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Iron, ferritin and fatigue: listen to your body after blood loss

By Kerri Hopkins · 5 min read · 20 October 2026

“I told myself that was normal with a baby.”

Kerri, founder of BioHer

My story

After I gave birth, I lost a lot of blood in labour. Then I had heavy periods for seven years. I was exhausted, and I told myself that was normal with a baby. I had blood clots every period, muscle and calf cramps, dizziness, a racing heartbeat, breathlessness, hair loss, and headaches that felt like a constant hangover. I did not know any of that was not normal. It was iron deficiency.

If you have had any kind of blood loss, such as childbirth, heavy periods or surgery, and you feel like this, please listen to your body. It could be iron deficiency.

What the NHS says

The NHS lists heavy periods and pregnancy as very common causes of iron deficiency anaemia. Common symptoms are tiredness, breathlessness, a racing heartbeat, pale skin and headaches. Less common ones include hair loss, tinnitus, a sore tongue and restless legs. Everyone is different, and these symptoms have many other possible causes, including an underactive thyroid, which is why testing matters.

Keep a symptom journal

Before you see your GP, write down:

• what you notice, and how often
• when it started and whether it is getting worse
• your periods: how heavy, how many days, clots and pain
• how it affects work, family and daily life
• diet, medicines and supplements

Ferritin and haemoglobin: why both matter

• Haemoglobin is the oxygen-carrying protein in your blood. A low level means anaemia.
• Ferritin shows your iron stores. Your stores can run low before your haemoglobin drops, so you can be iron deficient without being anaemic.
• A normal blood count does not rule out iron deficiency. One Scottish NHS guide says ferritin is usually the main test.
• Ferritin can be raised by inflammation or infection, even if your iron is low. So your doctor may also check CRP, a marker of inflammation.

"Normal range" is not the same everywhere

Labs and areas use different ferritin cut-offs. Some flag a woman as low only below 15 µg/L, while other NHS guidance treats below 30 as iron depletion. The system is being debated, and a US haematology guideline in 2026 raised its cut-off to 30. If your result is "normal" and you still have symptoms, ask what range the lab used and what your number was.

Tests to ask about

• A full blood count, including haemoglobin
• A ferritin test
• A CRP test, if your ferritin is normal but you are still concerned
• Thyroid function tests (TSH and T4). An underactive thyroid can cause tiredness and hair loss too, so it is worth ruling out.
• A FIT test (faecal immunochemical test). The NHS says that if the cause of iron deficiency is unclear, your GP may order a FIT test to look for hidden blood in your poo, to check your gut. Blood loss from the gut is another common cause.
• To see the actual numbers and the lab's range

Questions to ask

• What were my ferritin and haemoglobin results, and what range does this lab use?
• Could my symptoms still be linked to low iron if the result is in range?
• Should my thyroid be checked too?
• What could be causing low iron in my case, and should that be investigated, including my gut?
• If I need treatment, how long for, and when will I be retested?

How to absorb more iron

• Two kinds of iron: haem iron (red meat, poultry, fish) and non-haem iron (beans, lentils, nuts, dried fruit, dark green leafy vegetables, fortified cereals). Your body absorbs haem iron more easily.
• To boost absorption: eat vitamin C with your meals, such as citrus, peppers or berries. For tablets, the NHS suggests orange juice after the tablet.
• To limit absorption: the NHS says large amounts of tea, coffee, milk and dairy, and foods high in phytic acid such as wholegrain cereals, make it harder to absorb iron. Some people leave a gap between these and iron-rich meals.
• Tablets: speak to your GP or pharmacist first. The NHS says treatment usually lasts about 6 months, and your GP may repeat blood tests to check progress. Supplements of 17mg or less a day are unlikely to cause harm. Keep them away from children.

Sources

NHS: Iron deficiency anaemia · NHS: Symptoms · NHS: Treatment · NHS: Iron · NHS: Underactive thyroid · RUH Bath: Ferritin guide for GPs · NHS Highland: Iron deficiency · UK Parliament petition: Review NHS guidance on iron deficiency for women · News-Medical: ASH 2026 guideline · NICE CKS: Anaemia, iron deficiency

BioHer provides educational information only. It is not medical advice, diagnosis or treatment, and it does not replace your GP or other healthcare professional. If symptoms feel urgent or severe, call 111 for urgent advice, or 999 in an emergency.