Thick blood causes symptoms and treatment medical practice

Thick blood describes an above-normal concentration of red blood cells (erythrocytes), which can pose serious health problems. (Image: fotomek/

What is colloquially called "thick blood" is actually medically correctly called polyglobulia or erythrocytosis and describes a concentration of red blood cells (erythrocytes) in the blood that is above the normal level. For health, this can mean serious problems, because the excess of erythrocytes actually compacts the blood, which enormously impairs its flow properties. This can result in vascular diseases such as thrombosis. be bottlenecks in the oxygen supply of the body. The risk of heart attack or stroke also increases enormously due to erythrocytosis.


Our blood is the main supply fluid of our body and consists of a 90-percent aqueous solution, in which the following substances are significantly present:

– red blood cells (erythrocytes), – white blood cells (leukocytes), – blood plasma, – protein (proteins), – salts.

In addition, there are other substances in the blood which, although they are only present on a molecular level, reflect the many different functions that the blood has in the body. Roughly, these tasks can be divided as follows:

– Transport of substances: The main task of the blood is to transport important substances to their place of use in the body, including nutrients, oxygen and even hormones. The erythrocytes are responsible for transporting oxygen, binding the oxygen molecules from the lungs and releasing them only at their destination in the organism. At the same time, the blood is also involved in the removal of metabolic waste products, including carbon dioxide and urea. Immune defense: The leukocytes found in the blood are an essential component of the immune system. If the health is attacked by foreign bodies (z.B.B. bacteria or viruses) to combat them. This takes place in several steps, which, in addition to foreign body analysis, also includes the production of antibodies. In addition, the coagulation function of blood is an important part of the body's defense against injury, because blood coagulation closes wounds and thus prevents germs from entering the wound opening. – Heat regulation: Due to the continuous flow of blood through the body, it also becomes a heat conductor. Thanks to the blood circulation, the body temperature can also be regulated. It regulates both the body's own heat and excess heat acting on the organism from the outside.

Erythrocytosis can now have dangerous effects on all of the above functions. The cause of formation is an increased formation of new blood, which significantly increases the number of erythrocytes in the blood. An increased number of erythrocytes becomes clear in the so-called hematocrit value (percentage of blood cells in the blood). This is normally between 37 and 45 percent for women and 42 to 50 percent for men. In case of erythrocytosis, the value is significantly increased. Is visibly more than 50 percent. The change in consistency of the blood actually makes it thicker. Can only perform its functions to a limited extent, if at all. Above all, circulatory disturbances and associated accompanying symptoms are typical of blood thickening and can be accompanied by visible signs of oxygen deficiency (v.a. cyanosis) to organ failure due to insufficient oxygen supply. Particularly dangerous in this respect are disorders of heart and brain function. The causes of erythrocytosis are many and varied. Can be physiological or pathological in nature. Physiologically, the mechanisms of formation of red blood cells play a predominant role. Their presence in the blood is normally regulated by the hormone erythropoietin (EPO for short), which is produced in the kidney. Since erythrocytes are responsible for oxygen transport in the blood, the hormone is also controlled by the oxygen content of the blood. If there is too little oxygen in the blood over a longer period of time, the hormone reacts by stimulating the production of erythrocytes in the bone marrow.

The proportion of red blood cells is normally regulated by the hormone erythropoietin (EPO for short, shown schematically in the picture), which is produced in the kidney. (Image:

In the event of a persistent lack of oxygen in the blood (hypoxemia), the body first tries to compensate for the oxygen level by producing more erythrocytes. So, erythropoietin increases, which increases the rate of red blood cell production, which subsequently leads to physiologically induced erythrocytosis. Various influencing factors can be responsible for such bodily processes. A longer stay in an oxygen-poor environment is conceivable, for example. This occurs in particular during stays at high altitudes of over 4000 meters.

Persistent smoking can also cause erythrocytosis. The reason for this is the fact that the carbon monoxide contained in cigarette smoke blocks the oxygen binding sites of the erythrocytes and as a result they can bind less oxygen. The oxygen level of the blood is reduced in the long term by this disorder. Among the causes of the disease, cardiac diseases such as heart failure or valvular heart disease and pulmonary diseases such as bronchial asthma, COPD or emphysema are often responsible for hypoxemia.

Speaking of EPO: Researchers in Switzerland have recently achieved a breakthrough in causal research into the development of autosomal-dominant inherited erythrocytosis. The test subjects were members of a family in which about 50 percent of all male and female members suffered from thick blood over four generations. The cause was found to be a genetic defect that caused a mutation in the EPO gene.

Tumor diseases and blood oxygen levels

Another factor that can cause erythrocyte production to overshoot is cancer of the hematopoietic system. Osteomyelofibrosis, for example, can be mentioned here. This is a malignant disease of the bone marrow in which cell degeneration leads to a steady transformation of bone marrow components into connective tie (fibrosis).

Cushing's disease, a tumor disease of the pituitary gland, cannot be ruled out as a cause of erythrocytosis. The disease has an increased stimulation of the adrenal cortex. This results in an increase in cortisone secretion. Cortisone, for its part, stimulates the production of red blood cells in the bone marrow. The same applies to various forms of kidney tumors, which trigger similar disturbances in erythrocyte formation. Last but not least, blood cancer is of course also a disruptive factor that can significantly impair the formation and functionality of red blood cells.

Thromboses caused by the thickening of the blood also pose a high risk. The latter develop all too readily in the context of erythrocytosis, since the blood flow slows down due to the thickened blood and thus causes blood congestion in the veins. All in all, further secondary complaints are to be expected as a result of the disease.

Other causes

Factors such as massive vomiting and persistent diarrhea are underestimated when it comes to thick blood. The associated loss of fluid in the body greatly reduces the relative proportions of liquid blood components in the long term, which can alter the material concentration of the blood so that red blood cells become predominant. Frequently associated with severe nausea and incessant vomiting are gastrointestinal infections, poisoning and food intolerances.

Influencing factors such as massive vomiting and persistent diarrhea are often underestimated, but are a possible trigger for thick blood due to fluid loss. (Image: Doris Heinrichs/

An increased supply of the erythrocyte-forming hormone erythropoietin from outside cannot be ruled out as a cause of the disease. This is mainly due to doping with preparations such as EPO or androgens. A relatively rare cause of the disease is the so-called fetofetal transfusion syndrome – a circulatory and nutritional disorder that occurs exclusively in identical twins in the womb and causes a reciprocal exchange of blood between the children. A substance imbalance in the blood of the affected twins is relatively probable in the context of this syndrome.


Symptoms in erythrocytosis mainly include consequences resulting from insufficient oxygen transport of the blood. For example, persistent fatigue and headache are typical consequences of oxygen deprivation. Cyanosis, a blue discoloration of body parts due to oxygen-depleted and therefore darkly discolored blood, is also considered to be generally typical. Especially the extremities are. Acras as distal limbs are particularly affected by cyanosis.

Respiratory problems and thrombosis caused by thickening of the blood also represent a high risk. The latter develop all too readily in the context of erythrocytosis, as the blood prere rises rapidly due to the thickened blood and thus causes blood congestion in the veins. Overall, the following symptoms can be expected due to the disease:

– headache, , , – increased risk of thrombosis, – cyanosis, – metabolic disorders, – feeling of shortness of breath, – organ dysfunction.

Caution: If left untreated, erythrocytosis can lead to severe functional disorders of the heart and brain. The risk of stroke and heart attack increases enormously as a result! Pulmonary embolism can also be the result of untreated blood thickening.


Diagnosis is made in case of thick blood by laboratory analysis of blood samples. In addition to the hematocrit value, the most important laboratory parameters here are the hemoglobin values and the oxygen saturation in the blood vessels. Depending on the focus, further diagnostic procedures include sonographic procedures and cardiodiagnostic procedures (z.B. ECG and heart ultrasound) on. If a tumor is suspected, imaging procedures such as CT or MRI are also used. Blood sample for laboratory chemical determination of thick blood. In addition to the hematocrit value, the most important laboratory parameters here are hemoglobin values and oxygen saturation in the blood vessels. (Image: Henrik Dolle/


Therapeutic measures against erythrocytosis depend entirely on the underlying cause. If this is due to a genetic defect, there are unfortunately hardly any possibilities to completely cure the disease. For most other influencing factors, however, very good treatment options now exist.

Targeted fluid intake

If the percentage of erythrocytes is only relatively increased because there are too few liquid components in the blood, the therapy consists of the supply of physiological liquid solutions via the vein. Patients should also drink plenty of fluids during therapy to restore their body's fluid balance back to normal. Such measures are particularly necessary in the case of diarrheal diseases such as gastroenteritis.

Oxygen therapy

If the erythrocytosis is due to a hypoxic state, the first measure is usually a supply of high-dose oxygen from the outside. Following this, the actual underlying disease must be treated, which in the case of heart and lung disease often proves to be very lengthy, but is not completely impossible. If smoking was involved in the development of hypoxemia, the therapy measures introduced naturally aim at permanent abstinence from cigarettes. Support can be provided by appropriate smoking cessation programs as an accompaniment to therapy.

Drug and radiation therapy

Tumor diseases as a cause of the thick blood usually require chemotherapeutic treatment with drugs. Blood cancer in particular cannot be treated surgically, but requires a combination therapy of cytostatics and radiotherapy. Promising drugs here include drugs such as chlorambuzil, which is now often administered together with the antibody obinutuzumab in the case of leukemia. In addition, gene therapies are reporting increased success in the fight against blood cancer. Complementary blood thinning agents may be administered for erythrocytosis.

Hemodilution therapy

The term hemodilution therapy is the technical term for bloodletting. This involves taking 300 to 500 ml of blood at regular intervals. Replaced by physiological fluid solutions. The aim is to bring the hematocrit back into the physiological normal range through bloodletting. The therapy is usually an emergency solution for cases that cannot be treated in any other way. This applies, for example, to genetic defects in the EPO gene, but also to untreatable cancers.

Diseases as cause of thick blood: hypoxemia, blood cancer, Cushing's disease, renal tumor, osteomyelofibrosis, bronchial asthma, COPD, pulmonary emphysema, fetofetal transfusion syndrome, gastrointestinal infection, poisoning.(ma)

– Merck& Co., Inc.: Secondary erythrocytosis (secondary polycythemia) (Retrieved: 16.07.2019), – Herold, Gerd: Internal Medicine 2019, self-published, 2018 – Siegel, Fabian P. / Petrides, Petro E.: Congenital and acquired polycythemias, Dtsch Arztebl, 2008, aerzteblatt.en – Mayo Clinic: Polycythemia vera (retrieval: 16.07.2019), – Genetic and Rare Diseases Information Center (GARD): Polycythemia vera (retrieval: 16.07.2019), – National Organization for Rare Disorders (NORD): Polycythemia Vera (retrieval: 16.07.2019), – National Heart, Lung, and Blood Institute: Polycythemia Vera (retrieval: 16.07.2019), – mpn network e. V. c/o German Leukemia-. Lymphoma support e. German Leukemia-. Lymphoma help e. V.Polycythaemia vera (PV): Frequently asked questions (retrieval: 16.07.2019), mpn network. This article contains only general information. May not be used for self-diagnosis or self-treatment. It cannot replace a visit to the doctor.

D64, D75 ICD codes are internationally valid codes for medical diagnoses. They are found z.B.

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