Anemia signs and symptoms vary depending on the cause of your anemia. They may include:

• Fatigue

• Weakness

• Pale or yellowish skin

• Irregular heartbeats

• Shortness of breath

• Dizziness or lightheadedness

• Chest pain

• Cold hands and feet

• Headache

At first anemia can be so mild that it goes unnoticed. But symptoms worsen as anemia worsens.

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

Causes of anemia

Different types of anemia and their causes include:

• Iron deficiency anemia. This is the most common type of anemia worldwide. Iron deficiency anemia is caused by a shortage of 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.

Without iron supplementation, this type of anemia occurs in many pregnant women. It is also caused by blood loss, such as from heavy menstrual bleeding, an ulcer, cancer and regular use of some over-the-counter pain relievers, especially aspirin.

• Vitamin deficiency anemia. In addition to iron, your body needs folate and vitamin B-12 to produce enough healthy red blood cells. A diet lacking in these and other key nutrients can cause decreased red blood cell production.

Additionally, some people may consume enough B-12, but their bodies aren't able to process the vitamin. This can lead to vitamin deficiency anemia, also known as pernicious anemia.

• Anemia of chronic disease. Certain diseases — such as cancer, HIV/AIDS, rheumatoid arthritis, kidney disease, Crohn's disease and other chronic inflammatory diseases — can interfere with the production of red blood cells.

• Aplastic anemia. This rare, life-threatening anemia occurs when your body doesn't produce enough red blood cells. Causes of aplastic anemia include infections, certain medicines, autoimmune diseases and exposure to toxic chemicals.

• Anemias associated with bone marrow disease. A variety of diseases, such as leukemia and myelofibrosis, can cause anemia by affecting blood production in your bone marrow. The effects of these types of cancer and cancer-like disorders vary from mild to life-threatening.

• Hemolytic anemias. This group of anemias develops when red blood cells are destroyed faster than bone marrow can replace them. Certain blood diseases increase red blood cell destruction. You can inherit a hemolytic anemia, or you can develop it later in life.

• Sickle cell anemia. This inherited and sometimes serious condition is an inherited hemolytic anemia. It's caused by a defective form of hemoglobin that forces red blood cells to assume an abnormal crescent (sickle) shape. These irregular blood cells die prematurely, resulting in a chronic shortage of red blood cells.

• Other anemias. There are several other forms of anemia, such as thalassemia and malarial anemia.

These factors place you at increased risk of anemia:

• A diet lacking in certain vitamins. Having 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 of anemia.

• Menstruation. 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.

• Pregnancy. If you're pregnant and aren't taking a multivitamin with folic acid, you're at an increased risk of anemia.

• Chronic conditions. If you have cancer, kidney failure or another chronic condition, you may be at risk of 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 of 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.

• Age. People over age 65 are at increased risk of anemia.

Left untreated, anemia can cause many health problems, such as:

• Severe fatigue. When anemia is severe enough, you may be so tired that you can't complete everyday tasks.

• Pregnancy complications. Pregnant women with folate deficiency anemia may be more likely to experience complications, such as premature birth.

• Heart problems. Anemia can lead to a rapid or irregular heartbeat (arrhythmia). When you're anemic your heart must pump more blood to compensate for the lack of oxygen in the blood. This can lead to an enlarged heart or heart failure.

• Death. 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.