Acarbose Side Effects: What to Expect and When to Call Your Doctor

Acarbose works inside your gut, and that's where most of its side effects show up. The good news: most are temporary, manageable, and not dangerous. The less-good news: for some patients, the GI effects are significant enough to affect quality of life. Here's a complete, honest picture of acarbose side effects — what to expect, how to manage them, and when to call your doctor.

The Most Common Side Effects of Acarbose

In U.S. placebo-controlled clinical trials, the three most commonly reported side effects of acarbose at doses of 50–300 mg three times daily were:

Flatulence (gas): 74% — compared to 29% in patients taking placebo

Diarrhea: 31% — compared to 12% in placebo patients

Abdominal pain: 19% — compared to 9% in placebo patients

These side effects are caused by the mechanism of acarbose itself. When carbohydrates aren't broken down and absorbed in the small intestine (as normal), they pass to the large intestine where bacteria ferment them — producing gas. These symptoms tend to be worst in the first few weeks of treatment and usually improve as your gut adapts.

How to Reduce GI Side Effects

The most important strategy for reducing GI side effects is slow titration. Acarbose is typically started at 25 mg three times daily, then increased every 4–8 weeks based on tolerability and blood sugar response. Starting too high or increasing too quickly is the number one reason patients experience severe GI effects.

Other strategies:

Take acarbose with the very first bite of each meal — not before, not after. This timing is critical for both efficacy and tolerability.

Follow a low-carbohydrate meal if GI symptoms are severe — less carbohydrate to ferment means less gas

Avoid digestive enzyme supplements (amylase, pancreatin) — they break down acarbose and reduce its effectiveness

Stay consistent — many patients find GI symptoms diminish significantly after 4–8 weeks of consistent use

Does Acarbose Cause Low Blood Sugar (Hypoglycemia)?

Acarbose does not cause hypoglycemia when used alone. Unlike sulfonylureas or insulin, acarbose doesn't stimulate insulin release — it simply slows carbohydrate digestion. However, if you take acarbose combined with insulin or a sulfonylurea, the combined effect on blood sugar can cause hypoglycemia.

Critical point about treating hypoglycemia on acarbose: If you develop low blood sugar while taking acarbose, you must use dextrose (glucose), NOT table sugar or sucrose. Acarbose blocks the enzyme that breaks down sucrose into absorbable glucose, so cane sugar may not raise your blood sugar quickly enough in an emergency. Use glucose tablets, glucose gel, honey, raisins, or fruit juice.

Serious Side Effects to Watch For

Rare but serious side effects include:

Elevated liver enzymes. In rare cases, acarbose can cause liver enzyme elevations (transaminase increases above 500 IU/L have been reported). Your doctor should check liver function every 3 months during the first year of therapy. Signs of liver problems include jaundice (yellow skin or eyes), dark urine, upper right stomach pain, or unusual fatigue.

Fulminant hepatitis. Very rare cases of severe liver failure have been reported. The relationship to acarbose is uncertain in most cases, but it's a reason why liver monitoring is recommended.

Pneumatosis cystoides intestinalis. A very rare condition where gas-filled cysts form in the intestinal wall. Symptoms include diarrhea, mucus discharge, rectal bleeding, and constipation. If you develop these symptoms, stop acarbose and seek medical attention immediately.

Allergic skin reaction. Rare reports of rash, redness, and swelling. Seek immediate medical attention if you develop hives, difficulty breathing, or swelling of the face.

When to Call Your Doctor

Contact your provider if:

GI side effects are severe and not improving after 4–6 weeks

You notice yellow skin or eyes, dark urine, or upper right belly pain

You experience rectal bleeding, mucus in stool, or unusual constipation

You have signs of low blood sugar (shakiness, confusion, sweating, fast heartbeat) — especially if you're also on insulin or a sulfonylurea

You develop any allergic reaction (hives, rash, swelling, difficulty breathing)

Does Acarbose Cause Weight Gain?

No. Acarbose is weight-neutral or may contribute to mild weight loss. Unlike sulfonylureas or insulin, it does not stimulate insulin secretion and does not promote fat storage. Some post-marketing data has suggested a modest average weight reduction in patients taking acarbose long-term.

Also see: Acarbose Drug Interactions: What to Avoid and What to Tell Your Doctor