Mild, moderate, and severe anemia according to WHO.
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WHO anemia classification mild moderate severe hemoglobin thresholds 2023
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https://www.who.int/news-room/fact-sheets/detail/anaemia
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https://iris.who.int/bitstreams/77138c76-cea1-4459-bc49-c596…
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I now have enough information from authoritative sources. Here is the complete WHO classification of anemia severity.
WHO Classification of Anemia by Severity
The WHO defines anemia based on hemoglobin (Hb) concentrations that fall below established thresholds, which vary by age, sex, and physiological status (especially pregnancy). Severity is then graded within each group.
Diagnostic Thresholds (Hb below which = anemia)
| Population Group | Hb Threshold for Anemia |
|---|---|
| Children 6 months - 4 years | < 11.0 g/dL |
| Children 5 - 11 years | < 11.5 g/dL |
| Children 12 - 14 years | < 12.0 g/dL |
| Non-pregnant women ≥15 years | < 12.0 g/dL |
| Pregnant women | < 11.0 g/dL |
| Men ≥15 years | < 13.0 g/dL |
Severity Classification by Hb (g/dL)
Non-pregnant Women & General Adults
| Severity | Hb (g/dL) |
|---|---|
| Mild | 11.0 - 11.9 (women) / 11.0 - 12.9 (men) |
| Moderate | 8.0 - 10.9 |
| Severe | < 8.0 |
Pregnant Women
| Severity | Hb (g/dL) |
|---|---|
| Mild | 10.0 - 10.9 |
| Moderate | 7.0 - 9.9 |
| Severe | < 7.0 |
Children (6 months - 5 years)
| Severity | Hb (g/dL) |
|---|---|
| Mild | 10.0 - 10.9 |
| Moderate | 7.0 - 9.9 |
| Severe | < 7.0 |
Key Notes
- Severe anemia is clinically the most important category - Hb < 7 g/dL in most groups carries a significantly elevated risk of maternal and child mortality, as well as end-organ compromise.
- Anemia of pregnancy is defined by WHO as Hb < 11 g/dL (any trimester), slightly stricter than the non-pregnant female threshold.
- Men have a higher normal Hb range, so "mild" anemia in men spans a wider Hb band (11.0-12.9 g/dL) compared to women.
- The Tietz Textbook of Laboratory Medicine confirms: WHO defines anemia as Hb < 13 g/dL in adult men and < 12 g/dL in adult nonpregnant women at sea level.
- Some textbooks use a slightly simplified rule of thumb: Hb ≥ 9.5 = mild; 8.0-9.4 = moderate; < 8.0 = severe (Frameworks for Internal Medicine, p. 328).
- Altitude correction applies: at high altitudes, Hb thresholds are adjusted upward because normal Hb is physiologically higher.
Public Health Severity (Population Level)
WHO also classifies anemia as a public health problem by population prevalence:
| Prevalence in a population | Public health category |
|---|---|
| < 5% | Not a public health problem |
| 5 - 19.9% | Mild |
| 20 - 39.9% | Moderate |
| ≥ 40% | Severe |
This is separate from individual clinical severity and is used for epidemiological surveillance and program planning.
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