Anemia is simply defined as a low red blood cell count.  Red cells are produced inside the bone marrow.  The red cell is what makes the blood red.  Its only purpose is to carry oxygen to the body’s tissues which need it for healthy function.  Inside each red cell is a protein and iron combination that is called hemoglobin.  This can be measured.  A low hemoglobin level in the blood means anemia.  A second way to measure anemia is called the hematocrit.
Hemoglobin  12 to 16 gm% - females
                     14 to 18 gm% - males
Hematocrit  36 to 48 volumes% - females
                   42 to 53 volumes% - males
When these values fall below normal, it is called anemia.  There are not enough red cells in the body.  If you are a little bit below the normal range, it is called a mild anemia.  A bit more and it is moderate anemia.  And with values very below normal, it is severe anemia.
There are usually no symptoms with a mild anemia, unless the person is an athlete who finds his or her performance deteriorating.  A moderate anemia may cause some fatigue, drowsiness or even shortness of breath on exertion.  A severe anemia can cause severe fatigue.  In older patients or those with heart or vascular disease, there may be shortness of breath or chest pain with exertion, 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
There are many causes of anemia, so many it is not possible to cover them all.  However, there are certain major categories which are useful to know.
• 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, or less commonly, from 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.  There are a number of conditions where iron in food is not absorbed through the intestinal tract.  These are called malabsorption problems which means the iron is not absorbed from the intestine.  One such condition is a hereditary disorder called celiac sprue, where the intestine is injured by the gluten protein in wheat.  In children from poor families, the diet may be deficient in iron and cause anemia.  This is called nutritional iron deficiency.
• Large red blood cell anemia (macrocytic anemia) - There are a number of causes where there is anemia, but the remaining red cells are increased in size.  This is called a macrocytic or large red cell anemia.  A deficiency of vitamin B 12, or pernicious anemia, is one example.  A lack of folic acid in the diet and severe liver disease, such as cirrhosis, are other causes of this type of anemia.  Folic acid deficiency is rare since folic acid is now added to so many foods by FDA requirements.
• Bone marrow failure - There are a number of reasons why the bone marrow may fail to produce enough red cells.  One is aplastic anemia, the cause of which is usually not known.  Certain drugs may also cause this problem.
• Red cell destruction (hemolytic anemia) - Certain immune disorders as well as some drugs and diseases may attack the red cells in the blood, destroying them and leading to anemia.
• Chronic kidney disease - There is an important hormone called erythropoietin that is made by the kidney.  It tells the bone marrow to make more red cells when there are not enough.  People with chronic kidney disease, especially when they require kidney dialysis, lack this hormone and therefore become anemic.
• Chronic illnesses and malignancies - Many types of malignancies, leukemias and chronic disorders such as tuberculosis or a combination of several chronic illnesses (lung, kidney, liver) may lead to an 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.  The physician will usually need to do certain testing to arrive at a specific cause and so determine the necessary treatment.
• Blood studies - Measuring iron, vitamin B12, folic acid and certain other substances will often provide useful information.
• Imaging - X-rays of the stomach and intestinal tract may be done.  An ultrasound and CAT (CT) exam may also be necessary.
• Endoscopy - These are visual exams of the intestinal tract under sedation using a flexible viewing endoscope.  Ulcers of the stomach and cancers of the colon, both common causes of anemia, can be diagnosed this way.
• Others - There are times when all these tests do not provide an answer and additional tests such as a bone marrow biopsy may be recommended.
Since there are so many causes for anemia, no single therapy is right for all.  If there is bleeding from a stomach ulcer, then the ulcer must be healed.  If there is blood loss from colon cancer, then, of course, the cancer needs to be surgically removed.  Likewise, if there is excessive menstrual flow, this must be corrected by medications or surgery.  Vitamin B 12 or folic acid deficiency are easily corrected 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 underlying cause must always be sought.
The meaning of anemia is very simple, not enough red blood cells in the body to carry oxygen to the tissues.  The cause is usually found and corrected, However, there are instances when making the diagnosis may be difficult.  By working with the physician, a satisfactory outcome usually occurs.
Note: the information in this section is provided as a supplement to information discussed with your healthcare provider.  It is not intended to serve as a complete description of a particular topic or substitute for a clinic visit.