Ferritin explained: what’s a normal level for women?

What ferritin measures

Ferritin is a protein that stores iron inside your cells. A small amount circulates in your blood, and that amount reflects how much iron you have in reserve.

Here's a simple way to think about it. Haemoglobin, the part of your red blood cells that carries oxygen, is the iron you're using today. Ferritin is the iron in the cupboard.

That difference matters because the cupboard empties first. Your iron stores can run low while your haemoglobin is still in the normal range. So a full blood count on its own can look fine even when your stores are running down.

Why it matters from your mid-30s

Periods are the main way women lose iron. The NHS lists heavy periods and pregnancy as common causes of iron deficiency anaemia.

Perimenopause can bring heavier bleeding for some women, which can make low iron more likely.

After menopause, ferritin tends to rise. In one population study of 2,680 women, ferritin was about three times higher after menopause than before. Once periods stop, low iron is less expected, and UK guidance says it needs its cause looking into (more on that below).

The NHS lists tiredness and lack of energy, shortness of breath, palpitations, pale skin and headaches among the symptoms of iron deficiency anaemia. But tiredness has many possible causes, and low ferritin is only one of them.

What counts as low? It depends who you ask

This is where it gets interesting.

• The World Health Organization defines iron deficiency in women as a ferritin below 15. That cut-off was set by expert opinion.
• Researchers at the US Centers for Disease Control looked at the point where the body starts to struggle to make red blood cells. They found it was around 25, first in US data and then across 12 countries.
• In 2026, the American Society of Hematology published a guideline setting 30 or lower as its threshold for iron deficiency in adults, including people who menstruate. Where inflammation is present, it uses a higher cut-off, because inflammation pushes ferritin up.
• Some haematologists argue the line for women should be 50.

Ferritin cut-offs for iron deficiency used or proposed by different groups. A scientific debate, not targets. Claryty results are shown against our UK laboratory partner's reference range.

These numbers are in micrograms per litre, which is the same as nanograms per millilitre. So a woman could be "in range" by one definition and below the line by another. This is a live scientific debate, not settled advice, and none of these research numbers is a target to aim for.

Your Claryty result is shown against the reference range used by our UK laboratory partner. If your result is near the lower end and you have symptoms, that's a good reason to talk it through with your GP.

Reading ferritin alongside other markers

Ferritin is most useful read with other results, not on its own.

CRP. Ferritin rises with inflammation or infection, whatever your iron stores are doing. CRP is a marker of inflammation, a bit like a smoke alarm: it tells you there's smoke, not where the fire is. If your CRP is raised, your ferritin may look higher than your true stores. That's why both are reported together.

Full blood count. Haemoglobin and the size of your red cells (MCV) show whether low iron is starting to affect how your blood is made.

Iron and transferrin. Transferrin is the protein that carries iron around your body, like a delivery van. Serum iron is what's on the van today, and it changes with meals, supplements and the time of day, so on its own it can mislead. These two markers are in Claryty Complete.

Other things can raise ferritin too, including liver conditions, drinking a lot of alcohol, and some kidney and thyroid conditions. A high result doesn't automatically mean too much iron.

What a ferritin result can't tell you

• Why your ferritin is low or high.
• Whether a symptom, such as tiredness or hair shedding, is caused by iron.
• That your iron is fine, if inflammation is present. An in-range ferritin can hide low stores when CRP is raised.

Low iron is a finding, not the full answer

If your ferritin is below the reference range, the next question is why. For many women in their 30s and 40s, periods are the obvious explanation. But UK guidance says that in about a third of men and postmenopausal women with iron deficiency anaemia there is an underlying cause, most often in the gut. That's why your GP will want to understand the reason, especially if your periods have stopped or you don't have an obvious explanation.

It's also why we'd encourage you not to start iron supplements on your own. Iron can help: in a trial of women with low ferritin but no anaemia, iron reduced tiredness scores more than a placebo. But too much iron isn't good for you, and treating the number without knowing the cause can mean missing something that needs attention. Talk to your GP or pharmacist first.

Iron-rich foods the NHS suggests include dark-green leafy vegetables, fortified cereals and bread, meat, dried fruit and pulses.

Which Claryty tests include ferritin

• Claryty Energy (£135, 27 markers): ferritin, a full blood count, B12, folate, thyroid, HbA1c, CRP, and liver and kidney markers. Built around common causes of tiredness.
• Claryty Complete (£179, 39 markers): ferritin plus iron and transferrin, a full blood count, CRP, and markers for thyroid, vitamins, female hormones, cholesterol, liver and kidneys.

Both use a home finger-prick kit. Samples are analysed by our UK laboratory partner, and results typically arrive 1–2 working days after your sample reaches the lab. Every marker comes with your result, the reference range used, what it measures and what can influence it.

When to speak to your GP

Speak to your GP if you're tired all the time, your periods are heavy, you're short of breath or have palpitations, or a result surprises you. Claryty provides information, not diagnosis.