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 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 over 15 years)
- Hb <13 g/dL in adult males (ages over 15 years)
- 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 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.
Globally, in 2019, 40% of children ages 6 to 59 months were anemic.[7] Africa and South-East Asia are the most affected regions. For all population groups combined, the Global Burden of Disease Study (2019) estimated that approximately 23% of the world's population had some form of anemia, affecting 1.8 billion people.[8]
