Blood count and blood group · Blood

Hematocrit (Ht)

The share of the blood that consists of red blood cells; moves along with the hemoglobin and reacts strongly to the fluid balance.

At a glance

Measured in blood
In 15 test panels
No special preparation

Explanation

Hematocrit (Ht): what is measured?

Hematocrit is the percentage of the blood volume taken up by red blood cells; with a hematocrit of 40%, 100 milliliters of blood consists of 40 milliliters of red blood cells. The value depends on the number of red blood cells, their size and the amount of fluid (plasma) in the blood. Hematocrit and hemoglobin almost always move together; the result is therefore compared with the hemoglobin, the red blood cell count and the MCV.

What can it detect?

Anemia, together with the hemoglobin
Dehydration or, on the contrary, dilution of the blood (for example during pregnancy)
Too many red blood cells (polycythemia) due to smoking, a lung disease, altitude or, rarely, a bone marrow disease

Result

What does the result mean?

Hematocrit (Ht) too high

A raised hematocrit is usually due to dehydration: there are then not more blood cells, but there is less fluid. This happens with not drinking enough, diarrhea, fever, heavy sweating or water tablets, and recovers once fluids are replenished. If the value stays high, the body may be making extra red blood cells in response to a lack of oxygen: with smoking, a lung disease, sleep apnea or a longer stay at high altitude. Testosterone use also raises the hematocrit. Rarely, there is a bone marrow disease (polycythemia vera) in which too many red blood cells are made; the blood then becomes thicker and the chance of thrombosis rises.

Hematocrit (Ht) too low

A low hematocrit fits anemia and has the same causes as a low hemoglobin: iron deficiency, a shortage of vitamin B12 or folic acid, a chronic disease, bleeding or accelerated breakdown of red blood cells. A slight decrease can also be due to dilution: during pregnancy the blood volume increases considerably, and drinking a lot shortly before the blood draw or an IV drip has the same effect. Symptoms that go with anemia are tiredness, shortness of breath on exertion, dizziness and paleness. With a low hematocrit, the GP always looks at the hemoglobin, the MCV and the ferritin.

After an abnormal result

With a low hematocrit, the GP follows the Dutch GP guideline (NHG) on anemia: measuring the MCV and the ferritin and, if needed, further testing into the cause. With a raised hematocrit, the measurement is usually repeated after drinking well; if the value stays high, the GP looks at smoking, lung function, sleep apnea and medication, and with a strongly raised value refers to an internist (specialist in internal medicine) or hematologist.

Reliability

How reliable is the test?

In modern blood cell counters, hematocrit is not measured separately but calculated from the number of red blood cells and their average size; the value is technically reliable and closely follows the hemoglobin. Anemia is diagnosed with the hemoglobin; because the hematocrit almost follows the hemoglobin, it adds little to it. With a raised value, the fluid balance at the time of the blood draw is the main disturbing factor.

What can affect the result?

Dehydration raises the hematocrit; drinking a lot, a pregnancy or an IV drip lowers it, without a change in the number of red blood cells.
Lying down for a long time lowers the value, and standing for a long time or a tight tourniquet raises it, by a few percent.
Smoking, staying at altitude and testosterone use raise the hematocrit.
When blood is in transit to the laboratory for a long time, the red blood cells swell slightly, so the hematocrit comes out higher.

Who it is for

Who is the test useful for?

Useful for

Useful as part of the blood count with symptoms that fit anemia, for monitoring known anemia and in people who use testosterone, smoke or have a lung disease, because too high a hematocrit is a point of attention there. As a single value it adds little to the hemoglobin; in healthy adults without symptoms, a slightly raised value is usually due to not drinking enough before the blood draw.

How common is it?

In general practice, anemia is diagnosed in about 9 in 1000 people per year, especially in women between 15 and 50 years of age and in older people. A raised hematocrit due to dehydration or smoking is common; polycythemia vera, a bone marrow disease with too many red blood cells, is rare and is mainly found at older age.

The NHG guideline on anemia (M76) and NVKC

Drawbacks and risks

A slightly raised hematocrit due to not drinking enough before the blood draw is the most common abnormality and, without a repeat measurement, a source of unnecessary worry.

Get tested

Hematocrit (Ht): test panels

Hematocrit (Ht) is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.

Blood draw
Vegan Test
Panel for vegetarian or vegan diet; B12 D iron and more.
€ 116,00
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General Health Checkup
With this General Health Check-up, you gain detailed insight into your overall health and well-being.
€ 125,00
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Blood Count
Blood Count; complete analysis of blood cells for detection of anemia and infections.
€ 19,00
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Complete Blood Count (CBC)
Complete Blood Count Extended; standard blood count plus detailed white blood cell analysis.
€ 27,00
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InsideTracker
InsideTracker Blood Analysis: analyze 48 biomarkers for complete health optimization and personalized recommendations.
€ 335,00
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Testosterone Replacement Therapy (TRT)
Testosterone, LH, FSH, Oestradiol, Prolactin, liver function, and blood values. For men with low testosterone or TRT monitoring.
€ 175,00
Blood draw
Endurance Sports
Complete blood count, iron status (ferritin, transferrin), kidney function, liver function, testosterone, and hs-CRP. For athletes and endurance sport participants.
€ 203,00
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Vegetarian Extensive
Iron, ferritin, B12 total and active, vitamin D, folic acid, zinc, magnesium, hemoglobin, and hematocrit. Complete nutritional status check.
€ 269,00
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Comprehensive Fatigue Test
Vitamin D, B12, TSH, fT4, glucose, MCV, ferritin, ESR and complete blood count. For persistent fatigue with inflammation check.
€ 152,00

How reliable is the test?

Hematocrit (Ht)