Anemia is a hemoglobin (Hb) level two standard deviations below the mean for the age and sex of the patient. Reference ranges vary between laboratories. The World Health Organization (WHO) recommends the following hemoglobin cutoffs to define anemia in the individual:[1]
- Hb <10.5 g/dL in children ages 6 to 23 months
- Hb <11 g/dL in children ages 24 to 59 months
- Hb <11.5 g/dL children ages 5 to 11 years
- Hb <12 g/dL in children ages 12 to 14 years
- Hb <12 g/dL in nonpregnant adult females (ages 15 years and over)
- Hb <13 g/dL in adult males (ages 15 years and over)
- Hb <11 g/dL during the first trimester pregnancy
- Hb <10.5 g/dL during the second trimester pregnancy
- Hb <11 g/dL during the third trimester pregnancy
Adjustments to hemoglobin cut-off values may be required, according to external factors, such as cigarette smoking and the population's elevation above sea level.[1]
Anemia is commonly seen in general medical practice.[2] [3] Risk factors include extremes of age, female sex, lactation, and pregnancy. The most common cause of anemia globally is dietary iron deficiency.[4] [5]
Anemia can cause significant morbidity if left untreated, and is often the presenting sign of a more serious underlying condition.[6] The rate at which anemia develops is often as important as the severity, as a rapid decline can overwhelm the compensatory mechanisms of the body.
For all population groups combined, the Global Burden of Disease Study (2021) estimated that approximately 24% of the world's population had some form of anemia, affecting 1.9 billion people.[5] Sub-Saharan Africa and South Asia are particularly affected.[5]
The WHO estimated that 30.7% of women of reproductive age were anemic in 2023, with the highest prevalence in South-East Asia and Africa.[7]
Globally, in 2019, 40% of children ages 6-59 months were anemic.[8]
