Factor	Effects
Site of injection	Abdominal injection (particularly if above the umbilicus) results in the quickest absorption; arm injection results in quicker absorption than thigh or hip injection.
Depth of injection	Intramuscular injections are absorbed more rapidly than subcutaneous injections.
Insulin concentration	U-40 insulin (40 units per mL) is absorbed more rapidly than U-100 insulin (100 units per mL).
Insulin dose	Higher doses have prolonged durations of action compared with lower doses.
Insulin mixing	Regular insulin maintains its potency and time-action profile when it is mixed with NPH insulin; however, mixing regular insulin with lente or ultralente insulin slows absorption and blunts the activity of regular insulin.
Exercise	Exercising a muscle group before injecting insulin into that area increases the rate of insulin absorption.
Heat application or massage	Local application of heat or massage after an insulin injection increases the rate of insulin absorption.