Our body needs oxygen to survive, and our blood helps oxygen get to all parts of the body.  When you don't have enough of a component of the blood called red blood cells or hemoglobin, this is called anemia, a common condition that affects millions of people worldwide. Some patients only find out they have anemia when they have routine tests done on an annual examination, in preparation for surgery or before donating blood.

There are a few different reasons for having anemia. A common reason is not having enough iron. This is called iron deficiency anemia and can happen when:

1. You have lost a large amount of blood. This can happen slowly over time or all of a sudden. It is the most common cause of iron deficiency anemia. Menstrual periods and pregnancy are common reasons. Bleeding can also come from tumors in the intestines or colon which bleed slowly and in small amounts, so it is not noticeable in your bowel movements.
2. Your body cannot absorb enough iron from food. This can happen in conditions like celiac disease or after surgery of your stomach or intestines. Some medications can also interfere with iron absorption.
3. You do not get enough iron in your food. This can happen if infants or those on restrictive diets do not get enough iron from food or supplements. Vegetarians who eliminate meat can develop iron deficiency anemia.

Other causes of anemia are:

1. Deficiency in vitamins like B12 and folate
2. Inherited causes — Thalassemia, sickle cell anemia
3. Aplastic anemia — A rare condition where the body stops producing enough new blood cells
4. Hemolytic anemia — Where red blood cells are destroyed faster than they can be produced
5. Chronic kidney disease — This can affect how red blood cells are made.

Patients with anemia sometimes do not have any symptoms when the anemia is mild or when they have had it for a long time as a chronic illness. Those who do have symptoms might have the following: