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Anemia happens when there is a decreased number of circulating red blood cells in the body. It is the most common blood disorder in the general population. Symptoms can include headaches, chest pains, and pale skin.

It currently affects more than 3 million Americans and an estimated 1.62 billion people, globally.

It often results when other diseases interfere with the body's ability to produce healthy red blood cells or abnormally increase red blood cell breakdown or loss.

Fast facts on anemia

Here are some key points about anemia. More detail is in the main article.

  • Anemia affects an estimated 24.8 percent of the world's population.
  • Pre-school children have the highest risk, with an estimated 47 percent developing anemia, globally.
  • More than 400 types of Anemia have been identified.
  • Anemia is not restricted to humans and can affect cats and dogs.

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There are many potential causes of anemia.

The most common symptom of all types of anemia is a feeling of fatigue and a lack of energy.

Other common symptoms may include:

  • paleness of skin
  • fast or irregular heartbeat
  • shortness of breath
  • chest pain
  • headache
  • light-headedness

In mild cases, there may be few or no symptoms.

Some forms of anemia can have specific symptoms:

  • Aplastic anemia: fever, frequent infections, and skin rashes
  • Folic acid deficiency anemia: irritability, diarrhea, and a smooth tongue
  • Hemolytic anemia: jaundice, dark colored urine, fever, and abdominal pains
  • Sickle cell anemia: painful swelling of the feet and hands, fatigue, and jaundice

The body needs red blood cells to survive. They carry hemoglobin, a complex protein that contains iron molecules. These molecules carry oxygen from the lungs to the rest of the body.

Some diseases and conditions can result in a low level of red blood cells.

There are many types of anemia, and there is no single cause. It can sometimes be difficult to pinpoint the exact cause.

Below is a general overview of the common causes of the three main groups of anemia:

1) Anemia caused by blood loss

The most common type of anemia—iron deficiency anemia—often falls into this category. It is caused by a shortage of iron, most often through blood loss.

When the body loses blood, it reacts by pulling in water from tissues outside the bloodstream in an attempt to keep the blood vessels filled. This additional water dilutes the blood. As a result, the red blood cells are diluted.

Blood loss can be acute and rapid or chronic.

Rapid blood loss can include surgery, childbirth, trauma, or a ruptured blood vessel.

Chronic blood loss is more common in cases of anemia. It can result from a stomach ulcer, cancer, or tumor.

Causes of anemia due to blood loss include:

2) Anemia caused by decreased or faulty red blood cell production

Bone marrow is a soft, spongy tissue found in the center of bones. It is essential for the creation of red blood cells. Bone marrow produces stem cells, which develop into red blood cells, white blood cells, and platelets.

A number of diseases can affect bone marrow, including leukemia, where too many abnormal white blood cells are produced. This disrupts normal production of red blood cells.

Other anemias caused by decreased or faulty red blood cells include:

  • Sickle cell anemia: Red blood cells are misshapen and break down abnormally quickly. The crescent-shaped blood cells can also get stuck in smaller blood vessels, causing pain.
  • Iron-deficiency anemia: Too few red blood cells are produced because not enough iron is present in the body. This can be because of a poor diet, menstruation, frequent blood donation, endurance training, certain digestive conditions, such as Crohn's disease, surgical removal of part of the gut, and some foods.
  • Bone marrow and stem cell problems: Aplastic anemia, for example, occurs when few or no stem cells are present. Thalassemia occurs when red blood cells cannot grow and mature properly.
  • Vitamin deficiency anemia: Vitamin B-12 and folate are both essential for the production of red blood cells. If either is deficient, red blood cell production will be too low. Examples include megaloblastic anemia and pernicious anemia.

3) Anemia caused by the destruction of red blood cells

Red blood cells typically have a life span of 120 days in the bloodstream, but they can be destroyed or removed beforehand.

One type of anemia that falls into this category is autoimmune hemolytic anemia, where the body's immune system mistakenly identifies its own red blood cells as a foreign substance and attacks them.

Excessive hemolysis (red blood cell breakdown) can occur for many reasons, including:

  • infections
  • certain drugs, for example, some antibiotics
  • snake or spider venom
  • toxins produced through advanced kidney or liver disease
  • an autoimmune attack, for instance, because of hemolytic disease
  • severe hypertension
  • vascular grafts and prosthetic heart valves
  • clotting disorders
  • enlargement of the spleen

There is a range of treatments for anemia. They all aim to increase the red blood cell count. This, in turn, increases the amount of oxygen the blood carries.

Treatment will depend on the type and cause of anemia.

  • Iron deficiency anemia: Iron supplements (which are availble to buy online) or dietary changes. If the condition is due to loss of blood, the bleeding must be found and stopped.
  • Vitamin deficiency anemias: Treatments include dietary supplements and B-12 shots.
  • Thalassemia: Treatment includes folic acid supplementation, removal of the spleen, and, sometimes, blood transfusions and bone marrow transplants.
  • Anemia of chronic disease: This is anemia associated with a serious, chronic underlying condition. There are no specific treatments, and the focus is on the underlying condition.
  • Aplastic anemia: The patient will receive blood transfusions or bone marrow transplants.
  • Sickle cell anemia: Treatment includes oxygen therapy, pain relief, and intravenous fluids. There may also be antibiotics, folic acid supplements, and blood transfusions. A cancer drug known as Droxia or Hydrea is also used.
  • Hemolytic anemias: Patients should avoid medication that may make it worse and they may receive immunosuppressant drugs and treatment for infections. Plasmapheresis, or blood-filtering, might be necessary in some cases.

There are more than 400 types of Anemia currently known, and these are divided into three main groups according to their cause:

  • Anemia caused by blood loss
  • Anemia caused by decreased production or production of faulty red blood cells
  • Anemia caused by the destruction of red blood cells

Types of anemia within these categories include:

If the anemia is caused by nutritional deficiencies, a change to an iron-rich diet can help alleviate the symptoms. The following foods are high in iron:

  • iron-fortified cereals and breads
  • dark-green leafy vegetables, for instance, curly kale and watercress
  • pulses and beans
  • brown rice
  • white and red meats
  • nuts and seeds
  • fish
  • tofu
  • eggs
  • dried fruits, including apricots, raisins, and prunes

Anemia can occur in people of all ages and race, both males and females. However, certain factors increase the risk.

These include:

  • menstruation
  • pregnancy and childbirth
  • being born preterm
  • being aged 1 to 2 years
  • having a diet that is low in vitamins, mineral, and iron
  • losing blood from surgery or injury
  • long-term or serious illness, such as AIDs, diabetes, kidney disease, cancer, rheumatoid arthritis, heart failure, and liver disease
  • family history of inherited anemias, such as sickle cell anemia
  • intestinal disorders-affects absorption of nutrients

The outlook for a person with anemia depends on the cause. Many cases of anemia can be prevented or solved through a change in diet.

Some types can last for a long time, and some can be life-threatening without treatment.

Anyone who feels persistently weak and tired should see a doctor to check for anemia.

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A complete blood count can help diagnose anemia.

There are different ways to diagnose anemia, but the most common is a blood test known as a complete blood count (CBC).

This measures a number of blood components, including hemoglobin and hematocrit levels, or the ratio of the volume of red blood cells to the total volume of blood.

A CBC can give an indication of the person's overall health and whether they have any conditions, such as leukemia or kidney disease.

If the red blood cell, hemoglobin, and hematocrit levels are all below "normal," then anemia is likely.

However, it does not provide a definitive diagnosis. It is possible to be outside the normal range but still healthy.