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Alpha-glucosidase Inhibitors

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

Alpha-glucosidase inhibitors (AGIs) are a class of drugs used to treat type 2 diabetes (T2D). They slow down your body’s absorption of carbohydrates (carbs) after you eat. This can help reduce your blood sugar. AGIs should be combined with a healthy diet and regular exercise.

AGIs are not used as an initial treatment option. Your doctor may suggest them if other therapies do not lower your blood sugar. AGIs are useful for people at risk of low blood sugar (hypoglycemia).

How do AGIs work?

AGIs change how you digest carbs. When you eat carbs, your blood glucose levels rise. Then, insulin and other hormones remove glucose from the bloodstream. T2D causes problems with how the body uses insulin. So people with T2D have high blood sugar, especially after eating.1,2

AGIs do not change how your body uses insulin. Instead, they block enzymes in the small intestine that break down carbs into glucose. This slows the absorption of dietary carbohydrates. Delaying carb absorption slows down the rise in your blood sugar after you eat.1

Because of this, AGIs may:2,3

  • Delay T2D in those with insulin resistance
  • Reduce the risk of T2D complications, including heart problems
  • Reduce body weight
  • Increase life expectancy


Two AGIs are approved to treat T2D in the United States:1

  • Acarbose (Precose®)
  • Miglitol (Glyset®)

Acarbose is the most commonly used AGI.

What are the possible side effects?

Side effects can vary depending on the specific drug you are taking. Gastrointestinal side effects are common for AGIs. This happens because AGIs affect the digestion of some carbs. This can cause:1,2

  • Gas
  • Bloating
  • Soft stool
  • Diarrhea
  • Abdominal discomfort

A diet high in carbs seems to increase the risk of these side effects. Talk to your doctor about a healthy diet that reduces the risk of gastrointestinal problems.1,2

AGIs alone do not cause hypoglycemia. However, hypoglycemia can happen when you take AGIs in combination with certain other drugs. Look out for hypoglycemia symptoms, such as:1,2,4

  • Feeling dizzy, shaky, or lightheaded
  • Confusion or difficulty concentrating
  • Sweating
  • Heart racing or beating irregularly
  • Headache

If you notice symptoms of hypoglycemia, talk to your doctor. Ask them how to manage it.1,2

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

Other things to know

Take AGIs as your doctor prescribes. They may start you at a low dose and then slowly increase the dose. This can help reduce the risk of side effects. AGIs may be used alone or with other T2D drugs. Some drugs might increase the risk of low blood sugar while taking an AGI. Maintain a healthy diet and regular exercise while taking AGIs.1

Before beginning treatment for T2D or taking AGIs, tell your doctor your full medical history. Other drugs you take or health conditions you have may increase the risk of side effects. Also, it is not clear whether AGIs are safe for people who are pregnant or children. Talk to your doctor about:

  • Your other medicines, including over-the-counter drugs, vitamins, and supplements
  • Any other health conditions, especially inflammatory bowel disease and other intestinal problems
  • Any allergies
  • Any possibility that you are pregnant or plan to become pregnant

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