Hemoglobin deficiency, also known as anemia, is a condition in which there is not enough hemoglobin in the blood. Hemoglobin is a protein found in red blood cells that carries oxygen from the lungs to the rest of the body. When there is not enough hemoglobin in the blood, the body's tissues and organs do not get enough oxygen, which can lead to symptoms such as fatigue, weakness, and shortness of breath. Anemia can be caused by a variety of factors, including blood loss, poor nutrition, and certain medical conditions. It is typically treated with a combination of lifestyle changes, such as eating a healthy diet and exercising regularly, and medications such as iron supplements.