Haematocrit (HCT)

An HCT blood test or Hematocrit is an investigation of the blood that measures the amount of red blood cells (RBCs). In addition to the red blood cells, blood is made up of plasma, platelets and white blood cells. Thus, to measure the amount of these RBCs, hematocrit investigation is used.

What Is HCT In Blood Test?

HCT stands for Hematocrit in a blood test. Hematocrit is a measure of the volume of red blood cells (RBCs) in the blood. It represents the percentage of the total blood volume that is occupied by red blood cells.

HCT Blood Test Uses

HCT Blood Test is part of a simple blood test that measures a percentage of red blood cells. These cells are made up of iron called haem, and a protein called globin, and this combination is called hemoglobin. The purpose of hemoglobin in the RBCs is to bind to the oxygen from the lungs and disperse is to the tissues of the rest of the body. Abnormal levels of hematocrit can indicate presence of blood disorders and indicate an underlying medical condition.

Why Is An HCT Blood Test Done?

Hematocrit is done as part of regular physical examination or to monitor a health condition such as anemia or polycythemia.

If the levels of red blood cells, is lower than normal, the condition is called anemia and presents with:

• Dizziness
• Headache
• Shortness of breath
• Fatigue
• Arrhythmia
• Weakness

On the other hand, too many red blood cells constitute a condition called polycythemia. It presents with:

• Itchy skin particularly after showering and bathing
• Red face
• Headache
• Shortness of breath
• Bleeding from gums
• Blind spots, blurry or double vision

HCT Blood Test Procedure

• A vein is sought to draw the blood from. The most common site for drawing blood is from the inside of the elbow.
• A tourniquet is then placed on the upper arm to make the veins prominent.
• The site is then cleaned and needle is inserted to draw the blood.
• The needle is thereafter removed and the area bandaged.

HCT Normal Range

Normal levels of hematocrit can differ based on the gender, age and the altitude of residence. For people residing in the mountains or areas of high altitude, the hematocrit can be higher. This is because these areas have lesser oxygen to bind with the RBCs. In return, the body responds by making more RBCs to carry more oxygen.

Another factor that can affect the hematocrit level is pregnancy. In pregnant women, the fluid levels of the blood are higher than normal, thereby giving a low reading of the hematocrit.

Typically, the normal range of hematocrit is:

• Adult men: 41 to 50 percent
• Adult women: 36 to 44 percent
• Newborns: 45 to 61 percent
• Infants 32 to 42 percent

When Is Hematocrit Deranged?

Deranged hematocrit is indicative of a number of conditions, include:

• High levels of hematocrit are seen in:

• Heart conditions: cardiovascular diseases result in high hematocrit levels.
• Dehydration: when the water content in body decreases, it causes increase in the ratio of red blood cells and therefore raised hematocrit.
• Lung disease: scarring of the lungs and other lung diseases raise hematocrit as well.
• Smoking: cigarette smoke indirectly raises hematocrit through stimulation of erythropoietin and production of red blood cells.
• Testosterone use: hematocrit levels rise due to use of testosterone.
• Carbon monoxide poisoning: another cause of raised hematocrit is carbon monoxide poisoning which decreases the level of plasma in the blood and raises the percentage of red blood cells.

• Low levels of hematocrit are seen in:

• Blood loss: bleeding and loss of blood result in fewer red blood cells and thus lower hematocrit.
• Kidney disease: this indirectly affects hematocrit through decreased production of erythropoietin.
• Leukemia: can displace the normal cells of the bone marrow which can reduce the production of red blood cells.
• Thyroid disease: hypothyroidism can indirectly impact red blood cell production and result in lower hematocrit.
• Hyponatremia: too much water in the plasma as seen in dilutional hyponatremia waters down the blood and results in low hematocrit.
• Hemolytic anemia: in this type of anemia, there is breakdown of red blood cells, which eventually lowers their percentage in the blood and therefore lowers the hematocrit level.