Diabetes in Pets

Insulin Basics[]

What is Insulin?

Insulin helps the body turn sugar into energy by sending glucose (sugar) from the blood into cells, where it is burned for energy. Insulin is the body's signal to the cells that they can accept glucose for energy. If insulin is not present, the glucose remains in the blood. For diabetics, injected (also called exogenous) insulin is needed because the pancreas is not producing enough insulin on its own.


Injected insulin is produced from the pancreas of pigs and cows, or artificially engineered or modified to match human insulin.


  • Onset is the length of time before insulin reaches the bloodstream and begins lowering blood glucose.
  • Peak is the time during which insulin is at maximum strength in terms of lowering blood glucose.
  • Duration is how long insulin continues to lower blood glucose.

These characteristics are known as the insulin's action profile.

Human Activity Profiles Various Insulins

See action profiles of common insulins in humans here

Duration [1]

  • Rapid-acting or Fast-acting insulin begins to work shortly after injection, peaks in about 1 hour, and continue to work for 2 to 4 hours.
  • Regular or Short-acting insulin reaches the bloodstream 30 minutes to an hour after injection, peaks anywhere from 2 to 3 hours after injection, and is effective for approximately 6-8 hours.
  • Intermediate-acting insulin generally reaches the bloodstream about 1-2 hours after injection, and is effective for about 8 to 12 hours.
  • Long-acting insulin generally reaches the bloodstream about 2 to 4 hours after injection, peaks 4 to 8 hours later and is effective for about 12 to 18 hours.


Injected insulins are diluted or suspended in liquid. Those dilutions/suspensions have different strengths. Most common are:

  • U-100 means 100 units of insulin per milliliter of fluid.
  • U-40 has 40 units of insulin per milliliter of fluid.

Insulin strength should be matched to the correct syringe type.


The article Insulin has more details.

Insulin subcategories are shown below, followed by a list of all insulins on this wiki.

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