Squeezing finger for blood

When you squeeze your finger after pricking it, your body detects that you have a hole in it, and releases a chemical to plug the hole to stop the leak, which can then contaminte the blood sample.

Some thing I had long forgot about until the other day when ordering a new meter and it cropped up in the conversation with the company.

If you have trouble getting blood from your finger wash your hands in warm water first, this will encourage more blood to flow to your fingers.

Blood obtained via skin puncture is a mixture of undetermined proportions of blood from arterioles, venules, capillaries, plus interstitial and intracellular fluids. For BG testing, you want as good a supply of capillary blood as possible. If you look down this page your will see a section entitled Top 10 Keys to Obtaining a High Quality Capillary Blood Specimen

http://www.bd.com/vacutainer/labnotes/Volume20Number1

As Pav states, your blood platelets help clot the blood, sometimes quickly, so this is one problem. http://en.wikipedia.org/wiki/Platelet