The cutoffs, and what changed in 2024
WHO revised its hemoglobin cutoffs in a guideline published in March 2024. For adults, the numbers did not change: the revision modified the threshold for children aged 6 to 23 months and retained the existing cutoff for pregnant women in the second trimester. What is worth knowing is not that the adult numbers moved, but how they were arrived at.
| Population | Anemia below (g/L) | Anemia below (g/dL) |
|---|---|---|
| Adults 15 to 65 years, men | 130 | 13.0 |
| Adults 15 to 65 years, non-pregnant women | 120 | 12.0 |
| Pregnancy, first trimester | 110 | 11.0 |
| Pregnancy, second trimester | 105 | 10.5 |
| Pregnancy, third trimester | 110 | 11.0 |
| Children 12 to 14 years | 120 | 12.0 |
Why one in twenty healthy people is below the line
The guideline explains its own arithmetic, and the explanation changes how you should read a borderline result. The cutoffs are set at the 5th percentile of a healthy reference population. In WHO's words, that choice "implies that 95% of healthy individuals would have a higher hemoglobin value, and 5% of healthy individuals would still have a lower hemoglobin value than the cutoff and be falsely diagnosed as anemic". The panel picked the more sensitive option on purpose, to catch underlying conditions rather than to avoid false alarms.
So a hemoglobin one or two points under the threshold, in a person with no symptoms and no reason to bleed, is a common finding in healthy people and not by itself alarming. A hemoglobin that has fallen 20 points from your own previous results, even if it is still technically inside the range, is the more interesting event. Trends beat thresholds, which is the general rule for almost every number on a blood panel.
How low is low: the severity bands
WHO grades severity against the same cutoffs. The 2024 guideline kept the existing method, noting that the evidence was insufficient to change it.
| Population | No anemia | Mild | Moderate | Severe |
|---|---|---|---|---|
| Men 15 to 65 | 130 g/L or above | 110 to 129 | 80 to 109 | Below 80 |
| Non-pregnant women 15 to 65 | 120 g/L or above | 110 to 119 | 80 to 109 | Below 80 |
The word "mild" is doing a lot of work in that table and deserves a caution. Mild describes the hemoglobin, not the cause. A mild anemia produced by slow bleeding from a colonic tumor is a serious clinical problem wearing a reassuring label. That is precisely why WHO frames anemia as a sign rather than a diagnosis.
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What actually causes a low hemoglobin
WHO groups the causes into a handful of mechanisms, and it is a useful checklist because the commonest explanation differs by who you are.
- Nutrient deficiency. Iron is the most common nutritional cause worldwide. Deficiencies of vitamin B12, folate, vitamin A and riboflavin also produce anemia through their roles in hemoglobin synthesis and red cell production.
- Blood loss. Heavy menstrual bleeding is a leading cause in menstruating women and is systematically under-investigated. Gastrointestinal bleeding, often occult, is the one that most needs excluding in men and in post-menopausal women.
- Inflammation and chronic disease. Long-running inflammation restricts iron availability and blunts red cell production, producing what is called anemia of inflammation.
- Inherited red cell disorders. Thalassaemia traits, sickle cell disorders and other hemoglobin variants are common in some ancestries and are the reason a lifelong mildly low hemoglobin with small red cells is not automatically iron deficiency.
- Infection. Globally, malaria and parasitic infections are major contributors, which matters for travel and migration history.
The number that a normal hemoglobin can hide
Iron deficiency and anemia are not the same condition, and the sequence is what people get wrong. The body draws down its iron stores first; the hemoglobin only falls once those stores are exhausted. There is therefore a long stage in which iron is genuinely depleted, symptoms such as fatigue, breathlessness on exertion, hair shedding and poor exercise tolerance are real, and the hemoglobin is still comfortably normal.
The test that sees this is ferritin, not hemoglobin. Our guide to the ferritin range covers why WHO publishes two deficiency thresholds and why a ferritin sitting inside a lab's printed range can still represent deficiency when inflammation is present. If you have the symptoms and a normal hemoglobin, ferritin is the number to ask for.
Reading your own result properly
Four things make a hemoglobin result interpretable, and most reports give you three of them.
- Your own previous values. A stable lifelong 128 g/L in a man is a different object from a 128 that was 150 last year.
- Mean corpuscular volume, on the same panel. Small red cells point towards iron deficiency or a thalassaemia trait, large ones towards B12 or folate deficiency, alcohol or thyroid disease. It is the single most informative companion number.
- Whether you have a reason to be losing blood. Periods, gastrointestinal symptoms, aspirin or anti-inflammatory use, recent surgery or donation.
- Ferritin. If it was not done, the panel has not answered the commonest question.
Our hemoglobin reference page lists these thresholds with their source and effective date, and the lab result lookup will place a specific value against them.
Frequently asked questions
What is a normal hemoglobin level for a woman?
WHO defines anemia in non-pregnant women aged 15 to 65 as a hemoglobin below 120 g/L, which is 12.0 g/dL. Above that is not anemic by the WHO definition. Pregnancy uses lower thresholds, 110 g/L in the first and third trimesters and 105 g/L in the second, because blood volume expands.
What is a normal hemoglobin level for a man?
Below 130 g/L, or 13.0 g/dL, defines anemia in men aged 15 to 65. There is no published upper limit in the WHO anemia guideline, because it addresses anemia rather than a raised hemoglobin.
Is 11.9 dangerous?
For a non-pregnant woman that is just under the cutoff, and it counts as mild anemia by the WHO bands. On its own it is not dangerous, but it should not be ignored either, because the grade describes the hemoglobin rather than the cause. The right next step is finding out why, usually starting with ferritin and a look at red cell size.
Why is my hemoglobin reported as 135 instead of 13.5?
Two units are in circulation. Most of the world reports grams per liter, so 135 g/L, and the United States reports grams per decilitre, so 13.5 g/dL. Divide the g/L figure by 10 to convert. The clinical meaning is identical.
Can I raise my hemoglobin by eating more iron?
Only if iron deficiency is what lowered it. Iron will not correct anemia caused by B12 deficiency, inflammation, kidney disease or a thalassaemia trait, and taking it without a cause can delay the diagnosis that matters. WHO's own advice pairs iron-rich foods with vitamin C to improve absorption, and separates iron from calcium supplements, tea and coffee, which reduce it.
When to talk with a clinician
See someone promptly for a hemoglobin in the moderate or severe bands, for any low result accompanied by chest pain, breathlessness at rest, fainting or visible blood loss, and for any unexplained drop in a man or a post-menopausal woman, where bleeding from the gut is the possibility that needs excluding. For a borderline result, the questions worth asking are what my ferritin and red cell size were, what the trend looks like against my previous results, and what cause has been established.
