Anemia is having a low number of red blood cells. It is the most common blood condition, affecting about 6% of the population in the US and almost 10% of the population worldwide. Women and young children are more likely to suffer from anemia, as are people with long-term illnesses. The name comes from the Ancient Greek: ‘an’ (lack of) ‘haima’ (blood).
The red blood cells are filled with a red iron-containing protein called hemoglobin, which gives blood its dark red color. Hemoglobin captures oxygen in the lungs and delivers it throughout the body. It also carries carbon dioxide out of the body to the lungs. Having anemia, with too few red blood cells, means that there is not enough hemoglobin, so the tissues and organs do not get adequate oxygen. Hence, the symptoms of anemia (see below) include fatigue and shortness of breath because the tissues and organs are not receiving enough oxygen to work properly.
There are many types of anemia, each having different causes and treatments. Some types are mild, for example, arising during pregnancy, while more severe types are usually associated with serious medical conditions. Anemia may be genetic, and can be passed to infants. Women are more likely to suffer iron-deficiency anemia than men because of menstrual blood loss or high oxygen demands in pregnancy. Older patients with kidney disease or other chronic conditions are also at higher risk.
The major causes of anemia are not enough red cells produced in the body, red cells being lost faster than they can be replaced and destruction of red blood cells. Anemia is diagnosed when a blood sample has ‘low hemoglobin’ or ‘low hematocrit’ (meaning a low red blood cell number in the blood).
The type of anemia determines the appropriate treatment. This may be simply taking iron and other supplements and eating a healthy diet through to having a medical intervention.
Anemia Types and Causes
There are very many types of anemia. They can be divided into four main groups:
Anemia Caused by Blood Loss
Blood can be lost by bleeding. If this happens slowly, the effects may not be evident for a long while. This type of anemia is caused by:
- Gastrointestinal conditions such as ulcers, hemorrhoids, gastritis, and cancer. Parasitic infections such as hookworm can also cause internal bleeding
- Non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen, which can cause ulcers and gastritis
- Heavy menstruation (or heavy period), possibly associated with fibroids
- Trauma or surgery
Anemia Caused by Decreased or Faulty Red Blood Cell Production
The blood cells are produced in the bone marrow. If the bone marrow is compromised it may not create enough new red blood cells. Alternatively, the red blood cells that are produced fail to work properly because of a genetic defect or a lack of certain minerals and vitamins during their development that allow the red blood cells to form and function normally. The conditions causing this kind of anemia include:
- Aplastic anemia: There are too few or no bone marrow stem cells as a result of a genetic fault, because of bone marrow injury caused by medications, radiation, chemotherapy, or infection, or because of cancers such as multiple myeloma or leukemia.
- Lead poisoning: Lead is toxic to bone marrow, leading to reduced red blood cell production.
- Thalassemia: This is a problem with hemoglobin formation. Thalassemia is genetic, usually affecting people of Mediterranean, African, Middle Eastern, and Southeast Asian descent. Thalassemia can be mild or life-threatening, the most severe form being Cooley’s anemia.
Vitamins B12 and B9 (folate) Deficiency
Vitamins B12 and folate are required to make red blood cells.
- Dietary deficiency: eating only little or no meat might not provide enough vitamin B12. Eating too few vegetables or overcooking them might not provide sufficient folate.
- Megaloblastic anemia: the bone marrow releases large immature red blood cells when there is not enough vitamin B12 and folate during their production
- Pernicious anemia: insufficient vitamin B12 is absorbed from food
- Other causes of vitamin deficiency: medications, alcohol abuse and intestinal diseases such as tropical sprue.
- Iron is needed to make hemoglobin, the oxygen carrying molecule. Iron-deficiency anemiais a consequence of not having enough iron in the body.
- The diet may lack iron, especially in infants, children, teens, vegans, and vegetarians
- Consumption of certain drugs, foods, and caffeinated drinks can reduce iron absorption
- Digestive conditions such as Crohn’s disease or the removal of part of the stomach or small intestine can reduce iron uptake
- Other causes of iron deficiency are endurance training, pregnancy and breastfeeding, menstruation, or a chronic slow bleed, usually in the intestine.
Sickle Cell Anemia
Sickle cell anemia is a genetic disorder which, in the USA, affects mainly African Americans and Hispanic Americans. Red blood cells are usually round, but a genetic fault causes then to become crescent-shaped. These misshapen red blood cells are broken down quickly, reducing the oxygen supply to the organs and tissues. The crescent-shaped red blood cells also get stuck in narrow blood vessels and cause pain.
Inflammation releases small hormone-like molecules that suppress the bone marrow, and interfere with the production of red blood cells. Inflammatory diseases include cancer, HIV/AIDS, rheumatoid arthritis, kidney disease, Crohn’s disease and others.
Other conditions affecting the bone marrow
Several diseases, such as leukemia and myelofibrosis, 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.
Anemia Caused by Destruction of Red Blood Cells
Hemolytic anemias are a group of anemias in which red blood cells are destroyed faster than bone marrow can replace them. Certain blood diseases increase red blood cell destruction. The causes of hemolytic anemia are not always clear, but may include:
- Fragile red blood cells may burst during circulation causing hemolytic anemia. Babies may be born with this condition, or it can develop later.
- An attack by the immune system by autoimmunity (such as lupus). When this occurs in a baby before or after birth, this is called ‘hemolytic disease of the newborn’.
- Genetic conditions such as sickle cell anemia, thalassemia, and thrombotic thrombocytopenic purpura (TTP)
- Enlarged spleen. This can, in rare cases, trap red blood cells and destroy them too early.
- Infections, drugs, snake or spider venom, or certain foods
- Toxins from advanced liver or kidney disease
- Vascular grafts, prosthetic heart valves, tumors, severe burns, chemicals, severe hypertension, and clotting disorders
Anemia associated with other chronic conditions
Anemia may arise when there are not enough hormones to make red blood cells. Conditions that cause this type of anemia include:
Anemia signs and symptoms vary depending on the cause. Mild symptoms of anemia may be unnoticeable. If anemia is caused by a chronic disease, the disease may can mask symptoms. With more severe anemia, as the number of red blood cells decreases, the following symptoms may be observed:
If untreated, anemia can cause severe fatigue, complications in pregnancy, heart problems and death.
Anemia Risk factors
Certain factors increase the risk of anemia:
An intestinal disorder, such as Crohn’s disease or celiac disease, that affects the absorption of nutrients in the small intestine
A lack of iron, vitamin B-12 and folate in the diet
Lacking nutrients during pregnancy
Pregnancy in women not taking a multivitamin with folic acid and iron
Heavy menstruation in premenopausal women
Bleeding internally with stomach and gastrointestinal lesions
Chronic conditions such as cancer, kidney failure or diabetes
Family history of sickle cell anemia
Genetic inheritance in families with a history of sickle cell anemia
Some mild types of anemia can be prevented. Iron and vitamin deficiency anemias can be avoided by eating a diet that has a variety of vitamins and minerals. Iron-rich foods include beef and other meats, beans, lentils, iron-fortified cereals, dark green leafy vegetables, and dried fruit. Folate is found in fruits and fruit juices, dark green leafy vegetables, green peas, kidney beans, peanuts, and enriched grain products, such as bread, cereal, pasta and rice. Foods rich in vitamin B12 include meat, dairy products, fortified cereal and soy products. Vitamin C, which helps to increase iron absorption, is present in citrus fruits and juices, peppers, broccoli, tomatoes, melons and strawberries.
A diagnosis of anemia is made using a blood test called the complete blood count. This test measures the number of red blood cells, the amount of hemoglobin they carry, their size and their appearance under a microscope. Once a diagnosis of anemia is made, various tests are done to determine the underlying cause of the disease. Family and medical histories are important pointers to the cause.
Treatment depends on the type of anemia. There are lot of causes, so there are also many treatments available.
- Aplastic anemia might need medication, blood transfusions or a bone marrow transplant
- Hemolytic anemia might require medication to suppress the immune system.
- Internal blood loss might necessitate surgery to find and stop the bleeding.
- Deficiencies of iron, vitamin B12 and folate can be treated with supplements and a change in diet. Depending on the type of anemia, iron may be taken by mouth or by injection.
- Sickle cell anemia treatment includes folic acid supplements, antibiotics as required or oxygen therapy. A drug, called hydroxyurea may be prescribed to decrease sickle cell pain crises. A medication called voxelator can help red blood cells keep their proper shape, while crizanlizumab-tmca reduces the blood cells from sticking together and blocking vessels. L-glutamine oral powder helps to control pain and guard against a condition called acute chest syndrome.
- Thalassemia is usually untreated but, in severe cases, blood transfusions, a bone marrow transplant, or surgery may be necessary.
- Increasing the output of red blood cells from the bone marrow is a possibility in severe anemia, using hormone-like agents called ‘erythropoiesis-stimulating medications’.
- Transfusion dependent anemia is a form of anemia where ongoing blood transfusion are required. Conditions such as myelodysplastic or thalassemia may result in transfusion dependence. However, repeated blood transfusions may cause iron overload which may require treatment with ‘chelation therapy’ to bind and remove the excess iron.
- Splenectomy is the removal of an organ called the spleen. The spleen balances out the bone marrow production of new red blood cells by capturing and destroying, particularly, the older red cells. Removal of the spleen, especially when it is enlarged, may increase the number of red blood cells in the circulation.
- Hyperbaric oxygen is given in severe, usually acute, anemia when oxygen delivery to the tissues and organs is insufficient, in patients who cannot be given blood transfusions for blood transfusion for medical or religious reasons.