The speed of the centrifuge is measured in rotations/revolutions per minute (RPM). Both the RPM and the radius of the centrifuge arm are used to calculate the force of gravity, from which the separation of the blood occurs within the collection tubes. Since the radius of the centrifuge arm is fixed, the speed in RPM is used to control the gravitational force required to achieve separation. Each laboratory must calculate its gravitational force for each of its centrifuges and monitor the effectiveness in achieving complete separation of blood cells from serum or plasma. A centrifuge speed that is too low could leave behind blood cells within the liquid phase, which in turn could cause false elevations in the enzymes, micronutrients, and electrolytes that are higher within the blood cells. A centrifuge speed that is too high could lead to the lysis of blood cells during separation.