The normal range of endogenous insulin in non-diabetics is between 60 to 100 milligrams per deciliters when they first wake up in the morning, according to Diabetes Education Online. The normal range is less than 140 milligrams per deciliters after a meal.
Overnight, insulin is secreted slowly and steadily by the pancreas, explains Diabetes Education Online. The levels spike just after breakfast, and then drop. They spike again, but not as dramatically, after lunch. Insulin levels spike, again dramatically, after the evening meal. These spikes just after meals allow the body to break down and use the carbohydrates and sugars that are in the food.