Ferritin reflects how much iron your body has in storage. A ferritin below about 15 µg/L (the same number in ng/mL) is a reliable sign of iron deficiency, and many doctors consider values under 30 low enough to suggest depleted stores. Ferritin often falls months before haemoglobin does, so you can have low ferritin with a perfectly normal blood count.
| Category | Reference range |
|---|---|
| Iron deficiency, clear | below 15 µg/L (UK) = ng/mL (US) |
| Iron deficiency likely | 15–30 µg/L (UK) = ng/mL (US) |
| Typical range, women | about 15–150 µg/L (UK) = ng/mL (US) |
| Typical range, men | about 30–400 µg/L (UK) = ng/mL (US) |
µg/L and ng/mL are identical units, so the number does not change. Ranges vary between labs; use the one on your report.
Think of ferritin as the level in your iron store cupboard. Iron in the blood (serum iron) is what is currently on the move, and it swings a lot through the day and after meals. Ferritin changes slowly and is the most useful single test of whether the cupboard is running empty.
One caveat works only in one direction: ferritin also rises with inflammation, infection and liver disease. So a low ferritin almost always means low iron stores, but a normal ferritin does not fully rule them out if you also have inflammation. In that case doctors may add transferrin saturation or CRP.
A ferritin of 15 is at the threshold the WHO uses for iron deficiency in adults. A value of 20 is in the grey zone that many UK and US guidelines treat as likely deficiency, particularly with symptoms or low haemoglobin. Some labs print a lower limit of 10 or 13 for women, so 20 can appear unflagged even though your stores are on the low side.
If you are pregnant, planning pregnancy, have heavy periods or donate blood often, your doctor may act at a higher ferritin than for someone without these factors.
This is very common. The body uses up stored iron first and keeps haemoglobin going until stores are nearly empty, so low ferritin with normal haemoglobin is an early stage of iron deficiency, before anaemia. Serum iron can look normal on the day because it varies so much, so ferritin is the more reliable signal.
Some people with low ferritin and normal haemoglobin feel well; others report tiredness, hair shedding or restless legs. Whether to treat at this stage is a decision to make with your doctor.
Low ferritin means iron is being lost, not absorbed, or not taken in. Common causes:
Low ferritin should always be discussed with your GP or doctor so the cause is found, not just the number corrected. Make an urgent appointment, or use NHS 111, urgent care or the emergency room, if you have:
Written using public information from:
No need to decode the numbers yourself: take a photo of the report and the app explains “Low ferritin” and the rest in plain words — what is normal and what deserves attention.
App StoreGoogle PlayWeb versionBelow 15 µg/L (ng/mL) is clear iron deficiency, and many doctors treat values under 30 as likely low stores. Labs print different ranges, so compare with yours.
Yes. It is the early stage of iron deficiency: the stores run down before anaemia develops. It can still cause symptoms such as tiredness.
It is on the low side. Many guidelines treat values under 30 as suggesting iron deficiency, especially with symptoms, heavy periods or pregnancy. Discuss it with your doctor.
Yes. They are equal units, so a ferritin of 25 ng/mL on a US report is 25 µg/L on a UK one.
It is better not to without a conversation with your doctor. The cause needs to be found, especially in men and after the menopause, and the right form and duration depend on your situation.
This material is for general information only. It is not a medical opinion and does not replace a consultation with a doctor. Reference ranges depend on the laboratory and the method — rely on the range printed on your own report. Your doctor makes the final interpretation.
Ponyatno