Low Ferritin: Exhausted With a Normal Blood Test

You went to the doctor exhausted. They tested for anaemia, your haemoglobin came back normal, and you were told your iron is fine. You went home still exhausted, still losing hair, still cold in a warm room, sitting there in a jumper in July like a small offended ghost.

Haemoglobin and iron stores are not the same measurement. Low ferritin with a normal full blood count is extremely common in menstruating women, and it is one of the most frequently missed explanations for the kind of tiredness that sleep does not touch.

Ferritin is the savings account

Haemoglobin is the iron currently circulating and doing its job. Ferritin reflects what you have in reserve.

You can run your reserves down almost to nothing while haemoglobin stays in range, because your body prioritises circulating red cells and quietly empties the store to do it. Anaemia is the late stage, not the first sign. By the time it shows up on a full blood count, the depletion has usually been running for a long time.

Evidence: Strong that ferritin reflects iron stores. Mixed on where the threshold should sit. Many UK labs flag below 15µg/L. A great deal of clinical opinion and a reasonable body of research suggests symptoms are common below 30, and that levels under 50 may matter for hair and fatigue — which is why so many women fall into the gap between “not flagged” and “not well”.

What low iron stores feel like

Fatigue that rest does not fix. Breathlessness on stairs you used to manage. Hair shedding several months after the depletion started. Feeling cold constantly. Poor exercise recovery. Restless legs at night. Brittle nails. Difficulty concentrating.

Notice how many of those overlap with a thyroid problem, with poor sleep, and with simply being busy. That overlap is exactly why it gets attributed to something else.

“Your iron is fine” usually means your haemoglobin is fine. Those are different questions, and only one of them was asked.

What to ask for

Ask specifically for ferritin, alongside a full blood count and CRP. CRP matters because ferritin rises with inflammation — so a normal-looking ferritin during an infection or a flare can be falsely reassuring.

Ask for your actual number rather than accepting “normal”. Being at the very bottom of a range is a meaningfully different situation from sitting comfortably in the middle of it. The lab request script covers how to ask without it becoming a negotiation.

Also worth requesting: thyroid function and vitamin B12, since these often travel together and produce a similar picture.

Raising it

Food first, but be realistic. Red meat, liver, sardines, lentils, beans, tofu and dark leafy greens all contribute. Plant iron is absorbed less readily, so pair it with vitamin C — peppers, citrus, tomatoes — in the same meal.

Keep tea and coffee away from iron-rich meals. The tannins substantially reduce absorption. An hour either side is enough, and this one change matters more than most people expect.

If you supplement, do it properly. Evidence: Moderate to strong that alternate-day dosing is absorbed better than daily dosing, because a daily dose raises hepcidin, the hormone that blocks further absorption. Taking less, less often, frequently works better and is considerably gentler on your stomach.

Give it three to six months. Refilling a store takes far longer than correcting haemoglobin, and stopping as soon as you feel better is how people end up back where they started, roughly the iron-supplement equivalent of quitting antibiotics on day two because you feel fine now, thanks.

Do not self-prescribe iron indefinitely

Iron supplements are not harmless. Some people carry haemochromatosis, a genetic condition causing iron overload, and supplementing into that is dangerous. Take iron because a test showed you need it, and retest rather than continuing indefinitely on assumption.

Heavy periods are the most common cause here, and heavy bleeding is itself worth investigating rather than absorbing. Persistent low iron in someone who is not menstruating heavily needs a proper look at absorption — coeliac disease is a common finding — and at the gut generally.

Questions people actually ask

What ferritin level causes symptoms?

Many labs flag below 15µg/L, but symptoms are commonly reported below 30, and some clinicians treat below 50 where fatigue or hair loss is present. Thresholds vary, so discuss your actual number with your doctor.

Can you have low ferritin without anaemia?

Yes, and it is common. Iron stores deplete first while haemoglobin stays in range, so a normal full blood count does not rule it out.

Is alternate-day iron really better?

Studies suggest alternate-day dosing improves absorption compared with daily dosing, because daily doses raise hepcidin and block uptake. It also tends to cause fewer digestive side effects.

More in the nutrition section.