What is HCT? What is low HCT?

By | 5 May 2021

What is HCT? What is low HCT?

Red blood cells, called red blood cells, are responsible for the transmission of oxygen passing through the lungs to other tissues and organs in the body. Apart from oxygen, it also takes part in the transport of carbon dioxide molecules. Erythrocytes take the carbon dioxide formed as a result of the cells’ use of oxygen as a result of their metabolism, and carry them to the lungs and allow them to be excreted.

Red blood cells (erythrocytes) are produced in the bone marrow. They are formed by the division of stem cells in the bone marrow. Certain substances and hormones are necessary for the production of erythrocytes. Examples include erythropoietin, vitamin B12, folic acid, and iron mineral.

While there are approximately 4.8 million red blood cells in a cubic millimeter of blood in women, this figure is 5.4 million for men. The transport of oxygen and carbon dioxide is due to the hemoglobin contained in red blood cells. Since hemoglobin is a molecule containing iron, it causes the blood to appear red. Disc-shaped red blood cells do not have a nucleus. Care should be taken as changes in the number of these cells can occur as a symptom of various diseases.

What is the hematocrit?

Hematocrit refers to the ratio of the volume of red blood cells to the amount of circulating blood. Mathematically, it is calculated by multiplying the average red blood cell volume (MCV) measured with the aid of the devices and the number of erythrocytes. Normal hematocrit values ​​are accepted between 35-45%. Depending on gender and age, there may be differences in the accepted range of values. The range of values ​​considered normal for hematocrit, especially in children younger than 15 years, was determined separately for each age.

What is HCT in blood?

Hematocrit value is one of the parameters included in the complete blood count test. The most common reason for examination is anemia. The answer to the question of what is meant by HCT can be given as “the brief expression of hematocrit in the report containing test results”.

Why Measure Hematocrit and What is the Assumed Normal HCT Value?

Hematocrit measurement is part of the complete blood count test. Detecting the part of the red blood cells in the bloodstream can be useful both in detecting various diseases and in examining the course of treatment for some diseases. Hematocrit refers to the volume of red blood cells in the blood. While the value accepted as normal in women varies between 35-45%, this figure is between 39-50% in men. The answer to questions such as what is the Hct height and what is the low Hct is to determine this parameter below or above normal limits.

This value, measured by hematological analysis methods, shows the feature of not being the same everywhere in the vein. Red blood cells are externally prone to post-traumatic deformity and therefore move in the middle part of the vessel. In the area close to the vessel wall, a blood fluid called plasma-free plasma circulates. For this reason, the HCT ratio is approximately 80% in the middle part of the blood, while it is almost zero in areas close to the wall.

Red blood cells from the oxygenated part of the blood and there is a parallel between their number and the HCT value. Although the oxygen-carrying capacity in the blood seems to increase with the increase of HCT, this may cause results such as the blood being less fluid and its density increases. Increasing HCT so that the fluidity of the blood does not deteriorate may contribute to increasing the amount of oxygen transferred to tissues.

The hematocrit test can be of diagnostic value for a variety of health problems:

  • Anemia
  • Leukemia
  • Dehydration (loss of fluid)
  • Lack of various nutrients

How Is Hematocrit (HCT) Measured?

To measure hematocrit, the blood sample must be taken from the person first. This process can be performed by taking samples from the person’s fingertip or the veins in his arm. If the hematocrit value is a part of the complete blood count, sampling is usually performed from the veins in the back of the hand or anterior elbow area. The healthcare personnel first clean the area to be sampled with an antiseptic substance and then use an elastic band or various tools to put a tourniquet on the upper part of the arm. Thus, the veins from which the sample will be taken become clear. Sampling starts after the needle is inserted into the vein. When the blood starts to fill the sample tube, the medical personnel who perform the procedure open the tourniquet and after the procedure is completed, a small bandage or cotton compresses the sampled area and prevents bleeding. It is normal to have small bruises after the procedure and these conditions usually regress within a few days.

After the sample is taken, the hematocrit value is measured with a glass tube and a centrifuge device. The working principle of the centrifuge device is based on the separation of the mixed substances by using the difference in density. The container with the mixture rotates at high speed and the heavier substance is pushed towards the outside of the container, thus ensuring separation.

While the centrifugation is taking place, other cells in the bloodstream may remain among the red blood cells. This situation may cause the hematocrit value to be measured higher than normal. As a result of waiting for a long time for the blood sample to be examined, an increase in the volume of red blood cells may occur. In this case, the hematocrit value can be calculated higher than its true value.

Apart from this situation, many external factors may affect the hematocrit examination and result in the interpretation of the result as out of normal limits:

  • Living in high altitude areas
  • Pregnancy
  • Severe blood loss
  • Having a recent blood transfusion
  • Severe dehydration conditions

Before the test, it is recommended that you inform your physician about whether you have received a blood transfusion recently, which are among the factors that may affect the result, and if any, the pregnancy may be positive. The hematocrit test is not an examination associated with severe side effects or risk situations. Complaints such as bleeding or throbbing in the area where the blood sample was taken are considered normal. In the presence of any edema or ongoing bleeding despite sufficient pressure, it is recommended to seek help from health institutions.

What are the Situations where the Hematocrit  (HCT) Value Changes?

In many physiological conditions, it may cause the hematocrit value to be calculated below or above the normal limit values. Since the number of red blood cells in the bloodstream is proportional to the hematocrit value, the hematocrit is found to be low when the number of red blood cells decreases.

The hematocrit values ​​of babies in the neonatal period are high and they decrease to normal levels over time. There are also differences between genders in terms of hematocrit values, and higher values ​​are detected in men than in women. In women during pregnancy, lower hematocrit values ​​can be detected due to the increase in the amount of blood in the circulation and the decrease in its density.

The situations in which low hematocrit may occur as a finding can be summarized as follows:

  • Bone marrow diseases
  • Chronic inflammatory conditions
  • Lack of iron, folate, or vitamin B12
  • Internal bleeding
  • Hemolytic anemia
  • Kidney failure
  • Leukemia
  • Lymphoma
  • Sickle cell anemia

In people living in high altitude areas, the number of red blood cells increases to compensate for the lack of oxygen in the air. Therefore, the hematocrit values ​​of those living in high altitude areas can be determined above the normal range. Apart from this situation, hematocrit value can be detected as high in blood diseases such as severe fluid losses, congenital (congenital) heart diseases, kidney tumors, lung diseases, and polycythemia vera.

Some of the disorders with changes in the hematocrit value are as follows:

A decrease in the number of red blood cells called erythrocytes in the bloodstream due to various reasons is called anemia. This reduction may be due to slowing production or increased destruction.

Weakness, headache, difficulty concentrating, feeling cold in hands and feet, shortness of breath, and dizziness are examples of symptoms that may arise in the case of anemia.

Iron deficiency anemia is one of the most common causes of anemia. Iron is required for the production of red blood cells as it is included in the structure of the hemoglobin molecule. Deficiency may occur during pregnancy when excessive tea drinking, grain-based diet, or iron need is higher.

Blood loss is also a natural cause of anemia. While responding to rapid blood losses, it is aimed to replace the fluid volume in the circulation first. Therefore, while the amount of fluid reaches normal levels, the number of red blood cells and thus their concentration decreases. The decrease in hematocrit values ​​after blood loss returns to the normal value range within approximately 1-1.5 months.

Anemia may also occur as a result of the disorders that occur in the bone marrow, which is the production site of red blood cells. This type of anemia, which occurs due to insufficient production, is called “aplastic anemia”.

As a result of the deficiency of substances such as vitamin B12 and folic acid, which are necessary for the production of red blood cells, the production in the bone marrow slows down and the cells produced are detected larger than normal. This type of anemia is called “megaloblastic anemia”.

Vitamin B12 taken with food becomes absorbable from the intestines through a factor (intrinsic factor) secreted from the stomach and is transported to the necessary areas in the body for use in various events. In this condition, which is called pernicious anemia, a decrease in vitamin B12 absorption occurs due to a problem related to the production of this factor that allows the absorption of vitamin B12 by secretion from the stomach, and thus the production of red blood cells is negatively affected.

The lifetime of erythrocytes is approximately 120 days. Red blood cells, which carry out the duty of carrying oxygen and carbon dioxide during this period, are broken down by the spleen when their life is completed, and the molecules they contain are returned to the bloodstream to be used in the synthesis of new cells. In the presence of various congenital abnormalities in the structure of red blood cells, their destruction occurs in a shorter time. This anemia condition, in which destruction increases according to production, is known as “hemolytic anemia”.

The situations in which the total fluid volume in the blood circulation is lost for various reasons and insufficient fluid intake occurs are called dehydration. As the amount of fluid decreases, the number of red blood cells does not change, and the hematocrit value can be determined to be relatively high. This condition, which is called hemoconcentration, can also occur after burns, after excessive vomiting, and after the formation of obstruction in the intestines, apart from dehydration.

As a result of heavy exercises, the hematocrit value can be detected as high.

It refers to the red blood cell count being above its normal values. It can occur if sufficient oxygen is not taken, or it can occur during the course of malignant diseases that cause uncontrolled proliferation in the bone marrow.

If the reason for the increase in cell number occurs in response to another situation, it is classified as secondary (secondary), if it is directly related to the increase in production, it is classified as primary (primary) polycythemia.

Among the causes of secondary polycythemia, living in high altitudes and situations such as heart failure can be given as examples where cells and tissues cannot get enough oxygen.

“Polycythemia Vera”, a disease characterized by excessive blood cell production as a result of mutations in stem cells in the bone marrow, is one of the primary causes of polycythemia.

Normally, the number of red blood cells varies between 3.5-5.5 million per cubic millimeter, while the number can rise up to 7-8 million cells during this disease. The hematocrit value can be determined as 60-70%. After this increase in the number of cells in the circulation, the fluidity of the blood also decreases.

Almost 4 out of 5 patients do not have any complaints during the diagnosis of the disease. Patients with complaints usually complain of symptoms such as weakness, headache, or itching after a warm shower.

Smokers and people with chronic obstructive pulmonary disease (COPD) have a chronic (long-term) oxygen deficiency and therefore the measured hematocrit values ​​may be higher than normal.

At the same time, the change in the fluidity of the blood with the increase in the hematocrit value may cause the development of resistance in the vessels distant to the heart, and people with high hematocrit values ​​may also have high blood pressure values ​​(hypertension).

How Can Hematocrit Value Be Raised?

Treatment of low and high hematocrit can be performed by solving the problem that causes this result. In low hematocrit associated with lifestyle habits, physicians may recommend various lifestyle changes to increase the number of red blood cells. Erythrocytes, known as red blood cells, are among the most common cells in the human body. Erythrocytes, whose daily production is expressed in millions, continue to carry respiratory gas in the blood circulation for approximately 120 days after being produced in the bone marrow. Erythrocytes that complete their life span are broken down in the liver and their cellular structures are recycled so that they can be used in the production of new cells.

Iron, folic acid, and vitamin B12 are among the substances directly related to erythrocyte production. The consumption of foods with high iron content may support the body’s erythrocyte production. There are many different foods rich in iron:

  • Red meat
  • Organ meats such as kidney and liver
  • Dark green leafy vegetables such as spinach
  • Dried fruits
  • Legumes such as beans and lentils
  • Egg yolk

Folic acid belongs to the B vitamin family and is known as vitamin B9. Including foods rich in this vitamin in the nutrition plan can positively affect the hematocrit value:

  • Enriched bread or breakfast cereals
  • Green leafy vegetables
  • Legumes such as peas and beans
  • Hazelnut

Since vitamin B12 cannot be synthesized in the body, it is a nutrient that must be taken from outside with food. People who have a vegetarian diet plan, pregnant women, and women who are breastfeeding are at risk for deficiency of this vitamin, and it is recommended to follow the vitamin B12 level regularly in these people. The recommended daily intake of this vitamin, which is approximately 2.4 micrograms, enables the normal functions of the body to be supported in the production of red blood cells. There are many foods rich in vitamin B12:

  • Animal kidney and liver meat
  • Shellfish such as mussels and oysters
  • Small fish such as sardines or large fish such as tuna and salmon
  • Veal and beef
  • Breakfast cereals with enriched content
  • Milk and milk products
  • Egg

A healthy and balanced diet is an important step in bringing the hematocrit value back to normal limits. Limiting alcohol consumption and regular exercise are also among the lifestyle changes that can have a positive effect on red blood cell values. Regular exercises that can be done in the form of running, swimming, or brisk walking may also have an increasing effect on erythrocyte production in addition to their contribution to general well-being. During these physical activities, an increase in the oxygen demand of the body occurs and the brain sends various signals that erythrocytes must be produced to meet this oxygen need.



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