The hematocrit corresponds to volume occupied by red blood cells (red blood cells or erythrocytes) in the blood relative to the total volume of blood. Expressed as a percentage, the hematocrit level is measured during a blood test to prevent, diagnose or monitor certain blood abnormalities such as anemia or polycythemia.

An important value during a blood test

The hematocrit level is one of the values ​​commonly measured during a blood count, also called a blood test or blood count (CBC). Commonly performed, the blood count consists of a quantitative and qualitative analysis of the elements present in the blood, including:

• red blood cells, also called erythrocytes or more commonly red blood cells;
• leukocytes, better known as white blood cells;
• thrombocytes, which correspond to blood platelets.

A test for red blood cells

The hematocrit corresponds to volume occupied by red blood cells in the blood relative to the total volume of blood. The hematocrit level is expressed as a percentage.

A complementary and essential blood test

The hematocrit level is measured in addition to other blood tests including the measurement of red blood cells. By measuring the volume occupied by red blood cells in the volume of whole blood, the hematocrit makes it possible to obtain two other essential blood values:

• le mean corpuscular volume (VGM), which assesses the size of red blood cells circulating in the blood;
• mean corpuscular hemoglobin concentration (CCMH), which assesses the mass concentration of red blood cells.

An analysis for the diagnosis or monitoring of certain diseases

In addition to other blood tests, the hematocrit level makes it possible to diagnose certain diseases, or to follow their evolution. In particular, it allows the diagnosis and monitoring of:

• theanemia, a blood abnormality characterized by an abnormal drop in red blood cells;
• polycythemia, a blood abnormality characterized by an abnormally high level of red blood cells;
• the dehydration.

A preventive control blood count

Like other measurements of a blood count, the hematocrit level can be measured for check for blood abnormalities. These blood tests are essential for early diagnosis of certain abnormalities and limit the risk of complications.

If anemia is suspected

In addition to measuring the red blood cell level, the hematocrit level can be measured for confirm the diagnosis of anemia. These measures are usually ordered by a doctor when the patient presents:

• general fatigue and lack of energy;
• muscle weakness;
• dizziness and faintness;
• shortness of breath;
• a pallor.

If polycythemia is suspected

Similar to anemia, a doctor may order a measurement of the red blood cell level and the hematocrit level for confirm the diagnosis of polycythemia. This usually manifests itself by:

• dizziness ;
• headaches ;
• visual disturbances;
• tinnitus;
• skin redness;
• tingling in the fingers;
• itching on contact with water.

In case of dehydration

The hematocrit level and the red blood cell level can also be measured for assess the severity of dehydration. These measurements are usually performed when the patient presents:

• intense thirst;
• dryness of the mouth and lips;
• a lack of sweat and / or urine;
• loss of muscle strength or abnormal fatigue.

Analysis of a blood count: how to find the hematocrit level?

The analysis of a complete blood count takes into account various measurements including the hematocrit level. On the blood count results sheet, the hematocrit level can be identified by the abbreviations “Hct” or “Ht”.

Hematocrit level: what are the normal values?

In a blood count, the reference values ​​for the hematocrit level are:

• between 40% and 52% in humans;
• between 35% and 47% in women;
• between 32% and 45% in children.

Low hematocrit: what interpretation?

A hematocrit level below the reference values ​​is often a sign of anemia. Characterized by an abnormally low level of red blood cells in the blood, this can have many explanations:

• theiron deficiency anemia, which is caused by iron deficiency;
• thevitamin B12 deficiency anemia ;
• hemorrhagic anemia, which is caused by heavy blood loss;
• hemolytic anemia, which is caused by too rapid destruction of red blood cells;
• theaplastic anemia, which is due to insufficient synthesis of red blood cells.

A low hematocrit can nevertheless have other origins such as sickle cell anemia, a genetic disease characterized by an alteration of red blood cells.

In the event of a low hematocrit, the diagnosis requires the analysis of other parameters including the level of red blood cells.

Low hematocrit in pregnant women: what to do?

During pregnancy, many blood parameters change. This is the case with the hematocrit level which tends to drop. This decrease is explained by an increase in blood volume in pregnant women. This change is normal and essential for the development of the future baby.

A low hematocrit level in pregnant women nevertheless requires medical advice because it can also be a sign of anemia. Due to an increased need for iron, iron deficiency anemia is particularly common during pregnancy.

High hematocrit: what interpretation?

A hematocrit level above the reference values ​​may be a sign of polycythemia. Characterized by an abnormally high level of red blood cells, this can have several explanations such as:

• la Vasquez disease ;
• certain lung diseases;
• congenital heart disease.

A high hematocrit can also be seen during a severe dehydration of the body. Other external factors can also cause an increase in the hematocrit, including:

• smoking;
• and stays at high altitude.

In the event of a high hematocrit, the diagnosis requires the analysis of other parameters including the level of red blood cells.

The hematocrit level is measured during a blood count. This consists of a blood test. This is usually done in a vein in the arm. In children and newborns, this blood sample is rather taken from the fingertip or from the heel.