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Insulin Action

Insulin is a medicine that lowers blood glucose (sugar).  There are several types of insulin.  Each type of insulin has a certain time period in which it works.  In order to understand insulin action, it is helpful to know the onset, peak and duration of the insulin you take.

  • Onset refers to when the insulin starts to work.
  • Peak refers to when the insulin works hardest.
  • Duration refers to how long the insulin works.

You are more likely to have a low blood glucose when your insulin is peaking, during periods of increased physical activity or if you are eating less food.   If you are having problems with low blood glucose, talk to your healthcare provider about adjusting your insulin. 

Usual Action Times of Insulin


Lispro (Humalog)

Aspart (Novolog)

Glulisine (Apidra)

0-15 min before meal 10-30 min 30 min - 3 hours 3-5 hours

Regular (R)


30 min before meal 30-60 min 2-5 hours Up to 12 hours



Does not need to be given with meal 90 min - 4 hours 4-12 hours Up to 24 hours
Long Acting

Glargine (Lantus)

Detemir (Levemir)

Does not need to be given with meal 45 min - 4 hours Minimal Up to 24 hours

Page last updated: November 07, 2019