Hemoglobin (haemoglobin in UK spelling) is low, or you have anaemia, when it is below about 120 g/L (12.0 g/dL) in women and 130 g/L (13.0 g/dL) in men, the World Health Organization thresholds that most labs use. UK reports give g/L, US reports g/dL: 110 g/L and 11.0 g/dL are the same number. The most common cause, especially in women, is iron deficiency.
| Category | Reference range |
|---|---|
| Women, not pregnant | 120–150 g/L / 12.0–15.0 g/dL g/L (UK) / g/dL (US) |
| Men | 130–170 g/L / 13.0–17.0 g/dL g/L (UK) / g/dL (US) |
| Pregnancy, anaemia threshold | below 110 g/L / 11.0 g/dL (first trimester), below 105 g/L later g/L (UK) / g/dL (US) |
| Mild anaemia, women | 110–119 g/L / 11.0–11.9 g/dL g/L (UK) / g/dL (US) |
| Severe anaemia, adults | below 80 g/L / 8.0 g/dL g/L (UK) / g/dL (US) |
Ranges vary between labs and with altitude and ethnicity; use the range on your report. To convert, g/L ÷ 10 = g/dL.
Women normally have lower haemoglobin than men because of monthly blood loss and hormonal differences. That is why a value of 125 g/L is normal for a woman but low for a man. Children's ranges depend on age, and in pregnancy haemoglobin naturally falls a little as blood volume expands.
Smoking and living at high altitude raise haemoglobin, so labs and doctors take them into account. Some people of African heritage also run slightly lower values without any illness.
For a non-pregnant woman, 110 g/L (11.0 g/dL) is mild anaemia; for a man it is moderate. In early pregnancy it sits right at the threshold. Many people at this level feel only somewhat more tired than usual, or nothing at all, especially if it has developed slowly.
The number becomes more significant when it has dropped quickly, when it keeps falling, or when it is below about 80–90 g/L (8–9 g/dL). The speed of change matters as much as the value: a fall from 140 to 115 over a few months deserves more attention than a stable 115 for years.
The full blood count already gives clues. MCV, the average size of red cells, splits anaemia into three broad groups: small cells (often iron), normal-sized cells (chronic disease, blood loss, kidney disease) and large cells (B12, folate, alcohol, thyroid). Next come ferritin for iron stores, B12 and folate, kidney function and sometimes reticulocytes and a blood film.
In men and in women after the menopause, iron-deficiency anaemia without an obvious cause is usually investigated for bleeding from the gut, which in the UK often means a referral for tests of the stomach and bowel. This is routine practice, not a sign that something serious has been found.
Any result below your lab's range should be discussed with your GP or doctor, who will find the cause before any treatment. Seek urgent care (A&E, the emergency room, NHS 111 or 999/911) if you have low haemoglobin and:
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No need to decode the numbers yourself: take a photo of the report and the app explains “Low hemoglobin” and the rest in plain words — what is normal and what deserves attention.
App StoreGoogle PlayWeb versionRoughly 120 to 150 g/L, or 12.0 to 15.0 g/dL. Below 120 g/L is classed as anaemia in non-pregnant women by the WHO. In pregnancy the threshold is lower.
Yes. For a non-pregnant woman it is mild anaemia, and for a man it is moderate. The cause, often iron deficiency, needs to be found by your doctor.
There is no single cut-off, but values under about 70 to 80 g/L (7 to 8 g/dL), a sudden fall, or low haemoglobin with chest pain, breathlessness or fainting need urgent medical attention.
They measure related things: haemoglobin is the oxygen-carrying protein, haematocrit the share of blood made up of red cells. When one is low the other usually is too, and both point to anaemia.
Not without checking with your doctor. Not all anaemia is caused by iron deficiency, iron can be harmful in some conditions, and starting it before tests can hide a cause such as bleeding.
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.
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