November 28, 2023

What Is Glyset?

Glyset (miglitol) is an oral prescription drug used with diet and exercise to improve blood sugar control in adults with type 2 diabetes.

Glyset is in a drug class called alpha-glucosidase inhibitors. It works by slowing the breakdown and absorption of sugar in the small intestine, which helps reduce blood sugar after meals.

Glyset is available as a tablet that is taken by mouth.

Drug Facts

Generic Name: Miglitol

Brand Name(s): Glyset

Drug Availability: Prescription

Administration Route: Oral

Therapeutic Classification: Alpha-glucosidase inhibitor

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Miglitol

Dosage Form(s): Tablet

What Is Glyset Used For?

The Food and Drug Administration (FDA) approved Glyset to be used with diet and exercise to improve blood sugar control in adults with type 2 diabetes.

Controlling blood sugar can help prevent complications of diabetes, such as kidney, eye, and nerve problems, loss of limbs, and problems with sexual function. It can also help reduce the risk of a heart attack or stroke.

How to Take Glyset

Before taking Glyset, read the label and information leaflet that comes with your prescription. Consult your healthcare provider if you have any questions.

Use Glyset exactly as directed by your healthcare provider, and do not skip doses. Glyset is usually taken three times daily (at the beginning of each main meal).

Check blood sugar as directed by your healthcare provider. If Glyset is your only diabetes medication, you should not experience low blood sugar. However, if taking it with other diabetes drugs or insulin, talk to your healthcare provider about how to spot and treat hypoglycemia (low blood sugar). Ask them whether a prescription for glucagon, which can be used in an emergency low blood sugar situation, is right for you.


Store Glyset at room temperature (between 68 F and 77 F), away from heat, direct light, and moisture. Do not store it in the bathroom. Keep this medication in its original labeled container and out of reach of children and pets. Keep the bottle tightly closed when not in use.

How Long Does Glyset Take to Work?

Glyset starts working quickly. Measuring your blood sugar one to two hours after eating will give you an idea of how the medication works to lower your blood sugar. This can help your healthcare provider make dosage adjustments if necessary (after several weeks of treatment). Your healthcare provider will also measure your hemoglobin A1C, which shows blood sugar control over three months.

What Are the Side Effects of Glyset?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at or 1-800-FDA-1088.

Like other medications, Glyset can cause side effects. Tell your healthcare provider about any side effects you experience while taking this medication.

Common Side Effects

The most common side effects of Glyset are:

  • Diarrhea
  • Gas
  • Stomach pain
  • Rash

Severe Side Effects

Call your healthcare provider immediately if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Hypersensitivity reaction or anaphylaxis: Symptoms of an allergic reaction can include rash, hives, swelling around the lips, tongue, and face, and difficulty breathing.
  • Ileus: A condition where the bowel does not work properly. Symptoms may include bloating, vomiting, constipation, cramps, and appetite loss.
  • Pneumatosis cystoides intestinalis: In rare cases, gas-filled cysts may develop in the intestinal wall. Symptoms may include diarrhea, mucus discharge, rectal bleeding, and constipation.

Long-Term Side Effects

While many people tolerate Glyset well, long-term or delayed side effects are possible. Some long-term side effects are considered mild, such as weight loss, or moderate, such as constipation and anemia (low number of red blood cells).

Severe long-term side effects may include:

  • Pneumatosis cystoides intestinalis
  • Intussusception: A medical emergency that can cause death if not treated. In this condition, part of the intestine folds onto itself. Symptoms include vomiting, diarrhea, and stool mixed with blood and mucus.
  • Ileus
  • Stomach bleeding

Report Side Effects

Glyset may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA’s MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Glyset Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (tablets):

    • For type 2 diabetes:

      • Adults—At first the dose is 25 milligrams (mg) three times a day, at the start (with the first bite) of each main meal. After four to eight weeks, your doctor may increase your dose to 50 mg three times a day. Then, after an additional twelve weeks, if necessary, your doctor may increase your dose to 100 mg three times a day.
      • Children—Use and dose must be determined by your doctor.


People with liver problems can take Glyset. However, those with kidney problems may need to use Glyset cautiously or avoid it altogether, depending on the degree of impairment. People with a creatinine clearance of less than 25 milliliters (mL) per minute should not take Glyset.

Peoople who are pregnant, planning to become pregnant, or breastfeeding should consult their healthcare provider regarding Glyset use. Glyset is not considered a first-line agent in diabetes during pregnancy. It can also be present in breast milk, so breastfeeding is not recommended during its use.

Missed Dose

If you miss a dose, take it as soon as you remember, as long as you can take it with a meal. Glyset should only be taken with a meal.

If it is almost time for the next dose, skip the missed dose and resume with the next dose. Do not double up on doses to try to make up for a missed dose.

Overdose: What Happens If I Take Too Much Glyset?

Taking too much Glyset can cause temporary increases in stomach problems such as gas, diarrhea, and discomfort. It is not expected to cause low blood sugar when taken alone.

What Happens If I Overdose on Glyset?

If you think you or someone else may have overdosed on Glyset, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn’t breathing after taking Glyset, call 911 immediately.


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Your doctor will want to check your progress at regular visits, especially during the first few weeks that you take this medicine.

It is very important to follow carefully any instructions from your health care team about:

  • Alcohol—Drinking alcohol may cause severe low blood sugar. Discuss this with your health care team.
  • Other medicines—Do not take other medicines during the time you are taking miglitol unless they have been discussed with your doctor. This especially includes nonprescription medicines such as aspirin, and medicines for appetite control, asthma, colds, cough, hay fever, or sinus problems.
  • Counseling—Other family members need to learn how to prevent side effects or help with side effects if they occur. Also, patients with diabetes may need special counseling about diabetes medicine dosing changes that might occur because of lifestyle changes, such as changes in exercise and diet. Furthermore, counseling on contraception and pregnancy may be needed because of the problems that can occur in patients with diabetes during pregnancy.
  • Travel—Keep a recent prescription and your medical history with you. Be prepared for an emergency as you would normally. Make allowances for changing time zones and keep your meal times as close as possible to your usual meal times.

In case of emergency—There may be a time when you need emergency help for a problem caused by your diabetes. You need to be prepared for these emergencies. It is a good idea to wear a medical identification (ID) bracelet or neck chain at all times. Also, carry an ID card in your wallet or purse that says that you have diabetes and a list of all your medicines.

Symptoms of hypoglycemia (low blood sugar) include anxiety; behavior change similar to being drunk; blurred vision; cold sweats; confusion; cool, pale skin; difficulty in thinking; drowsiness; excessive hunger; fast heartbeat; headache (continuing); nausea; nervousness; nightmares; restless sleep; shakiness; slurred speech; or unusual tiredness or weakness.

Miglitol does not cause low blood sugar. However, it can occur if you delay or miss a meal or snack, drink alcohol, exercise more than usual, cannot eat because of nausea or vomiting, or take miglitol with another type of diabetes medicine. Symptoms of low blood sugar must be treated before they lead to unconsciousness (passing out). Different people feel different symptoms of low blood sugar. It is important that you learn which symptoms of low blood sugar you usually have so that you can treat it quickly.

If symptoms of low blood sugar occur, eat glucose tablets or gel or honey, or drink fruit juice to relieve the symptoms. Table sugar (sucrose) or regular (nondiet) soft drinks will not work. Also, check your blood for low blood sugar. Glucagon is used in emergency situations when severe symptoms such as seizures (convulsions) or unconsciousness occur. Have a glucagon kit available, along with a syringe or needle, and know how to use it. Members of your household also should know how to use it.

Symptoms of hyperglycemia (high blood sugar) include blurred vision; drowsiness; dry mouth; flushed, dry skin; fruit-like breath odor; increased urination; ketones in urine; loss of appetite; stomachache, nausea, or vomiting; tiredness; troubled breathing (rapid and deep); unconsciousness; or unusual thirst.

High blood sugar may occur if you do not exercise as much as usual, have a fever or infection, do not take enough or skip a dose of your diabetes medicine, or overeat or do not follow your meal plan.

If symptoms of high blood sugar occur, check your blood sugar level and then call your health care professional for instructions.

What Are Reasons I Shouldn’t Take Glyset?

Glyset is not appropriate for everyone. You should not take this medication if you are allergic to miglitol or any of the inactive ingredients in it. 

You should also not take Glyset if you have:

What Other Medications May Interact With Glyset?

Tell your healthcare provider about all of the medicines you take, including prescription and over-the-counter (OTC) medicines and vitamins or herbal supplements. Glyset can interact with certain medications, such as:

  • Beta-blockers such as Toprol XL (metoprolol succinate extended-release) or Tenormin (atenolol) may mask certain symptoms of low blood sugar (shaking and fast heart rate). If a beta-blocker is taken with Glyset, blood sugar will be monitored more frequently.
  • Hormonal birth control/hormone replacement: These medications may decrease the effectiveness of Glyset.
  • Lanoxin (digoxin): Glyset may decrease the effectiveness of digoxin, requiring an increased dose of digoxin if the drugs are taken together.
  • Acarbose: This combination can cause low blood sugar and should be avoided (both acarbose and miglitol are in the same drug class). However, insulin or other medications used for diabetes can also increase the risk for low blood sugar when combined with Glyset and may require a dosage adjustment.
  • Synthroid (levothyroxine): This thyroid medication can decrease how well Glyset works.

Other drug interactions may occur. Consult your healthcare provider for a complete list.

What Medications Are Similar?

Besides Glyset, the only other alpha-glucosidase inhibitor is called acarbose. In studies, miglitol worked just as well as acarbose but at lower doses.

There are also various oral medications available to help control blood sugar in adults with type 2 diabetes, including:

  • Dipeptidyl peptidase-4 (DPP-4) inhibitors: Januvia (sitagliptin), Nesina (alogliptin), Onglyza (saxagliptin), Tradjenta (linagliptin)
  • Glinides: Repaglinide, nateglinide
  • Glumetza, Fortamet (metformin)
  • Sodium-glucose cotransporter-2 (SGLT2) inhibitors: Invokana (canagliflozin), Farxiga (dapagliflozin), Jardiance (empagliflozin)
  • Sulfonylureas: Amaryl (glimepiride), Glucotrol (glipizide), Micronase, Diabeta, and Glynase (glyburide)
  • Thiazolidinedione: Actos (pioglitazone)

A drug class that is becoming popular for type 2 diabetes is a category known as glucagon-like peptide 1 (GLP-1) receptor agonists. These drugs are not insulin. They help the pancreas release insulin, help prevent the liver from making too much sugar, and slow down food leaving the stomach. 

GLP-1 receptor agonists include the oral drug Rybelsus (semaglutide) and the following injectable drugs: 

People with type 2 diabetes may also need injectable insulin to improve blood sugar control. There are several types of short-acting (e.g., Humalog and Novolog) and long-acting (e.g., Lantus and Levemir) insulin.

This is a list of drugs also prescribed for type 2 diabetes. It is NOT a list of drugs recommended to take with Glyset. Talk to your pharmacist or a healthcare provider if you have questions.

Frequently Asked Questions

  • What is Glyset used for?

    Glyset is used with diet and exercise to improve blood sugar control in adults with type 2 diabetes. Keeping your blood sugar under control is especially important for preventing diabetes complications and reducing your risk of heart disease.

  • How does Glyset work?

    Glyset works by slowing the breakdown and absorption of sugar in the small intestine. This helps lower blood sugar after meals.

  • What drugs should not be taken with Glyset?

    Glyset should not be taken with acarbose, another alpha-glucosidase inhibitor, due to the risk of low blood sugar and additive side effects.

    Insulin or other drugs that lower blood sugar are sometimes used with Glyset but should be used cautiously (and may require lower doses) to reduce the risk of low blood sugar. Other drugs may interact with Glyset as well. Before taking Glyset, tell your healthcare provider about all of the medications you take, including prescription and OTC drugs, vitamins, and supplements.

  • How long does it take for Glyset to work?

    Glyset starts working quickly. Your healthcare provider will tell you how often to check your blood sugar and report back to them to determine if dosage adjustments are needed. The hemoglobin A1C level can be measured every three months and is a measure of blood sugar control.

  • What are the side effects of Glyset?

    The most common side effects are diarrhea, gas, stomach pain, and rash. Before taking Glyset, talk to your healthcare provider about what side effects to expect and what to do if you experience them.

  • How do I stop taking Glyset?

    Your healthcare provider will advise you on how long to take Glyset. Do not stop taking Glyset without guidance from your healthcare provider.

How Can I Stay Healthy While Taking Glyset?

Before taking Glyset, discuss your medical history and all medications you take with your healthcare provider. When taking Glyset, follow your healthcare provider’s instructions for use. Read the patient information leaflet that comes with your prescription and discuss any questions with your healthcare provider.

Prepare a diabetes kit with supplies to take with you everywhere you go. You may want to include:

  • A blood glucose testing meter and extra supplies (test strips, lancing device, lancets, alcohol wipes, extra batteries)
  • Emergency contact information
  • A list of current medications (including prescription, OTC, vitamins, and supplements)
  • Glucagon (injection or nasal Baqsimi) if instructed by your healthcare provider
  • Low blood sugar treatments such as glucose tablets or Smarties and small juice boxes (ask your healthcare provider if these are necessary, depending on whether you take other diabetes medications with Glyset)

Purchase and wear a medical alert bracelet or necklace at all times to alert responders that you have type 2 diabetes in the event of an emergency.

Glyset should be used in combination with diet and exercise. Talk to your healthcare provider about what kind of diet and exercise regimen to follow. A registered dietician can also be a great resource to help with eating habits and exercise changes. Monitor blood sugar as directed by your healthcare provider.

Medical Disclaimer

Verywell Health’s drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.


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