Before each injection, the insulin label should be verified to avoid injecting an incorrect insulin. The hands and the injection site should be clean. For all insulin preparations, except rapid- and short-acting insulin and insulin glargine, the vial or pen should be gently rolled in the palms of the hands (or shaken gently) to resuspend the insulin. An amount of air equal to the dose of insulin required should first be drawn up and injected into the vial to avoid creating a vacuum. For a mixed dose, putting sufficient air into both bottles before drawing up the dose is important. When mixing rapid- or short-acting insulin with intermediate- or long-acting insulin, the clear rapid- or short-acting insulin should be drawn into the syringe first. After the insulin is drawn into the syringe, the fluid should be inspected for air bubbles. One or two quick flicks of the forefinger against the upright syringe should allow the bubbles to escape. Air bubbles themselves are not dangerous but can cause the injected dose to be decreased.