Samuel Grossman, BS Pharm, Pharm.D, CDE Answered 7/2/2015

Injecting insulin in the thigh when you swim or dive, can increase the absorption of insulin from the injection site and potentially lead to low blood sugar levels. In my practice, I recommend to individuals that they inject pre-meal rapid acting insulin to wait 15-30 minutes after the injection before going swimming. The wait time ensures that insulin is absorbed from the injection site and may lead to reduction in potential incidents of low blood sugar levels while swimming or diving.