Venepuncture for calcium assays: should we still avoid the tourniquet?

Blood was collected by venepuncture from nine healthy subjects over a ten minute period before applying a standard tourniquet, and over a ten minute period afterwards. Plasma ionised calcium was unaltered by the tourniquet, whereas total calcium, total protein and albumin in serum increased modestly. However, there was no effect on total calcium adjusted for albumin. Even without albumin adjustment the change in total calcium was negligible within one minute of the application of the tourniquet. We consider that in ordinary clinical practice, there is no need to perform venepuncture for calcium assays without a tourniquet.