Iron deficiency and sports: The athlete's anemia. Iron deficiency in athletes is classified into three stages, with the first stage characterized by low ferritin levels, below 35µg/L, without anemia, and normal hemoglobin levels. Additionally, iron is also lost through sweating, urine, intestinal bleeding during exercise, and increased inflammation after intense physical activity. The most common symptoms of iron deficiency in athletes are fatigue, lethargy, and depression. Difficulty in recovering from training, increased shortness of breath during exercise, decreased performance, and potential immune deficiency are also observed.