It is the percentage of the solid fraction of an anticoagulated blood sample.
The hematocrit blood test determines the percentage of red blood cells. The blood comprises red blood cells and white blood cells suspended in an almost transparent fluid called serum.
The hematocrit test indicates the percentage of blood per volume composed of red blood cells. The condition called “anemia” results from having too few red blood cells. Anemia causes a variety of symptoms.
Hematocrit is a basic test that can tell a doctor about a person’s health.
How is the hematocrit measured?
In most laboratories, hematocrit is measured with a machine that automatically determines a variety of blood tests known as blood counts.
The complete blood count is a numerical list of the hematocrit, as well as the concentration of hemoglobin and the three blood cell lines produced by the bone marrow (red blood cells, white blood cells, and platelets).
Another simple method is called spun hematocrit. A small amount of blood (approximately 0.05 to 0.1 ml) is placed in a thin capillary tube; the tube is sealed with wax or clay and then placed in a centrifuge.
The red blood cells accumulate in the lower part and form a red column and are separated from the pale-colored serum column by a tiny area composed of white blood cells.
The height of the whole blood in the capillary tube (red blood cells, white blood cells, and serum equal 100%).
The height of the red blood cell column divided by the size of the total fluid in the capillary tube is equal to the hematocrit (percentage of red blood cells in the total blood volume). This test lasts a few minutes.
What is a normal hematocrit?
Typical values for the hematocrit test vary according to age, sex, pregnancy, and the altitude people live and even differ slightly between various test methods.
Following are the ranges of normal hematocrit levels:
- Newborns: 55% -68%
- One (1) week of age: 47% -65%
- One (1) month of age: 37% -49%
- Three (3) months of age: 30% -36%
- One (1) year old: 29% -41%
- Ten (10) years old: 36% -40%
- Adult men: 42% -54%
- Adult women: 38% -46%
Adult pregnant women: approximately 30% – 34% lower limits and 46% upper limits.
High altitude residents : around 45% – 61% in men; 41% – 56% in women. These levels increase gradually as the altitude at which people live increases.
This is a result of the increased demand for the oxygen transport capacity of red blood cells at higher altitudes where there is a lower concentration of oxygen in the atmosphere.
These values can vary up to 7%. Consequently, a doctor should explain the importance of an individual’s hematocrit level if it is not normal.
What does a low hematocrit mean?
A low hematocrit means that the percentage of red blood cells is below the lower limits of normal for that person’s age, sex, or specific condition (for example, pregnancy or high-altitude life).
Another term for low hematocrit is anemia. Causes of low hematocrit or anemia include:
- Bleeding (ulcers, trauma, colon cancer, internal bleeding).
- Destruction of red blood cells (sickle-cell anemia, enlarged spleen).
- Reduction in the production of red blood cells (suppression of bone marrow, cancer, drugs).
- Nutritional problems (low iron, B 12, folates, and malnutrition).
- Overhydration (polydipsia, intravenous overhydration).
What does a high hematocrit mean?
A high hematocrit means that the percentage of red blood cells in a person’s blood is above normal limits for that person’s age, sex, or specific condition (for example, pregnancy or high-altitude life).
The causes of a high hematocrit include:
- Dehydration (heat exhaustion, no source of fluids available).
- Low oxygen availability (smoking, high altitude, pulmonary fibrosis).
- Genetic (congenital diseases of the heart).
- Erythrocytosis (overproduction of red blood cells by the bone marrow or polycythemia vera).
- Cor pulmonale (COPD, chronic sleep apnea, pulmonary embolism).
The treatment of high or low hematocrit depends on the underlying cause (s), the level of the hematocrit, and the general state of health of the individual.
Most people are not treated with medications or procedures if the hematocrit is slightly above or below normal levels.
Some patients with very low hematocrits may require intravenous iron, transfusions, or medications to stimulate the production of red blood cells in the bone marrow.
Some patients with very high hematocrit due to diseases like polycythemia rubra vera may require blood extraction.