Capillary blood

The term capillary blood stands for blood from the end-flow path sections of the vascular system , the so-called hair and capillary vessels of the body. The capillary blood contains important information about the metabolic processes in the body, which is why it is taken for many laboratory tests : especially for rapid tests with test strips, for example in the case of the metabolic disorder diabetes mellitus to measure the blood sugar level or in the context of tests to determine food intolerances .

Capillary blood collection

In contrast to venous blood collection, capillary blood is only obtained from a larger blood vessel by puncturing a part of the body with good blood circulation (such as the fingertip , earlobe , heel, etc.) with a sharp sterile lancet or a special lancing device. Before this, the point to be punctured is often hyperaemized with a light massage , disinfected and then pierced about 2-3 millimeters deep, usually on the side of the distal finger bone of the third to fifth finger. One should rather not prick the touch area of ​​the fingertip, the so-called terminal touch pad, as this can be very painful. The puncture injures capillaries and smaller vessels so that blood escapes and collects at the puncture site. The leaked capillary blood is immediately applied to a test strip or a test device or taken up with a glass or measuring capillary.

Difference between capillary blood and venous blood

Venous blood and capillary blood differ in several ways. The concentration of substances in the capillary blood is subject to strong fluctuations within a short time due to changes in vascular resistance and changes in filtration. For some substances (for example amino acids , glucose, etc.), the measured values ​​in capillary blood can be somewhat higher than in venous blood, since the capillary blood has not yet completely passed through the tissue passage (quasi-arterial blood).