Miglitol (Glyset) vs Acarbose: Price, Dosage and Side Effects Compared

Miglitol (brand name Glyset) and acarbose (Precose in the US, Glucobay elsewhere) are the two alpha-glucosidase inhibitors used for type 2 diabetes. Both slow the digestion of starch and sugar in the gut, so blood sugar rises less after meals. People usually look them up for one of three reasons: the price of Glyset, how the doses work, or whether the gas and bloating are worth it. This guide answers all three from the US labels, a Cochrane review, two large acarbose outcome trials and US pharmacy cost data.

We sell Mignar 25 (miglitol 25 mg, Glenmark) and Glucobay 50 and Glucobay 25 (acarbose, Bayer Zydus), so we have an interest in both. The evidence below favours acarbose on cost and on outcome data, and we say so.

The short answer

Both drugs lower HbA1c by less than one percentage point compared with placebo: a Cochrane review put the effect at 0.77 points for acarbose and 0.68 points for miglitol. Both are taken three times a day with the first bite of each main meal, both start at 25 mg, and both cause gas and diarrhea in many people. Neither causes low blood sugar on its own. The main differences are that miglitol is absorbed into the blood and cleared by the kidneys, while acarbose stays mostly in the gut but can raise liver enzymes and is not for people with cirrhosis. In the US both brand names are discontinued, generic acarbose is cheap (about $15 a month on pharmacy cost data), and generic miglitol was about ten times more expensive before it dropped out of the national price survey.

What alpha-glucosidase inhibitors do

Starch and table sugar have to be broken down by enzymes in the lining of the small intestine before they can be absorbed. Miglitol and acarbose block those enzymes (alpha-glucosidases), so carbohydrate is absorbed more slowly and further down the gut. The result is a smaller rise in blood sugar after meals. Neither drug makes the pancreas release more insulin, which is why neither causes hypoglycemia when used alone.

The undigested carbohydrate that reaches the large bowel is fermented by bacteria. That is where the gas, bloating and diarrhea come from, and why the labels start at a low dose and increase slowly.

Miglitol vs acarbose at a glance

Feature	Miglitol (Glyset)	Acarbose (Precose, Glucobay)
Absorbed into the blood?	Yes: 25 mg is completely absorbed and 100 mg is 50% to 70% absorbed; cleared unchanged by the kidneys	Less than 2% absorbed as active drug
Starting dose	25 mg three times a day	25 mg three times a day
Usual maintenance	50 mg three times a day	50 to 100 mg three times a day
Maximum dose	100 mg three times a day	50 mg three times a day up to 60 kg; 100 mg three times a day above 60 kg
HbA1c vs placebo (Cochrane)	0.68 points	0.77 points
Liver enzyme monitoring	Not required by the label	Every 3 months in the first year
Severe kidney disease	Not recommended (creatinine clearance under 25 mL/min or serum creatinine over 2.0 mg/dL)	Not recommended (serum creatinine over 2.0 mg/dL)
Cirrhosis	Not listed as a contraindication	Contraindicated
US brand status	Glyset discontinued	Precose discontinued

Miglitol dosage

The US miglitol label (the generic version of Glyset, which carries the same labeling) gives these steps:

• Start: 25 mg three times a day, taken with the first bite of each main meal. Some people start with 25 mg once a day and add doses as the gut adjusts.
• After 4 to 8 weeks: increase to 50 mg three times a day, the usual maintenance dose.
• After about 3 months on 50 mg: check HbA1c. If control is not good enough, the dose can go to 100 mg three times a day, the maximum.

The label notes that 200 mg three times a day lowered blood sugar further in trials but caused more gut side effects, and it is not a recommended dose. Taking the tablet long before or after the meal reduces its effect, because it has to be in the gut when the carbohydrate arrives.

Acarbose dosage

The acarbose label (generic Precose, revised August 2025) uses the same pattern with a weight limit:

• Start: 25 mg three times a day with the first bite of each main meal, or 25 mg once a day increasing to three times a day.
• Adjust every 4 to 8 weeks: 50 mg three times a day, then 100 mg three times a day if needed.
• Maximum: 50 mg three times a day for people weighing 60 kg or less, 100 mg three times a day above 60 kg.

The weight limit exists because liver enzyme rises were more common at higher doses and in lighter patients. In the label's pooled trials, doses above 50 mg three times a day did not lower HbA1c significantly more, and the Cochrane review concluded there is "no need for dosages higher than 50 mg acarbose t.i.d."

How much do they lower HbA1c?

Each label reports placebo-controlled trials. These were separate trial programmes, so the numbers below are not a head-to-head comparison.

Dose (three times a day)	Miglitol, label Study 3 (6 months)	Acarbose, label pooled studies
25 mg	0.26 points	0.44 points (n=110)
50 mg	0.40 points	0.77 points (n=131)
100 mg	0.81 points	0.74 points (n=244)

In miglitol Study 3, only the 100 mg and 200 mg doses reached statistical significance. Other miglitol studies in the label found 50 mg three times a day lowered HbA1c by 0.58 points (a one-year US study) and 0.69 points (a 14-week US study) compared with placebo. The miglitol label also gives one-hour after-meal glucose reductions in Study 3 of 35 to 64 mg/dL at the recommended doses (87 mg/dL at 200 mg, above the maximum).

For comparison, the Cochrane review found alpha-glucosidase inhibitors seemed inferior to sulfonylureas for glucose control. They are usually added to other treatment or used when other drugs are not suitable.

Gas, diarrhea and stomach pain

The gut side effects are the main reason people stop these drugs. Here are the rates in each label's US placebo-controlled trials:

Side effect	Miglitol (n=962)	Placebo (n=603)	Acarbose (n=1,255)	Placebo (n=999)
Flatulence	41.5%	12.0%	74%	29%
Diarrhea	28.7%	10.0%	31%	12%
Abdominal pain	11.7%	4.7%	19%	9%

The acarbose trials included doses up to 300 mg three times a day, three times today's maximum, while the miglitol trials used 25 to 100 mg. So the higher acarbose flatulence rate is partly a dose effect, and the tables are not directly comparable. The miglitol label says diarrhea and abdominal pain tended to ease with continued treatment.

The only direct comparison of side effects we found was small: a crossover study in 22 healthy Japanese men (Aoki 2010) found more flatus and more bloating on the first day with acarbose, and softer stools with miglitol. It did not study people with diabetes.

Other side effects in the labels

• Miglitol: skin rash in 4.3% vs 2.4% on placebo; low serum iron in 9.2% vs 4.2%, which usually did not persist and was not linked to a fall in hemoglobin. Reports after marketing include ileus (blocked bowel) and, rarely, gas cysts in the bowel wall (pneumatosis cystoides intestinalis).
• Acarbose: liver enzyme rises (see below), small falls in hematocrit, and after marketing, rare reports of fulminant hepatitis, jaundice, skin reactions, low platelets, ileus and pneumatosis cystoides intestinalis.

Acarbose and the liver

In long-term US studies of acarbose at doses up to 300 mg three times a day, liver enzymes (ALT or AST) rose above the normal range in 14% vs 7% on placebo, above three times normal in 3% vs 1%. These rises had no symptoms, reversed when the drug was stopped, were more common in women and were dose related. At doses up to 100 mg three times a day, rates were similar to placebo.

After marketing, in about 3 million patient-years, 62 cases of very high liver enzymes (over 500 IU/L) were reported, 29 with jaundice. 41 of the 62 were taking 100 mg three times a day or more, and 33 of the 45 with a known weight were under 60 kg. Fatal fulminant hepatitis has been reported, though the link to acarbose is unclear. The label asks for liver tests every 3 months in the first year and periodically after that. Miglitol's label has no equivalent warning.

Who should not take them

Both labels list these contraindications:

• diabetic ketoacidosis
• inflammatory bowel disease, colonic ulceration or partial intestinal obstruction, or a tendency to obstruction
• chronic bowel disease with marked problems of digestion or absorption, or conditions that get worse with more gas in the intestine
• allergy to the drug

Acarbose is also contraindicated in cirrhosis. The miglitol label says its pharmacokinetics are not altered in cirrhosis.

Kidneys are the other dividing line. Miglitol is cleared by the kidneys, and with a creatinine clearance under 25 mL/min its blood levels more than double; the label says lowering the dose would not correct this because miglitol acts in the gut, safety data are limited, and treatment is not recommended. Both labels also say treatment is not recommended when serum creatinine is above 2.0 mg/dL.

Low blood sugar: use glucose, not sugar

On their own, neither drug causes hypoglycemia. But many people take them with a sulfonylurea (such as glimepiride or glipizide) or insulin, and those can cause lows. If that happens, the labels say to treat it with glucose (dextrose) tablets or gel, not table sugar, juice sweetened with sucrose or sweets. These drugs block the breakdown of table sugar, so it works too slowly. Severe lows need intravenous glucose or glucagon.

If you take one of these drugs with a sulfonylurea, keep glucose tablets with you and tell family members which kind of sugar to give. Your doctor may lower the sulfonylurea or insulin dose when you start.

Drug interactions

Drug	Miglitol	Acarbose
Digoxin	Lowered digoxin levels by 19% to 28% in healthy volunteers, but not in diabetic patients in a 14-day study	May lower digoxin levels; the digoxin dose may need adjusting
Ranitidine	Bioavailability reduced by 60%	No effect
Propranolol	Bioavailability reduced by 40%	No effect
Charcoal, digestive enzymes (amylase, pancreatin)	May reduce effect; do not take together	May reduce effect; do not take together
Metformin	Metformin levels 12% to 13% lower, not significant	Metformin peak about 20% lower, total exposure unchanged

Acarbose also interferes with the 1,5-anhydroglucitol (GlycoMark) blood test, so that test should not be used to judge control while taking it.

Glyset price and cost in the US

Neither brand is sold in the US any more. The FDA's approvals database lists Glyset (Pfizer, application NDA 020682) and Precose (Bayer, NDA 020482) as discontinued, and the FDA has determined that Precose was not withdrawn for safety or effectiveness reasons. The only miglitol application still marked as a prescription product is a generic from Orient Pharma. Several acarbose generics remain listed.

The best public measure of US pharmacy cost is the National Average Drug Acquisition Cost (NADAC), what pharmacies pay to buy the drug, not what you pay at the counter. Using the latest week each product was priced, for 90 tablets (one tablet three times a day for 30 days):

Product	NADAC per tablet	Week	90 tablets
Acarbose 25 mg	$0.17982	14 Oct 2026	$16.18
Acarbose 50 mg	$0.16905	14 Oct 2026	$15.21
Acarbose 100 mg	$0.27398	14 Oct 2026	$24.66
Miglitol 25 mg	$1.75452	13 May 2026	$157.91
Miglitol 50 mg	$1.76405	11 Feb 2026	$158.76
Miglitol 100 mg	$2.03118	13 Aug 2025	$182.81

At the usual 50 mg dose, miglitol cost pharmacies about 10.4 times as much per tablet as acarbose. Only one miglitol product was priced, and each strength has since dropped out of the survey, which suggests US supply is thin. If your pharmacy cannot get miglitol, ask your doctor whether acarbose or another drug class would suit you.

Availability outside the US

• UK: NHS records list Glucobay 50 mg as discontinued; generic acarbose is listed in the NHS Drug Tariff. We could not confirm a UK miglitol product.
• Canada: Bayer's Glucobay registration was cancelled in July 2023, while generic acarbose from Marcan is listed as marketed. We found no Glyset listing in Health Canada's drug database.
• Australia: generic acarbose 50 mg and 100 mg are listed on the Pharmaceutical Benefits Scheme.
• Ireland: Sanofi's miglitol brand, Diastabol, was withdrawn in 2011.
• India: miglitol is sold as Mignar (Glenmark) and acarbose as Glucobay (Bayer Zydus), among other brands.

Does acarbose prevent diabetes or heart disease?

Acarbose has outcome data that miglitol does not. Two large trials tested it in people with impaired glucose tolerance (blood sugar above normal but below the diabetes threshold):

• STOP-NIDDM (2002): 1,429 people took acarbose 100 mg three times a day or placebo. Diabetes developed in 32% vs 42% (hazard ratio 0.75). But 31% stopped acarbose early, compared with 19% on placebo; flatulence and diarrhoea were the most common side effects.
• ACE (2017): 6,522 Chinese patients with coronary heart disease took acarbose 50 mg three times a day or placebo for a median of 5 years. The main combined outcome (cardiovascular death, heart attack, stroke, or hospital admission for unstable angina or heart failure) was not reduced (14% vs 15%, hazard ratio 0.98), and neither was the narrower combination of cardiovascular death, heart attack and stroke. New diabetes was less common (13% vs 16%).

The Cochrane review found no evidence that alpha-glucosidase inhibitors reduce death or illness in people with type 2 diabetes. No outcome trial of miglitol exists.

Weight

Neither drug is known to cause weight gain, and both labels say they reduce the weight gain seen with sulfonylureas, which is a difference from sulfonylureas and insulin. The Cochrane review found acarbose lowered BMI by a small 0.17 kg/m2. A small open-label Japanese study of 81 overweight patients (Sugihara 2014) found body weight and BMI fell significantly in the miglitol group over 12 weeks, but the trial was small and not blinded.

Which one should you choose?

On the evidence, acarbose has more going for it: larger trial programmes, two long outcome trials, wide availability and a far lower price. Its drawbacks are the liver enzyme monitoring, the contraindication in cirrhosis and, at high doses, more gas.

Miglitol may suit someone who cannot take acarbose because of liver disease, or who could not tolerate acarbose's side effects, provided their kidneys work well. It also has more drug interactions (ranitidine, propranolol). The choice belongs with your doctor, who will weigh your kidney and liver function, other medicines and what else has been tried.

Where they fit in type 2 diabetes treatment

Metformin is the usual first medicine for type 2 diabetes. Newer classes such as SGLT2 inhibitors and GLP-1 medicines have heart and kidney outcome data that alpha-glucosidase inhibitors lack. Alpha-glucosidase inhibitors are mostly used as add-ons, in people with high after-meal glucose, or where other drugs are unsuitable or unaffordable. In the acarbose label, adding acarbose (50 to 100 mg three times a day; up to 300 mg in the sulfonylurea study) lowered HbA1c by 0.65 points on top of metformin, 0.54 points on top of a sulfonylurea and 0.69 points on top of insulin.

See our guides to metformin vs glimepiride, Januvia vs Tradjenta and Jardiance vs Farxiga for how other classes compare.

Tips for taking them

• Take each dose with the first bite of a main meal; the drug needs to be in the gut when the food arrives.
• Start low and increase slowly, as the labels describe; it gives the gut time to adjust.
• Carry glucose tablets if you also take a sulfonylurea or insulin.
• Do not take digestive enzyme supplements or charcoal at the same time.

When to see a doctor

Get medical help for severe abdominal pain, a swollen abdomen with vomiting or no bowel movements (possible blockage), yellow skin or eyes, dark urine, or a rash. Tell your doctor if diarrhea is severe or does not settle, if your blood sugar stays high after three months on the maintenance dose, or before starting any new medicine.

Related guides

• Metformin dosage guide
• Amaryl (glimepiride): dosing and hypoglycaemia risk
• Onglyza (saxagliptin) guide
• Type 2 diabetes treatments

Sources

• Miglitol tablets, US prescribing information, Orient Pharma Co., Ltd. (generic of Glyset), revised December 2014. DailyMed
• Acarbose tablets, US prescribing information, Strides Pharma (generic of Precose), revised August 2025. DailyMed
• US Food and Drug Administration, Drugs@FDA via openFDA: GLYSET NDA 020682 and PRECOSE NDA 020482, searched 15 October 2026.
• Centers for Medicare and Medicaid Services. National Average Drug Acquisition Cost (NADAC), weekly data, retrieved 15 October 2026. data.medicaid.gov
• van de Laar FA et al. Alpha-glucosidase inhibitors for patients with type 2 diabetes: results from a Cochrane systematic review and meta-analysis. Diabetes Care 2005;28(1):154-63. PMID 15616251.
• Aoki K et al. Comparison of adverse gastrointestinal effects of acarbose and miglitol in healthy men: a crossover study. Internal Medicine 2010;49(12):1085-7. PMID 20558922.
• Sugihara H et al. Comparison of three alpha-glucosidase inhibitors for glycemic control and bodyweight reduction in Japanese patients with obese type 2 diabetes. Journal of Diabetes Investigation 2014;5(2):206-12. PMID 24843762.
• Chiasson JL et al. Acarbose for prevention of type 2 diabetes mellitus: the STOP-NIDDM randomised trial. Lancet 2002;359(9323):2072-7. PMID 12086760.
• Holman RR et al. Effects of acarbose on cardiovascular and diabetes outcomes in patients with coronary heart disease and impaired glucose tolerance (ACE). Lancet Diabetes and Endocrinology 2017;5(11):877-886. PMID 28917545.
• NHS Dictionary of Medicines and Devices: Glucobay 50 mg tablets. NHSBSA; generic acarbose 50 mg Drug Tariff listing via OpenPrescribing
• Pharmaceutical Benefits Scheme, acarbose items 8188Y and 8189B. PBS
• Health Products Regulatory Authority (Ireland), Diastabol 50 mg, licence PA0540/144/001, withdrawn 11 April 2011.
• Health Canada Drug Product Database, searched October 2026. Health Canada

This guide is for information only and is not medical advice. Miglitol and acarbose are prescription medicines. Do not start, stop or change a diabetes medicine without your doctor's advice.