Short-Acting Insulin

Reviewed by: HU Medical Review Board | Last reviewed: August 2023

People with type 2 diabetes (T2D) may need human-made insulin treatments to control their blood sugar levels. This helps prevent complications from diabetes.1,2

People with T2D make insulin but their bodies do not respond to it well. Taking an insulin treatment helps their bodies to use glucose, or sugar, to make energy. Specifically, it helps move glucose from the blood into cells. The cells then store it for later use or convert it into energy for moving, thinking, breathing, and more.1,2

Different kinds of insulin work over different time frames. Short-acting insulin is sometimes also called regular insulin. Your doctor will decide which type or types of insulin you may need to take. Your doctor will also decide which dose is right for you.1,2

How does short-acting insulin work?

Short-acting insulin should be taken about 30 minutes before eating a meal. Short-acting insulin treatments are most effective 2 to 3 hours after injection. But they will usually help lower levels of blood sugar for up to 6 hours.1,2

Short-acting insulin treatments are taken as injections (shots) beneath the skin. To reach the bloodstream, the insulin must be deposited into the fat beneath the skin.1

Examples include:3-6

  • Novolin R® (human insulin)
  • Humulin R® (human insulin)

Both of these examples are approved for use in adults and children with T2D.4,6

What are the possible side effects?

Side effects can vary depending on the specific short-acting insulin treatment you are taking.

The following side effects have been linked to short-acting insulin treatments:4,6

  • Hypoglycemia (low blood sugar)
  • Allergic reactions
  • Weight gain
  • Edema (swelling due to fluid accumulating in the body’s tissues, most noticeably in the hands and feet)
  • Hypokalemia (low levels of potassium in the blood)
  • Itching, redness, or other reactions at the place on the body where the insulin was injected

Long-term use of insulin injections, including Novolin (human insulin) and Humulin (human insulin), are associated with lipodystrophy. This is a condition where fat is lost from 1 region of the body, but gained in other regions. The risk of this can be minimized by rotating injection sites regularly.4,6

It is possible to develop a severe, life-threatening allergic reaction from short-acting insulin treatments. This is called anaphylaxis. It is a whole-body reaction. Symptoms of anaphylaxis include:3-7

  • Swollen tongue or throat, airway closing, trouble breathing
  • Hives and itching
  • Flushed (red-looking) or pale skin
  • Sudden drop in blood pressure
  • Rapid, weak pulse
  • Nausea or vomiting

If you experience any side effects that could be life-threatening, call 9-1-1 right away.

These are not all the possible side effects of short-acting insulin. Talk to your doctor about what to expect when taking a short-acting insulin treatment. You also should call your doctor if you have any changes that concern you when taking a short-acting insulin.

Other things to know

Short-acting insulin treatments should not be taken when blood sugar levels are lower than normal.3-6

Never share needles or syringes with another person. Doing so increases your risks for getting or sharing an infectious disease.4,6

Before beginning treatment for T2D, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you take. This includes over-the-counter drugs.

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