The symptoms of anemia include fatigue, weakness, pale skin, shortness of breath, lightheadedness, dizziness, and rapid or irregular heartbeat. Anemia officially occurs when hemoglobin concentrations drop below two standard deviations of the mean for the average healthy population of the same age, gender, and altitude (the decreased oxygen levels in high-altitude air can affect iron metabolism!) Anemia can be caused by iron deficiency, but additionally deficiencies in B vitamins can cause differ