Taking iron properly — the part that has changed

Alternate-day dosing works as well as daily, and is far better tolerated. This is a genuine shift and most people have not heard it.

Taking iron triggers a hormone called hepcidin, which then blocks absorption for the next 24 hours or so — meaning a second daily dose is largely wasted while still causing all the side effects. One tablet every other day frequently raises ferritin as effectively as one or two daily, with much less nausea and constipation.

The rest:

• Take it with vitamin C — orange juice, or a supplement. It meaningfully improves absorption
• Avoid tea, coffee, milk and calcium supplements within two hours. Tannins and calcium markedly reduce uptake, and a cup of tea with the tablet undoes much of the benefit
• Expect black stools. Normal, and not to be confused with the tarry black of gut bleeding — iron gives a dull black with no particular smell
• For constipation: fluid, fibre, and a stool softener rather than abandoning the treatment

How long

Continue for at least three months after the blood count normalises — that period is what refills the stores rather than merely correcting the anaemia. Stopping as soon as haemoglobin recovers is why so many people relapse within the year.

An iron infusion is an option where tablets are not tolerated, absorption is impaired, or replacement is needed quickly. It works within weeks rather than months.

What to ask for

If you are tired and have been told your bloods are fine, the useful request is specific:

"Could I have ferritin, CRP, a full blood count, B12, folate, thyroid function and coeliac screening — and could you tell me the actual ferritin number rather than whether it was flagged?"

The number is the point. "Normal" covers a range wide enough to include people who feel perfectly well and people who can barely get up the stairs.