What is the major drawback of using acarbose in most patients?

October 10, 2025 •

4 min read

In clinical trials, up to 74% of patients using acarbose reported experiencing excessive gas. The major drawback of using acarbose in most patients is the significant gastrointestinal side effects, including flatulence, bloating, and diarrhea, which stem directly from its mechanism of action.

Quick Summary

Acarbose's primary drawback is the common occurrence of gastrointestinal side effects, such as gas, bloating, and diarrhea, caused by undigested carbohydrates fermenting in the gut. These effects often lead to poor patient tolerability.

Key Points

Prevalent Gastrointestinal Side Effects: The most common and bothersome drawback of acarbose is its high rate of GI side effects, such as flatulence, bloating, and diarrhea.
Mechanism of Action-Related: These GI issues are a direct consequence of acarbose's function, which delays carbohydrate breakdown, leading to bacterial fermentation in the colon.
Impact on Adherence: The significant discomfort caused by these side effects can lead to poor patient tolerability and discontinuation of the medication.
Management Strategies Exist: Side effects can often be managed by starting with a low dose, gradual titration, and dietary adjustments, though this requires careful patient education.
Less Commonly Prescribed: Due to its side effect profile and the availability of newer, often better-tolerated agents, acarbose is not as widely used as other diabetes medications.
Inconvenient Dosing: Acarbose must be taken with the first bite of each main meal, making the three-times-daily dosing schedule less convenient than once-daily alternatives.
Hypoglycemia Treatment Difference: While hypoglycemia risk is low when used alone, acarbose interferes with the breakdown of table sugar, so pure glucose (not sucrose) is needed to treat low blood sugar episodes.

Understanding the Mechanism: Why Acarbose Causes Gastrointestinal Distress

Acarbose is an alpha-glucosidase inhibitor, a class of oral medications used to manage type 2 diabetes. Its purpose is to slow the absorption of carbohydrates from the diet, thereby preventing the sharp spike in blood glucose levels that often occurs after a meal. It accomplishes this by blocking the enzymes in the small intestine that break down complex carbohydrates into simple sugars.

While this mechanism is effective at lowering postprandial (after-meal) blood sugar, it also leads to the drug's most significant drawback: frequent and bothersome gastrointestinal (GI) side effects. When these undigested complex carbohydrates continue their journey to the large intestine, they are fermented by gut bacteria. This bacterial fermentation is what produces the excessive gas, bloating, and other digestive discomfort.

The Most Common Gastrointestinal Side Effects

The GI side effects are the most commonly reported adverse events and can significantly impact a patient's quality of life and adherence to treatment. The frequency of these effects can vary, but studies show they are quite prevalent.

Flatulence: Excessive gas is the most frequent complaint, affecting a high percentage of patients, particularly when starting therapy or on higher doses.
Diarrhea: Many patients also report loose stools or diarrhea, which can range from mild to more severe.
Abdominal Pain and Bloating: Discomfort, cramping, and a bloated feeling in the abdomen are also common as a result of increased gas production.

These symptoms are often dose-related and are most prominent at the start of treatment. For many patients, the severity of these symptoms decreases over time as their body adjusts. However, some patients find the side effects intolerable, leading them to discontinue the medication.

Strategies for Managing Acarbose's Side Effects

Because the GI side effects are a direct consequence of the drug's action, management often involves mitigating the factors that exacerbate them. By working closely with a healthcare provider, patients can often reduce their discomfort and continue with the therapy.

Start Low and Go Slow: The most effective strategy is to begin with a low dose and gradually increase it. This allows the patient's gut to adapt to the changes in carbohydrate digestion, often reducing the severity of symptoms over several weeks.
Dietary Adjustments: Reducing the amount of simple sugars and starches in the diet can lessen the load on the intestines and decrease fermentation. A diet high in complex carbohydrates is recommended, but managing portion sizes is key to minimizing GI distress.
Proper Timing with Meals: Acarbose must be taken with the first bite of each main meal to be effective. Missing a dose or taking it too late will diminish its postprandial glucose-lowering effect.
Distinguishing Symptoms: It's important for patients to know that if they experience hypoglycemia (low blood sugar) while also on other diabetes medications (like insulin or sulfonylureas), they must use pure glucose tablets or gel for treatment, not sucrose (table sugar). Acarbose inhibits the breakdown of sucrose, making it ineffective for rapidly correcting low blood sugar.

Acarbose vs. Other Diabetes Medications: A Comparison

To put the drawback of acarbose into perspective, it's helpful to compare its side effect profile with other common oral diabetes medications. The comparison highlights why GI tolerability remains a major factor in prescribing decisions.


Feature	Acarbose	Metformin	SGLT2 Inhibitors (e.g., canagliflozin)	DPP-4 Inhibitors (e.g., sitagliptin)
Primary Mechanism	Blocks carbohydrate breakdown in the gut	Decreases glucose production by the liver and improves insulin sensitivity	Blocks glucose reabsorption in the kidneys, leading to excretion in urine	Increases incretin hormones to boost insulin and reduce glucagon
Major Side Effects	Flatulence, bloating, diarrhea, abdominal pain	Diarrhea, stomach upset, nausea	Genitourinary infections, increased urination	Generally well-tolerated, rare allergic reactions
Onset of Action	Immediate effect on postprandial glucose	Gradual effect over several weeks	Gradual effect	Rapid effect
Hypoglycemia Risk	Minimal when used alone, increases when combined with insulin or sulfonylureas	Low risk	Low risk	Minimal risk
Weight Effect	Weight-neutral or slight weight loss	Often causes slight weight loss	Causes weight loss	Weight-neutral
Dosing Schedule	Taken with the first bite of each meal, typically three times daily	Typically twice daily with meals	Once daily	Once daily

Other Considerations and Rare Side Effects

While GI side effects are the most common drawback, other factors also influence the choice of acarbose. The required three-times-daily dosing schedule can be inconvenient for some patients, potentially impacting adherence. In comparison, many newer diabetes drugs offer once-daily dosing. Additionally, acarbose's glucose-lowering efficacy, particularly on HbA1c, is considered more modest than other therapies when used as monotherapy.

Rare but serious side effects associated with acarbose use include elevated liver enzymes and, even more rarely, pneumatosis cystoides intestinalis (gas cysts in the intestinal wall). Contraindications include patients with inflammatory bowel disease, liver cirrhosis, or intestinal obstruction. These factors, combined with the prevalent GI issues, contribute to acarbose being a less commonly prescribed option compared to newer alternatives.

Conclusion: The Trade-off of Acarbose Therapy

In conclusion, the major drawback of using acarbose is its propensity for causing significant gastrointestinal side effects, most notably flatulence, bloating, and diarrhea, in a large proportion of patients. This issue is a direct result of its non-systemic mechanism of action, which causes undigested carbohydrates to be fermented in the colon. While these symptoms often lessen over time with careful dose titration and dietary management, they represent a significant barrier to treatment adherence for many. This, combined with a demanding dosing schedule and more modest overall efficacy compared to some alternatives, positions acarbose as a less preferred option for many individuals with type 2 diabetes. The decision to use acarbose requires a careful consideration of its benefits in controlling postprandial glucose against the potential for significant GI discomfort and other practical factors.

For more information on medications for type 2 diabetes, you can refer to the MedlinePlus Drug Information.

Frequently Asked Questions

Acarbose inhibits enzymes that break down carbohydrates in the small intestine. These undigested carbohydrates then travel to the colon, where they are fermented by bacteria, producing gas, bloating, and discomfort.

Yes, for many patients, the gastrointestinal side effects tend to decrease in severity over the first few weeks of therapy as the body adjusts to the medication.

Starting with a low dose and increasing it gradually, as well as following a diet that is lower in simple sugars, can help minimize the side effects.

For maximum effectiveness and to minimize side effects, it is crucial to take acarbose with the first bite of each main meal.

Diarrhea is a common side effect of acarbose. While often mild to moderate, in some cases it can be significant. If it is severe or persistent, a healthcare provider should be consulted.

Acarbose inhibits the enzymes that break down sucrose (table sugar) into absorbable glucose. Therefore, pure glucose (dextrose) tablets or gel must be used to treat hypoglycemia effectively.

While it is an older and effective medication, acarbose is less commonly prescribed now due to its gastrointestinal side effects and the availability of newer, often better-tolerated, diabetes drugs.

Acarbose is contraindicated for patients with inflammatory bowel disease, liver cirrhosis, intestinal obstruction, or other chronic intestinal diseases that could be worsened by increased gas formation.