Last reviewed by: Aleksey Portnov , medical expert, on 01.06.2018

Hematocrit is volumetric fraction of erythrocytes in whole blood (the ratio of the volume of red blood cells and plasma). Hematocrit value depends on the number and volume of erythrocytes. Ht-settlement (secondary) parameter output from the number of red blood cells and its volume (Ht = RBCxMCV) with hematology cell counters.

Hematocrit is a specific percentage balance indicator of the volume of erythrocytes and plasma in human blood.

Why is it important to determine the hematocrit?

Erythrocytes, or so-called red blood cells, contain the "breathing" protein (hemoglobin). Hemoglobin plays an important role in the nutrition of the tissues, as it is the "transport" for oxygen, besides, it accelerates carbon dioxide output. Ideally, the blood contains about sixty percent of the specific liquid or plasma, and the rest is comprised of the proteins; white cells or leukocytes, flat blood platelets or thrombocytes and erythrocytes itself. Hematocrit is a norm ratio of red cells that predominate in the blood (up to 99%) up to plasma or deviation indicator from the indicated standards. Thus, we can say that the hematocrit shows how well erythrocytes operate the respiratory function.

What for to determine hematocrit value?

Set of pathological conditions, diseases, require comprehensive examination, detailed laboratory tests which have specific indicators of blood. This helps to specify the diagnosis and start the effective treatment. Any competent doctor wouldn’t be satisfied only with the information of defining a hemoglobin level, more likely the doctor would prescribe a multifactorial research. Hematocrit is essentially nothing more than information and indicators of common volume of erythrocytes but not their number, so, like a puzzle in the overall picture, it complements the assessment of red blood cells. In conjunction with the color marker, hemoglobin level, and other information or indices, hematocrit can complement and complete diagnostic system, which helps doctor to correctly interpret the clinical study of blood. An abnormal hematocrit shows changes in the erythrocyte system, which in turn signals about diseases such as cardiovascular disease, anemia, oncopathology, diseases of gastro-intestinal system.

How to Conduct a Hematocrit analysis?

Hematocrit isn’t only the part of the complete blood count information, but also a glass capillary, a tube, similar to a small pipette. Device has a clear division (one hundred equal parts). Blood has been taken from a vein with a needle for this analysis, the blood of babies taken with a lancet, it’s less traumatic. Glass hematocrit filled with material for research is placed for an hour or an hour and half into a special centrifuge. Under the action of centrifugal turns (1.5 thousand times a minute) erythrocytes begin to settle to the bottom of the hematocrit capillary below a certain level, so that is the informative indicator.

How to calculate the hematocrit and what is its norm?

A conditional normal level for women is between 35% and 42%; men have another indicator (from 40% to 47% and more; up to 52%). Babies from one to five years may have hematocrit lower than adults by 8-10%, but for newborn babies, on the other hand, increased by 20% hematocrit is permissible norm.

What does the hematocrit determine?

If we simplify, the hematocrit is the indicator of high or low blood density level. Of course, hematocrit sign is interpreted with much more serious and specific scheme and denoted low or normal (within the confines or lowered).

If the percentage is higher than normal numbers, there is reason to talk about the threat of erythrocytosis. Erythrocytosis is a significant increase of red blood cells number in the blood composition, which in turn requires further diagnosis. Increased hematocrit can also be the signal of erythremia, which is an extremely serious disease. Due to erythremia erythrocytes rapidly begin to increase in the number in the most important area of hematopoiesis (the bone marrow). In addition, hematocrit above the normal level may be during the latent, hidden or acute hypoxia (oxygen starvation), or during polycystic kidney disease or tumors in its. Leukemia, peritonitis, thrombosis, diabetes, burns and even banal sweating can result in increase of hematocrit index.

Lowering of hematocrit level is typical for almost all kinds of anemia; it may be due to poor kidney function. Below normal hematocrit level may also be due to the high blood loss associated with injuries or surgery. It should be noted that pregnant women hematocrit level drops in the last (third) trimester for obvious reasons. More terrible diseases, such as cancer, including blood disorders (myelogenous leukemia, hemoblastosis) are also accompanied by reduced hematocrit level.

You should not panic while self-studying the results of the clinical analysis of blood, because this information is not a definitive diagnosis. If the hematocrit doesn’t fit the normal limit, it does not mean that you have a deadly disease. The volume of erythrocytes, as well as its correlation to plasma, is only a part of the overall clinical picture, rather than a direct pointer to the disease. In short, hematocrit and its decryption are subject only for competent professionals who will take into account all parameters of hematological studies in the aggregate.

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