© 2016 Elsevier Inc. Anemia is an important cause of health loss. We estimated levels and trends of nonfatal anemia burden for 23 distinct etiologies in 188 countries, 20 age groups, and both sexes from 1990 to 2013. All available population-level anemia data were collected and standardized. We estimated mean hemoglobin, prevalence of anemia by severity, quantitative disability owing to anemia, and underlying etiology for each population using the approach of the Global Burden of Disease, Injuries and Risk Factors 2013 Study. Anemia burden is high. Developing countries account for 89% of all anemia-related disability. Iron-deficiency anemia remains the dominant cause of anemia.