Anemia
The most noticeable outward symptom of anemia is usually pallor of the skin, mucous membranes, and nail beds. Symptoms of tissue oxygen deficiency include pulsating noises in the ear, dizziness, fainting, and shortness of breath.In anemia your blood has a lowered ability to carry oxygen, which can be caused by various reasons (e.g. blood loss, increased red blood cell breakdown, decreased red blood cell production - including iron deficiency, vitamin B12 deficiency, and many others).