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Blood collection

What is a blood test?

During a blood test, a doctor takes blood from the vascular system for examination.

Blood collection is always carried out under sterile (aseptic) conditions so that the risk of infection at the injection site is as low as possible.

When do you take a blood sample?

In addition to donating blood, blood is primarily taken to obtain information. Using the blood count, doctors can draw conclusions about illnesses or nutritional deficiencies based on the composition. Blood consists of red blood cells (erythrocytes), white blood cells (granulocytes), platelets (thrombocytes), coagulants and blood serum with proteins, electrolytes, nutrients and hormones. For example, an increase in the so-called C-reactive protein indicates an infection. In addition, an arterial blood sample can be taken as part of the gas analysis.

How does a blood sample take place?

The most common type is venous blood sampling from the crook of the elbow. The cuff, the so-called tourniquet, is placed on the arm and tightened so that on the one hand blood can collect in the veins and on the other hand you can still feel the arterial pulse. 

The doctor or the The doctor feels the best puncture site and disinfects it thoroughly. Now the vein is punctured with a needle or with the so-called butterfly system, in which the needle is also guided through two wings. The puncture through the skin may cause mild, short-term pain. Blood collection tubes are attached to the tip of the needle and a stamp is used to create a negative pressure that accelerates blood collection.

If the tube is sufficiently filled, it is removed from the needle, the stamp is bent and the tube tilted a few times. This causes the blood to combine with anticoagulants or other reagents already in the tubes rather than clumping. The most common is EDTA blood, which contains ethylenediamine tetraacetate (EDTA) in the tube. the blood components remain unbound. This is the only way the cells can be examined in the laboratory.

Finally, the doctor opens the tourniquet, pulls the needle and presses a compress on the puncture site so that no bruising occurs. A plaster protects against infections.

Do I have to appear fasting for a blood test? 

It It is important that you come to the blood test on an empty stomach so that your blood values ​​are affected as little as possible. What does fasting mean for blood draw? Basically, this means that you shouldn't eat anything eight to twelve hours beforehand. This makes it easier to compare your blood values, as food primarily influences blood sugar and blood fat values. The enzyme balance also changes as soon as the organs begin digestion.