Acarbose: what it treats, how to take it, side effects
Last updated September 3, 2026.
Acarbose is an oral diabetes medicine that slows the digestion of carbohydrates in the gut. It blunts the blood sugar spike after meals in people with type 2 diabetes, and it can be used alone or added to other diabetes medicines.
What does it treat?
Acarbose treats type 2 diabetes as an add-on to diet and exercise. It works inside the intestine, blocking enzymes that break down starches and table sugar, so glucose enters the blood more slowly after eating. Because it acts on meals, it mainly lowers after-meal glucose rather than fasting glucose.
How do you take it?
Take acarbose three times a day with the first bite of each main meal; timing with food is what makes it work. Treatment usually starts at 25 mg three times daily, and the dose can be raised gradually to 50 mg and then 100 mg three times daily, which is the maximum approved dose. If you miss a dose, take it with your next meal or snack if one is coming soon; if it is almost time for the next dose, skip the missed one and never double up. Your doctor will track progress with blood glucose checks and periodic A1c tests.
Side effects to know
- Common: gas, diarrhea, and abdominal discomfort. In trials on doses of 50 to 300 mg three times daily, flatulence occurred in 74% of patients, diarrhea in 31%, and abdominal pain in 19%; these usually ease with time on the drug.
- Serious: dose-related rises in liver enzymes, which is why periodic liver blood tests matter, and rare reports of jaundice, hepatitis, and severe intestinal problems.
Who should not take it?
Acarbose is not for people with diabetic ketoacidosis, cirrhosis, inflammatory bowel disease, colonic ulceration, or a partial intestinal blockage, or anyone allergic to it. By itself it does not cause low blood sugar, but combined with insulin or a sulfonylurea it can, and there is a catch: because acarbose blocks table sugar from being absorbed, a low must be treated with pure glucose (glucose tablets or gel), not candy, juice, or soda. Safety in pregnancy has not been established, so insulin is generally preferred if you become pregnant.
When is it an emergency?
Call 911 for signs of a severe allergic reaction such as swelling of the face or throat or trouble breathing, and get emergency care for yellowing of the skin or eyes with dark urine, severe abdominal pain, or vomiting that will not stop. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why do I have to take acarbose with the first bite of food?
Acarbose works inside the intestine, blocking the enzymes that break down starches and sugars from the meal in front of you. Taken too early or after eating, it misses the food it is supposed to act on, so the label directs each dose with the first bite of each main meal.
Why does acarbose cause so much gas?
Undigested carbohydrate reaches the colon, where gut bacteria ferment it and produce gas. In clinical trials, 74% of patients on acarbose reported flatulence and 31% reported diarrhea, though the label notes these effects generally diminish in frequency and intensity with time.
Can acarbose cause low blood sugar?
By itself, no; even in a fasted state it does not lower glucose below normal. The risk appears when it is combined with insulin or a sulfonylurea. In that case, treat lows only with glucose tablets or gel, because acarbose blocks your body from absorbing ordinary table sugar, juice, or candy.
How long does acarbose take to work?
It acts on the meal you take it with, so after-meal glucose readings can improve within days. The full picture shows up on your A1c after about three months, which is when your doctor judges whether the dose is right.
Can I take acarbose with metformin?
Yes, it is commonly combined with metformin or other diabetes medicines when one drug alone is not enough. The combination does not add much hypoglycemia risk on its own, but your prescriber should know everything you take.
Does acarbose affect the liver?
It can raise liver enzymes in a dose-related way, and rare cases of jaundice and hepatitis have been reported. Your doctor may check liver blood tests, especially in the first year, and you should report dark urine or yellowing of the skin or eyes promptly.