Following an insulin injection, there is a chemical breakdown that takes place in the body to allow it to cross into the capillaries and absorption into the blood stream.
Site for Injection
The duration of the rate of absorption of insulin is 50% longer in the thighs as compared to the abdominal wall. Regular insulin peaks at 90–120 minutes after injection in the thigh and because of subcutaneous enzymes, only about 60–65% of insulin is absorbed. Peak bloodstream levels of insulin after injection in the arm and abdomen are achieved in 75 minutes and 60 minutes respectively. The shorter time from the abdominal site also means that there is less destruction of insulin by subcutaneous enzymes.
The warmer the area the faster the absorption, the colder the area the slower the it is. A warm shower should be avoided after the injection. Going out into the cold with light clothing can lead to decreased absorption and, therefore, high blood sugar.
Exercise increases the rate of absorption of insulin by increasing the blood supply.
Recent research assuages concerns regarding shorter needle length, demonstrating that 4–5 mm length needles minimize penetration into the muscle layer and no additional leakage, even in obese patients. Glycemic control with a 4 mm needle is equivalent to that of a 5 mm or 8 mm length.
In summary, the factors that speed up insulin absorption and increase the risk of hypoglycemia are:
– Warm or hot environment, increasing blood flow to injection are
– Rubbing or massaging the area
– Injection delivered into deeper layers of skin
– Exercises increase the rate of absorption.