The thumb is the least painful site for blood sampling in blood-glucose tests. A study has shown that obtaining blood by lancet skin puncture from the side of the thumb caused significantly less pain than lancet skin puncture from the side of the finger or venepuncture at the elbow (Lancet 1999;354:921).
The open, randomised trial of 79 patients was conducted at Manchester Royal infirmary (MRI). Dr Mark Loveland (department of emergency medicine, MRI) and colleagues say that the difference could be due to a lower density of nociceptors in the skin at the side of the thumb than in the finger. Expectation of pain from needle venepuncture, and the lack of repeat testing in the same site, were reported limitations of the study. The authors conclude: "Our study suggests that if a random blood-glucose test is needed, blood should be obtained by lancet puncture of the skin on the lateral aspect of the thumb." In addition, they comment that the results may be applicable to other circumstances where a small sample of blood is required.