What is the normal range of hematocrit

Hematocrit

Abbreviations: Hkt, Hct, HK
English: hematocrit

1 definition

As Hematocrit is the term used for the volume fraction of cellular elements in the blood. With 96%, erythrocytes make up the largest proportion. The hematocrit is usually given in%. The SI unit is liter per liter (l / l). The hematocrit is part of the small blood count.

see also:Platelet hematocrit

2 method

Classically, the hematocrit is determined by centrifugation of an anticoagulated whole blood sample, usually EDTA blood, in a very slim container, the hematocrit capillary. There are or have been special hematocrit centrifuges for this purpose. The capillary is then placed on a scale and the proportion of sediment (the cellular components) in the total volume is measured. This reference method is rarely used in routine work.

Hematology devices calculate hematocrit by multiplying the MCV by the number of red blood cells. This is the reverse of the classic approach, in which the MCV is calculated from the hematocrit divided by the erythrocyte count.

The hematocrit can also be determined by measuring the conductivity of the whole blood sample. BGA devices, for example, work with this method.

3 reference range

Different reference ranges or normal values ​​are given for the hematocrit, depending on the source:

  • Men: 43-49% (also: 40-52%)
  • Women: 37-45% (also: 37-48%)

In case of doubt, the reference range given by the laboratory is decisive for the assessment.

4 etiology

A high hematocrit can, for example, result from a high proportion of erythrocytes in the blood (doping, altitude adjustment, lung diseases, heavy smoking) or dehydration of the patient. A low hematocrit can be caused by erythropoiesis disorders, chronic kidney failure (lack of erythropoietin) or volume therapy (e.g. by administering saline infusions instead of blood reserves in the event of blood loss).

5 background

In Anglo-Saxon countries and in intensive care medicine, the hematocrit is sometimes used instead of the hemoglobin concentration as a measure, e.g. for anemia. Both parameters make the same statement, but using different measurement methods. Multiplying the hemoglobin concentration by a factor of 3 gives an approximate hematocrit (in%).

In the case of hyperacute blood loss, the hematocrit and the hemoglobin concentration do not change, although the patient may be bleeding to death because the body (or the doctor) does not have time to replace the missing volume with fluid.