Alpha-Glucosidase Inhibitors (AGI) for Type 2 Diabetes

Alpha-glucosidase inhibitors (AGIs) are oral diabetes medications that slow down the absorption of carbohydrates in your digestive system. Your healthcare provider may prescribe them if your blood sugar spikes after meals. These drugs can control blood sugar, but you may experience gastrointestinal side effects. Discuss with your healthcare provider whether they are right for you. 

This article discusses how AGIs work, their side effects, and warnings to be aware of.

Doctor handing man prescription in doctor's office

Jon Feingersh Photography Inc / Getty Images

What Are Alpha-Glucosidase Inhibitors?

AGIs are drugs used to manage blood sugar spikes following a meal. There are two types available:

  • Acarbose, under the brand name Precose or Prandase
  • Miglitol, under the brand name Glyset

How They Work

AGIs decrease the action of enzymes known as alpha-glucosidases. These enzymes break down carbohydrates within the digestive system and convert them into glucose (sugar) for energy. When the enzyme is blocked from doing its job, fewer carbohydrates are turned into sugar.

If a person deals with blood sugar spikes following a meal, AGIs can slow the conversion of carbohydrates into glucose, which limits the amount of glucose that gets into the bloodstream.

What are Monosaccharides?

Monosaccharides are the most basic form of carbohydrate, also referred to as simple sugars. When you eat foods containing carbohydrates, they are broken down into monosaccharides by the digestive system and increase the amount of glucose in the blood. That glucose can be transferred into cells to be used for energy.


The AGI dosage differs depending on the type taken. Miglitol is typically started at a low dose of 25 milligrams (mg) three times per day and gradually increased to 50 or 100 mg three times daily. Sometimes, a person may start with a once-daily dose of 25 mg to avoid harsh side effects. These medications must be taken with food, preferably at the very first bite of a meal. 

Acarbose has the same dosing of 25, 50, or 100 mg but is slightly different from Miglitol because weight affects how much a person should take. People of all weights will begin with either 25 mg once a day or thrice a day and gradually increase. However, if a person weighs under 132 pounds, they can only take a maximum of 50 mg three times per day. If they weigh over that amount, they can take as much as 100 mg three times daily.

Side Effects

AGIs come with several side effects, some of which are mild and others more severe. Some common and mild side effects include:

  • Flatulence
  • Bloating
  • Abdominal discomfort
  • Diarrhea
  • Skin rash or hives

How Long Will I Have to Deal with Mild Side Effects?

The mild gastrointestinal side effects, such as gas and diarrhea, usually lessen or disappear within a few weeks of starting the medication.


While taking AGIs, monitoring blood sugar levels is important because the medication can cause excessively low blood sugar (hypoglycemia) in people that take them alongside other diabetes drugs.

Symptoms of hypoglycemia include:

  • Shakiness
  • Dizziness
  • Lightheadedness
  • Nervousness or irritability
  • Changes in mood or behavior
  • Headaches
  • Tingling or numbness around the mouth
  • Pale skin
  • Weakness
  • Hunger
  • Jerky or clumsy movements
  • Confusion
  • Seizures
  • Loss of consciousness

Your blood sugar level is low if it falls below 70 milligrams per deciliter (mg/dL). However, that doesn’t mean you must rush to the emergency room.

If you notice your level is low, you can try to raise it by eating 15 grams of carbs to see if it reaches your target range. If that doesn’t work and you notice your blood sugar level continually dropping, it indicates that you are on your way to dangerously low blood sugar levels.

What Constitutes a Hypoglycemic Medical Emergency?

If your blood sugar level drops below 55 mg/dL, you should contact an emergency medical provider. They will give you instructions on what to do and if you need to go to the hospital. Notify your caregiver or loved ones to call 911 immediately if you:

  • Lose consciousness
  • Are displaying signs of confusion
  • Have a seizure
  • Anytime they may be worried about severely low blood sugar

Contraindications and Warnings

There are some health risks associated with the use of AGIS. They include:

  • GI disease: People who have inflammatory bowel disease, colonic ulceration, an increased risk for bowel obstruction, or a disorder that hinders digestion should avoid this medication.
  • Liver problems: In some cases, AGIs can cause an issue with how the liver functions leading to jaundice (yellowing of the skin or eyes) or hepatitis. People with cirrhosis of the liver or other liver diseases should not take AGIs.
  • Chronic kidney disease: Although some research has found that people with chronic kidney disease can take AGIs, tell your healthcare provider if you have kidney issues before starting this medication.


AGIs are medications used as additional therapy for people with diabetes. They are designed to help lessen blood sugar spikes following a meal by reducing how many carbs are broken down into sugar in the body. While the drug is safe and can help people manage their blood sugar effectively, it has some side effects. They are usually mild and can include diarrhea, bloating, and flatulence. Typically, these side effects disappear within a few weeks of starting treatment.

People taking AGIs must monitor their blood sugar levels regularly to ensure they do not develop dangerously low blood sugar due to a lack of carb absorption. By doing so, they can avoid severe health repercussions. Those with GI or liver disease should avoid treatment with AGIs.

A Word From Verywell

Having diabetes isn’t always easy, but many medications are available to help you manage your blood sugar levels. If you notice your blood sugar always spikes after a meal, speak to your healthcare provider about AGIs. While they are not appropriate for everyone, they could be a supplemental treatment option to help keep your after-meal spikes at bay.

Frequently Asked Questions

  • Do I take alpha-glucosidase inhibitors with other diabetes drugs?

    AGIs are supplemental therapy. That means they are not meant to treat diabetes alone but alongside other methods. AGIs do not lower your blood sugar. They only inhibit the absorption of certain foods during mealtime, so you don’t experience a spike.

  • Can you eat carbohydrates if you take agi diabetes drugs?

    When it comes to AGIs, eating carbohydrates is allowed. The drug reduces your body’s ability to process them into glucose. You do not have to eliminate carbs from your diet while on the medication.

  • Can you prevent stomach pain when taking alpha-glucosidase inhibitors?

    Stomach pain, along with other gastrointestinal issues, is a common side effect associated with taking AGIs. While it’s not easy to avoid, there is good news. The side effects typically occur at the beginning of treatment with AGIs and subside within a few weeks after the body has adjusted to the new medication.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. MedlinePlus. Miglitol.

  2. Medline Plus. Acarbose.

  3. UpToDate. Alpha-glucosidase inhibitors for treatment of diabetes mellitus.

  4. DailyMed. Acarbose tablets.

  5. Liver Tox: Clinical and Research Information on Drug-Induced Liver Injury. Alpha-glucosidase inhibitors.

  6. Medline Plus. Miglitol.

  7. Centers for Disease Control and Prevention. How to treat low blood sugar (hypoglycemia).

  8. Physicians Desk Reference. Acarbose.

By Angelica Bottaro
Angelica Bottaro is a professional freelance writer with over 5 years of experience. She has been educated in both psychology and journalism, and her dual education has given her the research and writing skills needed to deliver sound and engaging content in the health space.