Hemoglobin levels define anemia: it is diagnosed when hemoglobin falls below a threshold that depends on age, sex and pregnancy. This cutoff is 130 g/L in adult men, 120 g/L in women and 110 g/L in pregnant women during the first trimester. The World Health Organization revised these benchmarks in March 2024, for the first time since 1968. Here are the exact thresholds by age group. You will also see what they mean after 65 and which tests can find the cause of anemia.
In brief – Anemia is a drop in the concentration of hemoglobin in the blood that reduces oxygen delivery to the tissues. Under the WHO guideline published in 2024, it starts when hemoglobin levels fall below 130 g/L (13 g/dL) in men aged 15 to 65 and below 120 g/L in non-pregnant women. In children, the cutoff is 115 g/L between 5 and 11 years and 105 g/L between 6 and 23 months. During pregnancy, it is 110 g/L in the first and third trimesters and 105 g/L in the second. No specific cutoff exists after 65, for lack of data, so the adult values apply. Worldwide, 1.92 billion people were affected in 2021, or 24.3% of the population. A low number is never a complete diagnosis: the cause must always be found, most often iron deficiency.
Anemia: definition and the hemoglobin levels that define it
A doctor diagnoses anemia when the hemoglobin measured in a blood test falls below the 5th percentile of a healthy population of the same age and sex. Hemoglobin is the protein in red blood cells that picks up oxygen in the lungs and releases it in the organs. In France, laboratories report it in g/dL, as do US labs: 12 g/dL equals 120 g/L.
These anemia cutoffs are statistical, not biological. One healthy person in twenty naturally sits below the limit. Conversely, a fall of 20 g/L from your usual value can go unnoticed if you stay above the threshold. Hematologists Ernest Beutler and Jill Waalen showed that the 1968 limits relied on very small samples and ignored age (Beutler and Waalen, 2006).
To update these benchmarks, the WHO commissioned an analysis of eight data sources covering eight countries, from China to Canada. Anyone with a deficiency, inflammation or disease that could lower hemoglobin was excluded (Braat et al., 2024). The table below compares the official cutoffs with the values measured.
| Population | Anemia if hemoglobin is below | 5th percentile measured in healthy people (Braat 2024) |
|---|---|---|
| Children aged 6 to 23 months | 105 g/L (10.5 g/dL) | 104.4 g/L (924 children) |
| Children aged 24 to 59 months | 110 g/L (11 g/dL) | 110.2 g/L (1,874 children) |
| Children aged 5 to 11 years | 115 g/L (11.5 g/dL) | 114.4 g/L (1,839 children) |
| Girls and boys aged 12 to 14 years | 120 g/L (12 g/dL) | 122.2 g/L in girls, 128.2 g/L in boys (12-17 years) |
| Non-pregnant women aged 15 to 65 | 120 g/L (12 g/dL) | 119.7 g/L (3,640 women) |
| Men aged 15 to 65 | 130 g/L (13 g/dL) | 134.9 g/L (2,377 men) |
| Pregnancy, 1st trimester | 110 g/L (11 g/dL) | 110.3 g/L (772 women) |
| Pregnancy, 2nd trimester | 105 g/L (10.5 g/dL) | 105.9 g/L (111 women) |
| Pregnancy, 3rd trimester | 110 g/L (11 g/dL) | Insufficient data |
| Over 65 | Adult cutoffs (130 or 120 g/L) | Insufficient data |
The full guideline, with the adjustments for smoking and altitude, is available on the WHO website: Guideline on haemoglobin cutoffs to define anaemia in individuals and populations. Its authors summarize the reasoning in The Lancet (Pasricha et al., 2024).
Anemia cutoffs: why hemoglobin levels vary with age, sex and pregnancy
Cutoffs are identical for girls and boys until puberty, then diverge under the influence of sex hormones. In adults, average hemoglobin in women is about 12% lower than in men, a gap also found in many mammals, birds and reptiles (Murphy, 2014). Menstrual blood loss adds to this hormonal difference and gradually drains iron stores.
Several factors shift the measured value without reflecting disease:
- Pregnancy, in which plasma volume rises faster than red cell mass, diluting hemoglobin in the second trimester.
- Smoking, which artificially raises hemoglobin: the WHO subtracts 3 g/L in light smokers and up to 6 g/L above 20 cigarettes a day.
- Altitude, which boosts red blood cell production: the adjustment starts at 500 m (about 1,640 ft) and reaches 33 g/L between 4,500 and 4,999 m (about 14,760 to 16,400 ft).
- Dehydration, which concentrates the blood and can mask a real decline.
- Ethnic origin, which the WHO set aside in 2024: no common, clinically silent genetic variant justifies different cutoffs by ancestry.
After 65, the question remains open. The analysis by Braat and colleagues stops at 65 for lack of older healthy participants, so the WHO offers no cutoff specific to seniors. Bone marrow produces fewer cells with age. Yet anemia in an older person more often signals a disease than the simple passage of time.
Anemia and health after 65: what the science says
After 65, anemia is associated with more deaths, hospital stays, loss of independence and dementia, even in its mild form. These data come from observational cohorts. They describe an association, not a proven cause-and-effect relationship.
Prevalence rises sharply with age. In the US NHANES III survey, 11.0% of men and 10.2% of women aged 65 and over were anemic. The proportion exceeded 20% after 85 (Guralnik et al., 2004). Causes split into three thirds: nutritional deficiencies (iron, folate, vitamin B12), chronic inflammation or kidney disease, and unexplained anemia. Most cases were mild: only 2.8% of women and 1.6% of men had hemoglobin below 110 g/L.
The measured consequences are specific:
- In the Cardiovascular Health Study (5,888 people aged 65 and over, followed for 11.2 years), anemia was associated with a 38% higher risk of death after full adjustment (Zakai et al., 2005).
- Among 17,030 Canadians aged 66 and over, hemoglobin below 110 g/L multiplied the risk of death by 4.29; the lowest mortality was between 130 and 150 g/L in women and between 140 and 170 g/L in men (Culleton et al., 2006).
- Among 1,146 people aged 71 and over, physical performance (balance, walking, rising from a chair) fell by 2.3 points over 4 years with anemia, versus 1.4 points without (Penninx et al., 2003).
- In the Health ABC study (2,552 participants, mean age 76), 23% of people with anemia developed dementia over 11 years, compared with 17% of the others (Hong et al., 2013).
This work fuels a debate about the cutoffs. Among 755 residents of Leiden aged 85 and over, the WHO cutoffs did identify excess mortality. The risk of death was multiplied by 1.60 in women with anemia and by 2.29 in men (Izaks et al., 1999). In contrast, the Penninx study observed faster physical decline from “borderline anemia” onward, up to 10 g/L above the cutoff. For prevention, the trend in hemoglobin levels from one blood test to the next matters as much as a single value.
In practice: reading your blood test and finding the cause
When facing anemia, the first step is to check the mean corpuscular volume (MCV), which points toward the cause within seconds. This value appears on every complete blood count (CBC). It measures the average size of red blood cells.
| Type | MCV | Most common causes | Useful tests |
|---|---|---|---|
| Microcytic | Below 80 fL | Iron deficiency (heavy periods, digestive bleeding), thalassemia | Ferritin, CRP, search for bleeding |
| Normocytic | 80 to 100 fL | Chronic inflammation, kidney disease, recent blood loss, bone marrow origin | CRP, creatinine, reticulocytes |
| Macrocytic | Above 100 fL | Vitamin B12 or folate deficiency, alcohol, hypothyroidism, certain medications | Vitamin B12, folate, TSH |
Iron deficiency remains the leading cause of anemia worldwide. According to the Global Burden of Disease, it outweighed all other causes combined in years lived with disability in 2021 (GBD 2021 Anaemia Collaborators, 2023). Ferritin is the key marker, but inflammation raises it and can hide a real shortfall. Our article on low or high ferritin explains how to interpret it. In a man or a postmenopausal woman, iron deficiency calls for a search for digestive bleeding (Camaschella, 2015).
Anemia of inflammation accompanies infections, autoimmune diseases, cancers and kidney failure. Hepcidin, a liver hormone, blocks the use of iron: the iron is present but unavailable (Weiss and Goodnough, 2005). Oversized red blood cells point to anemia from a lack of vitamin B12, common after 60, in vegans and in people taking metformin or proton pump inhibitors (Stabler, 2013). Signs and doses are covered in our guide to vitamin B12 deficiency.
Severity can also be read in numbers. In adults, the WHO defines mild anemia as 110 to 119 g/L in women and 110 to 129 g/L in men. It becomes moderate between 80 and 109 g/L, then severe below 80 g/L.
| Level | Non-pregnant woman | Man | Usual course of action |
|---|---|---|---|
| Normal | 120 g/L and above | 130 g/L and above | Track the trend at routine checkups |
| Mild | 110 to 119 g/L | 110 to 129 g/L | Workup for the cause with your primary care doctor |
| Moderate | 80 to 109 g/L | 80 to 109 g/L | Prompt workup, search for bleeding |
| Severe | Below 80 g/L | Below 80 g/L | Medical advice the same day |
After 65, hemoglobin levels that drop without explanation may also reflect aging of the blood stem cells; this mechanism is explained in our pillar page on stem cell exhaustion and in our article on bone marrow aging.
Anemia: tips to monitor your hemoglobin levels and prevent it
The most useful prevention is to know your baseline value and to act on the cause, never to take iron blindly. An iron supplement taken without a diagnosis can mask digestive bleeding. In people with hemochromatosis, it can also worsen iron overload.
- Keep your CBC results to compare from year to year: a fall of more than 10 g/L deserves an explanation, even above the cutoff.
- Ask for ferritin and CRP together, since inflammation distorts the reading of iron stores.
- Pair a source of vitamin C with foods rich in non-heme iron (lentils, chickpeas, spinach) and keep tea and coffee away from meals.
- After 60, if you take metformin or follow a vegan diet, have your vitamin B12 and folate checked.
- Women with heavy periods: mention it, because it is the leading cause of iron deficiency before menopause.
- Smokers and people living at altitude: remind your doctor, since both situations raise hemoglobin and can hide anemia.
The WHO lists the most common symptoms of anemia: fatigue, dizziness, cold hands and feet, headaches and shortness of breath on exertion. Severe forms add pale mucous membranes and a rapid pulse (WHO fact sheet on anaemia). To receive our summaries on blood markers and healthy aging, subscribe to our health newsletter.
Frequently asked questions about anemia and hemoglobin levels
What are normal hemoglobin levels for women?
In non-pregnant women aged 15 to 65, hemoglobin is considered normal from 120 g/L, or 12 g/dL. The cutoff drops to 110 g/L in the first and third trimesters of pregnancy and to 105 g/L in the second. In the data pooled for the WHO in 2024, the 5th percentile of 3,640 healthy women was 119.7 g/L.
At what hemoglobin level is a man considered anemic?
In men aged 15 to 65, anemia starts below 130 g/L (13 g/dL). It is called mild between 110 and 129 g/L, moderate between 80 and 109 g/L and severe below 80 g/L. Iron deficiency in a man calls for a search for blood loss, most often digestive, even without symptoms.
Do hemoglobin levels normally fall with age?
A slight decline is common, but it is not considered normal. The WHO has set no cutoff specific to people over 65 for lack of data and applies the adult values. In the NHANES III survey, one third of the cases seen after 65 stemmed from a nutritional deficiency and one third from inflammation or kidney disease: a cause can therefore often be identified.
What is the difference between anemia and iron deficiency?
Anemia means hemoglobin that is too low, whatever the cause. Iron deficiency is the depletion of iron stores, detected by low ferritin, and it can exist long before hemoglobin falls. It is the most common cause of anemia worldwide, but not the only one: inflammation, kidney disease and lack of vitamin B12 are others.
When should anemia prompt an urgent medical visit?
Same-day medical advice is needed for hemoglobin below 80 g/L, black stools or blood in the stools, shortness of breath at rest, chest pain or fainting. A rapid drop between two blood tests, unexplained weight loss or worsening fatigue also justify a workup without waiting for the next checkup.
Medical disclaimer. The information on this page is provided for informational purposes only and does not constitute medical advice. It does not replace a consultation. Ask a healthcare professional before changing your diet, taking dietary supplements or starting a new practice, especially if you have a medical condition, are pregnant or are under treatment. Dietary supplements do not replace a balanced diet or medical follow-up.
