Anemia

If you have anemia, people may say you have tired blood. That's because anemia — a condition in which there aren't enough healthy red blood cells to carry adequate oxygen to your tissues — can make you feel tired.

Many types of anemia exist, each with its own cause. The cause may be an iron or vitamin deficiency, blood loss, a chronic illness, or a genetic or acquired defect or disease. It may also be a side effect of a medication. Anemia can be temporary or long-term. It can range from mild to severe.

Anemia affects 3.4 million Americans, making it the most common blood disorder in the United States. Women and people with chronic diseases are at increased risk of the condition.

If you suspect you have anemia, see your doctor. Anemia can be a sign of serious illnesses, such as cancer or kidney disease. Treatments for anemia range from taking vitamin and iron supplements to undergoing medical procedures, such as blood transfusions or surgery. You may prevent some types of anemia by eating a healthy, varied diet.

The main symptom of most types of anemia is fatigue. Other signs and symptoms of anemia include:

• Weakness
• Pale skin, including decreased pinkness of your lips, gums, lining of your eyelids, nail beds and palms
• A rapid heartbeat
• Shortness of breath
• Chest pain
• Dizziness
• Irritability
• Numbness or coldness in your hands and feet
• Headache

Initially, anemia can be so mild it goes unnoticed. But signs and symptoms increase as the condition progresses.

Blood consists of both a liquid called plasma and cells. Floating within the plasma are three types of blood cells:

• White blood cells. These blood cells fight infection.
• Platelets. These blood cells help your blood clot after a cut.
• Red blood cells (erythrocytes). These are the most abundant of the three types. They carry oxygen from your lungs, via your bloodstream, to your brain and the other organs and tissues. Your body needs a supply of oxygenated blood to function. Oxygenated blood helps give your body its energy and your skin a healthy glow.

Red blood cells contain hemoglobin — a red, iron-rich protein that gives blood its red color. Hemoglobin enables red blood cells to carry oxygen from your lungs to all parts of your body, and to carry carbon dioxide waste from other parts of the body to the lungs so that it can be exhaled.

Most blood cells, including red blood cells, are produced regularly in your bone marrow — a red, spongy material found within the cavities of many of your large bones. To produce hemoglobin and red blood cells, your body needs iron and vitamins from the foods you eat.

Anemia is a state in which the number of red blood cells or the hemoglobin in them is below normal. When you're anemic, your body produces too few healthy red blood cells, loses too many of them or destroys them faster than they can be replaced. As a result, your blood is low on red blood cells to carry oxygen to your tissues — leaving you fatigued. Common types of anemia and their causes include:

• Iron deficiency anemia. This most common form of anemia affects 20 percent of women, 50 percent of pregnant women and 3 percent of men in the United States. The cause is a shortage of the mineral iron in your body. Your bone marrow needs iron to make hemoglobin. Without adequate iron, your body can't produce enough hemoglobin for red blood cells. The result is iron deficiency anemia. One way your body gets iron is when blood cells die — the iron in them is recycled and used to produce new blood cells. So, if you lose blood, you lose iron. Women with heavy periods who lose a lot of blood each month during menstruation are at risk of iron deficiency anemia. Slow, chronic blood loss from a source within the body — such as an ulcer, a colon polyp or even colon cancer — also can lead to iron loss and iron deficiency anemia. Your body also gets iron from the foods you eat. An iron-poor diet can lead to this anemia. In pregnant women, a growing fetus can deplete the mother's store of iron, leading to iron deficiency anemia.

• Vitamin deficiency anemias. In addition to iron, your body needs folate and vitamin B-12 to produce sufficient numbers of healthy red blood cells. Dietary requirements of folate are much greater than are those for vitamin B-12. A diet lacking in these and other key nutrients can cause decreased red blood cell production. People who have an intestinal disorder that affects the absorption of nutrients are prone to this type of anemia. Some people are unable to absorb vitamin B-12 for a variety of reasons and develop vitamin B-12 deficiency anemia, which is also known as pernicious anemia. Vitamin deficiency anemias fall into a group of anemias called megaloblastic anemias, in which the bone marrow produces large, abnormal red blood cells called megaloblasts. Vitamin deficiency anemias can be related to the use of certain medications, such as oral contraceptives, antiseizure medications and drugs used to treat cancer.

• Anemia of chronic disease. Certain chronic diseases — such as AIDS, cancer, liver disease and chronic inflammatory diseases, such as rheumatoid arthritis — can interfere with the production of red blood cells, resulting in chronic anemia. Kidney failure also can be a cause of anemia. The kidneys produce a hormone called erythropoietin, which stimulates your bone marrow to produce red blood cells. A shortage of erythropoietin, which can result from kidney failure or be a side effect of chemotherapy, can result in a shortage of red blood cells.

• Aplastic anemia. This is a life-threatening anemia caused by a decrease in the bone marrow's ability to produce all three types of blood cells — red blood cells, white blood cells and platelets. Often, the cause of aplastic anemia is unknown, but it's believed to be an autoimmune disease. Some factors that can be responsible for this type of anemia include chemotherapy, radiation therapy, environmental toxins, pregnancy and lupus.

• Anemias associated with bone marrow disease. A variety of diseases, such as leukemia and myelodysplasia, can cause anemia by affecting blood production in the bone marrow. The effects of these types of cancer and cancer-like disorders vary from a mild alteration in blood production to a complete shutdown of the blood-making process. The aggressive (acute) form of leukemia can be fatal because it causes such a dramatic drop in the production of blood cells. Myelodysplasia is a preleukemic condition that can cause anemia. Additionally, other cancers of the blood or bone marrow, such as multiple myeloma or lymphoma, can cause anemia.

• Hemolytic anemias. This group of anemias develops when red blood cells are destroyed faster than bone marrow can replace them. Certain blood diseases can cause increased red blood cell destruction. Autoimmune disorders can cause your body to produce antibodies to red blood cells, destroying them prematurely. Certain medications, such as some antibiotics used to treat infections, also can break down red blood cells. Hemolytic anemias may cause yellowing of the skin (jaundice) and an enlarged spleen.
• Sickle cell anemia. This inherited and sometimes serious anemia, which affects mainly people of African and Arabic descent, is caused by a defective form of hemoglobin that forces red blood cells to assume an abnormal crescent (sickle) shape. These irregular-shaped red blood cells die prematurely, resulting in a chronic shortage of red blood cells. Sickle-shaped red blood cells also can block blood flow through small blood vessels in the body, producing other, often painful, symptoms.

• Other anemias. There are several other, rarer forms of anemia, such as thalassemia and anemias caused by defective hemoglobin.

Sometimes, no cause of anemia can be identified.