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Anemia occurs when a person does not have enough healthy red blood cells. Produced in your bone marrow, red cells give blood its red color and carry oxygen to your body's tissue. Your doctor can check for anemia using two measures:

  • Hemoglobin Levels – Hemoglobin is the protein-iron combination inside each red blood cell. 
  • Hematocrit Levels – This is the number of red cells packed into a unit of blood. 

Anemia occurs when these values fall below normal, and there are not enough red cells in the body. Depending on how far you a below the normal range, anemia can be mild, moderate, or severe.


  • Mild anemia - Usually no symptoms, unless you are an athlete experiencing deteriorating performance.
  • Moderate Anemia - Some fatigue, drowsiness, or even shortness of breath on exertion.
  • Severe Anemia – High levels of fatigue.

In older patients or those with heart or vascular disease, there may be shortness of breath or angina heart pain with effort, or even stroke-like symptoms. However, if the anemia occurs very slowly, the individual often can tolerate a remarkably low red blood cell count, sometimes with very few symptoms.

Types of Anemia

Blood Loss Anemia (iron deficiency) - This most often occurs with a slow loss of blood and, with it, the body’s iron. This usually occurs in the digestive tract and may be from:

  • Ulcers in the stomach or duodenum
  • A cancer in the colon
  • Small broken blood vessels somewhere in the gut.

Females may lose a great deal of blood with excessive menstrual flow leading to iron deficiency anemia.

Malabsorption Problems - A number of conditions can occur when iron in food is not absorbed through the intestinal tract. One such condition is a hereditary disorder called celiac sprue, where the intestine is injured by the gluten protein in wheat.

Nutritional Iron Deficiency - Unhealthy or inadequate meals deficient in iron may lead to anemia in children.

Bone Marrow Failure - Bone marrow may fail to produce enough red cells for a number of reasons. One is aplastic anemia, the cause of which is usually not known. Certain drugs may also cause this problem.

Chronic Illness and Malignancies - Many types of malignancies, leukemia, and chronic disorders such as tuberculosis or a combination of several chronic illnesses (lung, kidney, liver) may lead to anemia.

Chronic Kidney Disease – Erythropoietin, a hormone made by the kidney, tells the bone marrow to make more red blood cells when there are not enough. People with chronic kidney disease, especially those needing dialysis, lack this hormone and become anemic.

Large Red Blood Cell Anemia (macrocytic anemia) – This is condition in which your body has overly large red blood cells and not enough normal red blood cells. Examples include:

  • Vitamin B12 deficiency or pernicious anemia.
  • A lack of folic acid in the diet. This is rare since folic acid is an FDA required additive to many foods.
  • Liver diseases, such as cirrhosis

Red Cell Destruction (hemolytic anemia) - Certain immune disorders as well as some drugs and diseases may attack red blood cells, destroying them and leading to anemia.


As noted, anemia is present when the red cell count is low. Simply measuring the size of the red blood cell and how much hemoglobin is in the cell will give a clue as to the cause. Your physician will usually need to do certain testing to determine the cause and prescribe the necessary treatment.

  • Blood studies. Measuring iron, vitamin B12, folic acid and certain other substances will often provide useful information.
  • Endoscopy. Visual exams of the intestinal tract under sedation using a flexible viewing endoscope can help detect stomach ulcers and colon cancers, both common causes of anemia.
  • Imaging. These tests may include X-rays of the stomach and intestinal tract, and possibly ultrasound and CAT (CT) exams.
  • Others. There are times when all these test do not provide an answer and additional tests such as a bone marrow biopsy may be recommended.


With so many causes for anemia, no single therapy is right for all.

  • If there is bleeding from a stomach ulcer, the ulcer must be healed.
  • If there is blood loss from colon cancer, your provider will likely surgically remove the cancer.
  • If there is excessive menstrual flow, medications or surgery may be needed

In all of these cases of blood loss anemia, taking oral iron is appropriate while treating the underlying problem. Your provider can easily correct Vitamin B12 or folic acid deficiency once diagnosed.

Chronic kidney disease or a failure of the bone marrow to make red cells may not be as easily treated. If the anemia is severe or causing disabling symptoms, then blood transfusions may be necessary. However, taking oral iron or receiving a transfusion by themselves are never enough. The goal is always to treat the underlying cause.

This content was last medically reviewed in May 2022 by Sharlotte Manley, MSN, FNP, Erlanger Gastroenterology.