Red Blood Cell Count – Low & High

Erythrocyte (RBC) Count High & Low Polycythemia & Anemia Symptoms, Causes & Effects Presentation for Biology / Medical Students



High RBC Count - Increase in the red blood cell count is known as polycythemia. If it occurs in physiological conditions, it is called physiological polycythemia. It occurs in the following conditions:

1. Age

At birth, the red blood cell count is 8 -10 millions/cu mm of blood. The count decreases within 10 days after birth due to destruction of cells causing physiological jaundice in some infants. However, in infants and growing children, the cell count is at a level higher than the value in adults.

2. Sex

Before puberty and after menopause in females the red blood cell count is similar to that in males. During repro­ductive period of females, the count is less than in males (4.5 millions/cu mm).

3. High Altitude

The inhabitants of mountains (above 10,000 feet from mean sea level) have an increased red blood cell count of more than 7 millions/cu mm. This is due to hypoxia in high altitude. During hypoxia, the erythropoietin is released from the kidneys. The erythropoietin in turn stimulates the bone marrow to produce more red blood cells.

4. Muscular Exercise

There is a temporary increase in red blood cell count after exercise. This is because of mild hypoxia and contraction of spleen , which is the reservoir of blood.

5. Emotional Conditions

The red blood cell count is increased during the emotional conditions like anxiety, because of sympathetic stimula­tion.

6. Increased Environmental Temperature

The increase in the atmospheric temperature increases red blood cell count.

7. After Meals

There is a slight increase in the red blood cell count after taking meals.

Low RBC Count - Decrease in red blood cell count occurs in the following physiological conditions:

1. High Barometric Pressures

At high barometric pressures as in deep sea, when the oxygen tension of blood is higher, the red blood cell count decreases.

2. After Sleep

The red blood cell count decreases slightly after sleep.

3. Pregnancy

In pregnancy, the red blood cell count decreases. This is because of increase in extracellular fluid volume. Increase in extracellular fluid volume, increases the plasma volume also resulting in hemodilution. So, there is a relative reduction in the red blood cell count.


Pathological Polycythemia

The abnormal increase in the red blood cell count is called polycythemia. The red cell count increases above 7 millions/cu mm of the blood. Polycythemia is of two types, the primary polycythemia and secondary polycythemia.

Primary Polycythemia — Polycythemia Vera

Primary polycythemia is otherwise known as polycythemia, vera. It is a disease with persistent increase in red blood cell count above 7 millions/cu mm of blood. This is always associated with increased white blood cell count above 24,000/cu mm of blood. Polycythemia vera occurs in myeloproliferative disorders like malignancy of red bone row.

Secondary Polycythemia

This is secondary to some of the pathological conditions (diseases) such as:

1. Respiratory disorders like emphysema.

2. Congenital heart disease.

3. Ayerza's disease—condition associated with hyper­trophy of right ventricle and obstruction of blood flow to lungs.

4. Chronic carbon monoxide poisoning.

5. Poisoning by chemicals like phosphorus and arsenic.

6. Repeated mild hemorrhages.


The abnormal decrease in red blood cell count is called anemia.