Fingerprick

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In medicine, some blood tests are conducted on venous blood obtained by fingerprick. There are various ways of opening a small wound that produces no more than a few drops of blood. The procedure can be painful, but may be quicker and less distressing than venipuncture.

After a droplet has formed, venous blood is sucked up by a capillary (a thin glass tube), usually passively or sometimes by indirect suction.

Tests commonly conducted on capillary blood are:

glucose levels - diabetics often have a portable blood meter to check on their blood sugar.
hemoglobin levels - fingerprick testing of hemoglobin is a quick screening procedure to check if a blood donor or plasma donor has a high enough blood count to be allowed to donate blood or blood components.

Fingerpricks are sometimes done on children and the elderly, when only a small amount of blood (less than 500 μg) is needed for a test. Neonates (newborn babies) are given heelpricks instead, as this is less likely to cause permanent damage (and because babies have very small fingers).