When does NPH insulin peak?

NPH insulin peaks between four and nine hours after injection, according to Diabetes Mall. NPH insulin starts working in one to three hours from injection, and its effectiveness ends in 14 to 20 hours.

NPH insulin has a shorter acting time than Lantus but a longer peak time, according to Diabetes Mall. It is also less expensive than Lantus. Three well-timed shots of NPH can work much like Lantus. NPH insulin can provide a diabetic with a stable basal insulin action when the total dose has been dialed in. NPH insulin is especially useful in those who experience the dawn phenomenon, a rise in blood sugar levels during the early morning hours.