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Percentage of women aged 15−49 years with a haemoglobin concentration less than 120 g/L for non-pregnant women and lactating women, and less than 110 g/L for pregnant women, adjusted for altitude and smoking.
Anaemia severity levels:- For total anaemia: Percentage of women aged 15−49 years with a haemoglobin concentration less than 120 g/L for non-pregnant women and lactating women, and less than 110 g/L for pregnant women, adjusted for altitude and smoking.
- For mild anaemia: Percentage of women aged 15−49 years with a haemoglobin concentration between 110-119 g/L for non-pregnant women and lactating women, and between 100-109 g/L for pregnant women, adjusted for altitude and smoking.
- For moderate anaemia: Percentage of women aged 15−49 years with a haemoglobin concentration between 80-109 g/L for non-pregnant women and lactating women, and between 70-99 g/L for pregnant women, adjusted for altitude and smoking.
- For severe anaemia: Percentage of women aged 15−49 years with a haemoglobin concentration less than 80 g/L for non-pregnant women and lactating women, and less than 70 g/L for pregnant women, adjusted for altitude and smoking.
Prevalence of anaemia and/or mean haemoglobin in women of reproductive age were obtained from 412 population-representative data sources from 122 countries worldwide. Data collected from the years 1995 to 2023 were used. Adjustment of data on blood haemoglobin concentrations for altitude and smoking was carried out whenever possible. Biologically implausible haemoglobin values (<25 g/L or >200 g/L) were excluded. A Bayesian hierarchical mixture model was used to estimate haemoglobin distributions and systematically addressed missing data, non-linear time trends, and representativeness of data sources. Based on the latest evidence, the use of venous blood was recommended as the gold standard for measuring haemoglobin concentrations due to its high accuracy. However, thus far, national survey data based on venous blood are limited compared to capillary blood. For the current exercise, we accounted for possible higher error in haemoglobin measurements using capillary blood by taking only the mean haemoglobin concentrations because means are not affected by higher measurement errors. We used all available summary statistics or individual-level data if assessment was done using venous blood. We also allowed for suspected biased measurements by measurement method when using HemoCue® 301. These enhancements were applied considering the emerging evidence on measurement errors in haemoglobin that can influence the accuracy and precision of estimates.
Full details on statistical methods may be found here: National, regional, and global estimates of anaemia by severity in women and children for 2000–19: a pooled analysis of population-representative data (Stevens et al, 2022).
Prevalence of anaemia by severity level at global level Only the prevalence by severity levels at the global level are being published due to the nature of the primary data sources used. Because of variability in measurement methods, mean haemoglobin concentrations were used for capillary blood, whereas full statistical distributions were available for primary sources using venous blood. In addition, only a few primary sources collected venous blood in high-prevalence regions. As a result, the severity levels have inherent limitations compared with total anaemia estimates at the country level, where mean haemoglobin values are often close to the threshold for total anaemia in high-prevalence regions.