Alpha-glucosidase inhibitors (AGIs), sometimes referred to as starch blockers, are anti-diabetic medicines that help to reduce post meal blood glucose levels

Unlike most other types of diabetes drugs, they don’t have a direct effect on insulin secretion or sensitivity. Instead they work by slowing down the digestion of carbohydrates found in starchy foods.

Drugs in this class

Examples of alpha-glucosidase inhibitors include:

*Brand names in brackets.

In the UK only Acarbose is available. The diabetes pill can be either chewed with the first bite of a meal or swallowed whole with some water immediately before the meal.

It is normally used as single treatment, but in some cases can be taken in combination with a sulphonylurea

How do alpha-glucosidase inhibitors work?

AGIs slow down digestion by blocking enzymes in the small intestine that break down carbohydrates.

By blocking these enzymes, the medication can slow down the digestion of carbohydrates in the small intestine so that glucose from food enters the bloodstream more slowly, thus reducing the rise in blood glucose levels after eating.

Who are alpha-glucosidase inhibitors suitable for?

Alpha-glucosidase inhibitors are suitable for people with type 2 diabetes with difficulty controlling blood glucose levels following meals.


AGIs have benefits in reducing post meal blood sugars and therefore helping to lower HbA1c, particularly when used in combination with other diabetes medication.

They also raise post meal levels of GLP-1, a hormone which helps to delay digestion and decreases appetite.

This means they do not increase the likelihood of weight gain, unlike sulphonylureas and thiazolidinediones

Side effects

Due to the function of alpha-glucosidase inhibitors, gastrointestinal side effects such as:

  • Flatulence (wind) and
  • Diarrhoea are common problems for users.

However, these effects usually reduce as your body adjusts to the medication.

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