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Anemia: At a glance


What is anemia

Anemia means that you have too few red blood cells (RBCs) or hemoglobin protein (Hgb) in your blood. It can also mean that the hematocrit level is low in your blood. Remember, red blood cells are each full of hemoglobin, and hemoglobin is the protein that transports oxygen from the lungs to the cells. Hematocrit is the percentage of red blood cells in your blood versus the other components in the blood (plasma).
Below are the normal levels of red blood cells, hemoglobin, and hematocrit in men and women. Keep in mind that these normal ranges can vary based on age, altitude, and so on. Lab results lower than these values suggest that a person has anemia.
Red blood cells (RBC)4.7 to 6.1 million cells/mcL 4.2 to 5.4 million cells/mcL
Hemoglobin (Hgb)13.8 to 18.0 g/dL (8.6 to 11.2 mmol/L)12.1 to 15.1 g/dL (7.5 to 9.4 mmol/L)
Hematocrit (Hct)42 - 52%37 - 46%
Now take a moment and think about the fact that 5 million red blood cells (average between genders) get packed into a single microliter (mcL) (1/1000 of a milliliter). It's hard to think about so many red blood cells in such a small space. What if we had a speck of blood 2 microliters (mcL) in volume? How many red blood cells would be in that speck of blood?
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What's inside blood?

You can think of a red blood cell as a box holding hemoglobin molecules. Each hemoglobin molecule has two parts, called "heme" and "globin". Globin is a protein, which is like bricks and mortar for a house; it provides structure. The heme is a disk within the globin protein that holds a single atom of iron in its center. In fact, iron is what makes blood the color red when it's around oxygen, just like how iron will rust (also red!) in the presence of oxygen. Each heme can attach to 1 molecule of oxygen and each globin holds exactly 4 hemes.
This means one hemoglobin molecule holds 4 oxygen and 250 million hemoglobin molecules can be found within each red blood cell.
Hemoglobin and red blood cells
That's a lot of oxygen!  If you don’t have enough red blood cells and/or hemoglobin, then your body won’t be able to effectively transport oxygen. Check out "What is anemia?" for a quick overview.

What are the symptoms of anemia?

Anemia means that you don’t have enough red blood cells and/or hemoglobin to effectively transport oxygen around the body; all of the symptoms relate back to this problem. Oxygen doesn't get delivered effectively to the brain, muscles, and skin leading to some common symptoms like fatigue, poor concentration, weakness, and pale skin (called pallor). These symptoms are common for all anemias.
anemia - common symptoms
On the other hand, some symptoms are specific to the underlying cause of anemia:
  • Hemolytic anemias are a group of diseases in which the red blood cells are destroyed prematurely. When hemoglobin within red blood cells is broken down, the center rings of the protein (called heme) are converted into bilirubin. We usually get rid of bilirubin through urine/stool, but if there is too much of it floating around, then it can build up in the body and cause the skin to turn yellow (aka. jaundice).
  • In iron-defiency anemia, the body is not able to make hemoglobin effectively since each heme contains a bit of iron within it. Patients lacking iron sometimes get the strange urge to eat things like dirt, sand, or ice as a result. 
  • In pregnant women, the blood gets diluted as blood volume goes up but the number of red blood cells stay the same. This form of "dilutional anemia" is common, and the increased blood volume can cause heart palpitations (that feeling of your heart skipping a beat).
  • Patients with sickle cell anemia have red blood cells that are deformed and don't sail smoothly through blood vessels. When these red blood cells clog up blood vessels it can lead to intense pain in the bones or chest.
Common symptoms of anemia

What causes anemia?

There are a LOT of diseases and conditions which can lead to anemia. These diseases can be grouped together into four broad causes of having too few red blood cells (RBCs) in blood.
CausesAssociated conditions
Decreased production of RBCs  aplastic anemia , folic acid deficiency, iron deficiency anemia, kidney disease, leukemia and myelodysplastic syndrome, thalassemia, pernicious anemia (vitamin B12 deficiency), chronic diseases (e.g. HIV, Crohn's disease, etc...)
Increased destruction of RBCsglucose-6-phosphate dehydrogenase deficiency, hemolytic anemia, sickle cell anemia, transfusion reactions
Loss of RBCs (bleeding)gastrointestinal ulcers, major injuries or surgery, menstruation
Dilution of RBCs (fluid overload)pregnancy

How likely are you to get anemia?

Anemia is the most common blood disorder affecting 1.6 billion people (1 in 4), with young children and pregnant women most at risk. The likelihood you could develop anemia depends on the underlying cause of the anemia. For example:
  • Iron deficiency anemia makes up for half of all anemias globally and is more common in women due to their menstrual cycle.
  • Sickle cell anemia affects 1 in 100 people in Africa, but 1 in 3000 in the United States. This is because sickle cell anemia is a genetic disease found in people of African heritage.
Vegetarians/vegans, pregnant mothers, and alcoholics have an increased risk for nutrient deficiency anemias:
  • Vegetarians/vegans have an increased risk for iron deficiency anemia and vitamin B12 deficiency anemias because animal products contain these nutrients.
  • Pregnant women have increased iron and vitamin needs to help their fetus grow and are at an increased risk for iron, folate, and vitamin B12 deficiencies.
  • Alcohol impairs the ability of the liver to metabolize folate leading to folate deficiency anemia in alcoholics.

How can you prevent anemia?

Anemias caused by a deficiency of iron, folate, and vitamin B12 are easy to prevent with the use of vitamin supplements and a healthy diet. Other anemias such as sickle cell are genetic and cannot be prevented.
anemia - foods to eat

How do you treat anemia?

Anemia is treated by resolving the underlying cause of the anemia. Patients with anemia from sudden blood loss may be given a blood transfusion, and patients with low iron or folate levels will be given vitamin and mineral supplements. Additional medications may be given to treat the disease itself, such as steroids to depress the immune system for hemolytic anemia.

Consider the following:

  • You may have noticed that men have more red blood cells and hemoglobin in a given volume of blood than women. Why do you think that might be? Scientists are not sure yet, but one hypothesis is that higher testosterone levels in men stimulates red blood cell production.
  • Some athletes have been found "blood doping", by using products like the hormone erythropoietin before a major event.  Why would they do that? One reason is that erythropoietin (normally made in the kidney) is a hormone that helps to boost the production of RBC's. Injecting extra erythropoietin means that more RBC's are made, which means more oxygen is carried to muscles with each heart beat during the event. Blood doping is considered cheating in most sports, and it's dangerous to the athlete because rapidly getting too many RBCs increases the thickness of blood, which can lead to heart failure and stroke!

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