Anemia is a condition in which you don’t have enough healthy red blood cells to carry adequate oxygen to your tissues. Having anemia may make you feel exhausted.

There are many forms of anemia, each with its own cause. Loss of blood is the most common cause of anemia. Anemia can be temporary or long term, and it can range from mild to severe.

See your doctor if you suspect you have anemia because anemia can be a sign of serious illnesses. Treatments for anemia range from taking supplements to undergoing medical procedures. You may be able to prevent some types of anemia by eating a healthy, varied diet.

Anemia symptoms vary depending on the cause of your anemia but may include:

• Fatigue
• Pale skin
• A fast or irregular heartbeat
• Shortness of breath
• Chest pain
• Dizziness
• Cognitive problems
• Cold hands and feet
• Headache

Initially, anemia can be so mild it goes unnoticed. But symptoms increase as anemia worsens.

Some people learn that their hemoglobin is low, which indicates anemia, when they go to donate blood. Low hemoglobin may be a temporary problem remedied by eating more iron-rich foods or taking a multivitamin containing iron. However, it may also be a warning sign of blood loss in your body that may be causing you to be deficient in iron. If you’re told that you can’t donate blood because of low hemoglobin, make an appointment with your doctor.

Anemia occurs when your blood doesn’t have enough red blood cells. This can happen if:

• Your body doesn’t make enough red blood cells
• Bleeding causes you to lose red blood cells more quickly than they can be replaced
• Your body destroys red blood cells

Common types of anemia and their causes include:

• Iron deficiency anemia. Iron deficiency anemia is caused by a shortage of the element 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. This type of anemia is often caused by blood loss, such as from heavy menstrual bleeding, an ulcer, cancer, a polyp somewhere in your digestive system, and prolonged use of aspirin or drugs known as nonsteroidal anti-inflammatory drugs (NSAIDs).
• Vitamin deficiency anemias. In addition to iron, your body needs folate and vitamin B-12 to produce sufficient numbers of healthy red blood cells. A diet lacking in these and other key nutrients can cause decreased red blood cell production. Additionally, some people may eat enough B-12, but their bodies aren’t able to process the vitamin. This can lead to vitamin deficiency anemia.
• Anemia of chronic disease. Certain chronic diseases — such as cancer, HIV/AIDS, rheumatoid arthritis, Crohn’s disease and other chronic inflammatory diseases — can interfere with the production of red blood cells, resulting in chronic anemia. Kidney failure also can cause anemia.
• Aplastic anemia. This very rare life-threatening anemia is caused by a decrease in the bone marrow’s ability to produce red blood cells. Causes of aplastic anemia include infections, drugs and autoimmune diseases.
• Anemias associated with bone marrow disease. A variety of diseases, such as leukemia and myelodysplasia, can cause anemia by affecting blood production in your bone marrow. The effects of these types of cancer and cancer-like disorders vary from a mild alteration in blood production to a complete life-threatening shutdown of the blood-making process. Other cancers of the blood or bone marrow — such as multiple myeloma, myeloproliferative disorders and lymphoma — also 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. Hemolytic anemias can be inherited, or you can develop them later in life.
• Sickle cell anemia. This inherited and sometimes serious anemia 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.
• Other anemias. There are several other rarer forms of anemia, such as thalassemia and anemias caused by defective hemoglobin.

These factors place you at increased risk of anemia:

• A diet lacking in certain vitamins. Choosing a diet that is consistently low in iron, vitamin B-12 and folate increases your risk of anemia.
• Intestinal disorders. Having an intestinal disorder that affects the absorption of nutrients in your small intestine — such as Crohn’s disease and celiac disease — puts you at risk for anemia. Surgical removal of or surgery to the parts of your small intestine where nutrients are absorbed can lead to nutrient deficiencies and anemia.
• In general, women who haven’t experienced menopause have a greater risk of iron deficiency anemia than do men and postmenopausal women. That’s because menstruation causes the loss of red blood cells.
• If you’re pregnant, you’re at an increased risk of iron deficiency anemia because your iron stores have to serve your increased blood volume as well as be a source of hemoglobin for your growing fetus.
• Chronic conditions. For example, if you have cancer, kidney or liver failure or another chronic condition, you may be at risk for what’s called anemia of chronic disease. These conditions can lead to a shortage of red blood cells. Slow, chronic blood loss from an ulcer or other source within your body can deplete your body’s store of iron, leading to iron deficiency anemia.
• Family history. If your family has a history of an inherited anemia, such as sickle cell anemia, you also may be at increased risk for the condition.
• Other factors. A history of certain infections, blood diseases and autoimmune disorders, alcoholism, exposure to toxic chemicals, and the use of some medications can affect red blood cell production and lead to anemia.

Left untreated, anemia can cause numerous complications, such as:

• Severe fatigue. When anemia is severe enough, you may be so tired that you can’t complete everyday tasks. You may be too exhausted to work or play.
• Heart problems. Anemia can lead to a rapid or irregular heartbeat – an arrhythmia. Your heart must pump more blood to compensate for the lack of oxygen in the blood when you’re anemic. This can even lead to congestive heart failure.
• Some inherited anemias, such as sickle cell anemia, can be serious and lead to life-threatening complications. Losing a lot of blood quickly results in acute, severe anemia and can be fatal.

To diagnose anemia, your doctor may recommend:

• Physical exam. During a physical exam, your doctor may listen to your heart and your breathing. Your doctor may also place his or her hands on your abdomen to feel the size of your liver and spleen.
• Complete blood count (CBC). A CBC is used to count the number of blood cells in a sample of your blood. For anemia, your doctor will be interested in the levels of the red blood cells contained in the blood (hematocrit) and the hemoglobin in your blood. Normal adult hematocrit values vary from one medical practice to another but are generally between 38.8 and 50 percent for men and 34.9 and 44.5 percent for women. Normal adult hemoglobin values are generally 13.5 to 17.5 grams per deciliter for men and 12 to 15.5 grams per deciliter for women.
• A test to determine the size and shape of your red blood cells. Some of your red blood cells may also be examined for unusual size, shape and color. Doing so can help pinpoint a diagnosis. For example, in iron deficiency anemia, red blood cells are smaller and paler in color than normal. In vitamin deficiency anemias, red blood cells are enlarged and fewer in number.

If you receive a diagnosis of anemia, your doctor may order additional tests to determine the underlying cause. For example, iron deficiency anemia can result from chronic bleeding of ulcers, benign polyps in the colon, colon cancer, tumors or kidney failure. Your doctor may test for these and other conditions that may be causing the anemia. Occasionally, it may be necessary to study a sample of your bone marrow to diagnose anemia.

Anemia treatment depends on the cause.

• Iron deficiency anemia.This form of anemia is treated with changes in your diet and iron supplements. If the underlying cause of iron deficiency is loss of blood — other than from menstruation — the source of the bleeding must be located and stopped. This may involve surgery.
• Vitamin deficiency anemias. Folic acid and vitamin C deficiency anemias are treated with dietary supplements and increasing these nutrients in your diet. If your digestive system has trouble absorbing vitamin B-12 from the food you eat, you may receive vitamin B-12 injections.
• Anemia of chronic disease. There’s no specific treatment for this type of anemia. Doctors focus on treating the underlying disease. If symptoms become severe, a blood transfusion or injections of synthetic erythropoietin, a hormone normally produced by your kidneys, may help stimulate red blood cell production and ease fatigue.
• Aplastic anemia. Treatment for this anemia may include blood transfusions to boost levels of red blood cells. You may need a bone marrow transplant if your bone marrow is diseased and can’t make healthy blood cells.
• Anemias associated with bone marrow disease. Treatment of these various diseases can range from simple medication to chemotherapy to bone marrow transplantation.
• Hemolytic anemias. Managing hemolytic anemias includes avoiding suspect medications, treating related infections and taking drugs that suppress your immune system, which may be attacking your red blood cells. Short courses of treatment with steroids or immune suppressant medications can help suppress your immune system’s attack on your red blood cells. Depending on the severity of your anemia, a blood transfusion or plasmapheresis may be necessary. Plasmapheresis is a type of blood-filtering procedure. In certain cases, removal of the spleen can be helpful.
• Sickle cell anemia. Treatment for this anemia may include the administration of oxygen, pain-relieving drugs, and oral and intravenous fluids to reduce pain and prevent complications. Doctors may also recommend blood transfusions, folic acid supplements and antibiotics. A bone marrow transplant may be an effective treatment in some circumstances. A cancer drug called hydroxyurea also is used to treat sickle cell anemia.
• This anemia may be treated with blood transfusions, folic acid supplements, removal of the spleen (splenectomy), a bone marrow transplant or a cancer drug.

Many types of anemia can’t be prevented. However, you can help avoid iron deficiency anemia and vitamin deficiency anemias by choosing a diet that includes a variety of vitamins and nutrients, including:

• Iron-rich foods include beef and other meats, beans, lentils, iron-fortified cereals, dark green leafy vegetables, and dried fruit.
• This nutrient, and its synthetic form folic acid, can be found in citrus fruits and juices, bananas, dark green leafy vegetables, legumes and fortified breads, cereals, and pasta.
• Vitamin B-12. This vitamin is found naturally in meat and dairy products. It’s also added to some cereals and soy products, such as soy milk.
• Vitamin C. Foods containing vitamin C — such as citrus fruits, melons and berries — help increase iron absorption.