Sulfonylureas: Uses, Side Effects & How They Work
Updated: 6 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026 · How we review
Quick Answer: What are sulfonylureas?
Sulfonylureas are oral medicines for type 2 diabetes that trigger the pancreas to release more insulin, which lowers blood sugar. Common examples are glimepiride, glipizide, glyburide and gliclazide, taken once or twice a day. The main risk is low blood sugar (hypoglycemia), and they do not treat type 1 diabetes. [1]
What the research says
Sulfonylureas did not raise the risk of death, heart attack or stroke in long-term trials. A pooled analysis of 47 randomized trials with 37,650 adults with type 2 diabetes found no increase in deaths from any cause (odds ratio 1.12; 95% CI 0.96–1.30), heart-related deaths, heart attacks or strokes. (Varvaki Rados et al., PLoS Medicine, 2016) [2]
Glimepiride matched a newer diabetes pill on heart safety — but caused far more lows. In a 6,033-person trial followed for a median of 6.3 years, major heart events occurred in 12.0% of people on glimepiride and 11.8% on linagliptin. At least one low blood sugar episode happened in 37.7% on glimepiride versus 10.6% on linagliptin. (Rosenstock et al., JAMA, 2019) [3]
Keeping metformin when adding a sulfonylurea looked safer than switching. Among 77,138 people who started metformin, those who added or switched to a sulfonylurea had higher risks of severe low blood sugar (hazard ratio 7.60) and heart attack (hazard ratio 1.26) than those who stayed on metformin alone. Switching carried a higher heart attack risk than adding. (Douros et al., BMJ, 2018) [4]
Key takeaways
Sulfonylureas lower blood sugar by helping your pancreas release insulin.
They are tablets taken once or twice a day, in doses from 1 to 10 mg.
Low blood sugar is the main risk — learn the warning signs.
Never double up on a missed dose.
Keep checking your blood sugar so you and your doctor know the medicine is still working.
What are sulfonylureas?
Sulfonylureas are a group (class) of oral medicines used to treat type 2 diabetes by lowering your blood sugar (glucose). They are a long-used, low-cost option that works quickly and is easy to take. [1]
They are not used for type 1 diabetes, because in type 1 the pancreas can no longer make insulin on its own.
Your doctor chooses a specific sulfonylurea based on your health history. It's worth talking through the pros and cons together to find what fits you best.
New to diabetes? Start with our complete guide to diabetes symptoms, types and treatment.
How do sulfonylureas work?
Sulfonylureas work by attaching to the insulin-making beta cells of the pancreas and signaling them to release more insulin, which brings blood sugar down. In type 2 diabetes, your body doesn't use or release enough insulin, the hormone that keeps blood sugar in a healthy range. [1]
It happens in three steps:
They target the pancreas. The medicine attaches to specific receptors on the beta cells — the insulin-making cells of the pancreas.
Beta cells release insulin. This signal causes the cells to push more insulin into your bloodstream.
Blood sugar drops. The extra insulin helps move sugar out of the blood, bringing levels down.
Because they push insulin out no matter what your blood sugar level is, sulfonylureas can sometimes lower it too far. That is why checking your sugar matters so much.
What are the common sulfonylureas?
The most prescribed sulfonylureas are gliclazide, glimepiride, glipizide and glyburide. [1]
Generic name | Common brand names | Notes |
Gliclazide | Diamicron, Diamicron MR | Not approved in the U.S. |
Glimepiride | Amaryl | Widely available |
Glipizide | Glucotrol XL | Widely available |
Glyburide | DiaBeta, Glynase | Widely available |
[1]
Glimepiride is also sold combined with another diabetes drug in one tablet — see our guide to pioglitazone and glimepiride.
What are the benefits and risks of sulfonylureas?
The benefits of sulfonylureas are proven, fast blood sugar lowering at a low cost, while the main risk is low blood sugar, along with weight gain, nausea or diarrhea, and rarely a skin rash. [1]
Benefits | Risks and side effects |
Proven to lower blood sugar in type 2 diabetes | Low blood sugar (hypoglycemia) — the main risk |
Can be combined with other diabetes drugs, like metformin | Weight gain |
Easy to take as a tablet | Nausea or diarrhea |
Works quickly | Skin rash or itching (rare) |
Relatively inexpensive compared with many other diabetes drugs | May become less effective over time |
[1]
Who should check with a doctor before taking a sulfonylurea?
If you have kidney disease or liver disease, ask your doctor before starting a sulfonylurea. These conditions can change how your body handles the medicine. [1]
How are sulfonylureas taken?
Sulfonylureas are taken as tablets, once or twice a day, in doses from 1 to 10 mg depending on the drug. [1]
Form: All sulfonylureas are tablets you swallow.
Strength: Doses range from 1 to 10 mg, depending on the drug.
How often: Once or twice a day.
With food: Your doctor may advise taking it just before or with a meal to lower the chance of low blood sugar.
Take exactly what your doctor prescribes — no more, no less.
What if you miss a dose of a sulfonylurea?
Missing a dose can let your blood sugar climb too high (hyperglycemia). Here's what to do:
Do | Don't |
Take the missed dose if you remember within a few hours and it's not close to your next dose | Double your next dose to "catch up" — this can cause dangerously low blood sugar |
Check your blood sugar more closely | Guess — ask your doctor or pharmacist if unsure |
[1]
Learn the warning signs of high blood sugar and when it becomes an emergency.
Can you overdose on sulfonylureas?
Yes. Taking more than prescribed can drop your blood sugar dangerously low. Severe signs include slurred speech, fainting and seizure — these need emergency help right away. [1]
What are the signs of low blood sugar on sulfonylureas?
Early signs of low blood sugar on sulfonylureas include shakiness, sweating, dizziness, confusion and blurred vision, while slurred speech, fainting and seizure are severe signs that need emergency help. Knowing these signs is one of the most important parts of taking a sulfonylurea safely. [1] [3]
Early warning signs | Severe warning signs |
Shakiness or trembling | Slurred speech |
Sweating | Fainting |
Dizziness | Seizure |
Confusion | |
Blurred vision |
[1]
For step-by-step treatment of a low, read our guide to diabetic hypoglycemia and how to treat it fast.
Which drugs interact with sulfonylureas?
Drugs that raise the risk of low blood sugar with sulfonylureas include azole antifungals, insulin, fluoroquinolone and tetracycline antibiotics, GLP-1 agonists, NSAIDs and warfarin. [1]
Medicine type | Examples / use |
Azole antifungals | Treat fungal infections |
Insulin | Diabetes treatment |
Fluoroquinolones and tetracyclines | Antibiotics for bacterial infections |
GLP-1 agonists | Diabetes and weight medicines — learn more |
NSAIDs | Pain and anti-inflammatory medicines |
Warfarin | Blood thinner |
[1]
Other medicines can make sulfonylureas less effective. Always tell your doctor about every medicine and supplement you take.
Can you drink alcohol while taking sulfonylureas?
You can drink alcohol, but it carries risks — alcohol can raise or lower blood sugar depending on the drink. If you drink: [1]
Don't drink on an empty stomach.
Limit how much you drink.
Choose low-sugar drinks.
Check your blood sugar.
Do sulfonylureas stop working?
Yes, sulfonylureas can become less effective over time, and if that happens your doctor will recommend another treatment. [1]
Regular follow-up visits and home blood sugar checks are how you'll catch this early. Other options your doctor may discuss include SGLT2 inhibitors and alpha-glucosidase inhibitors.
When should you call your doctor about sulfonylureas?
Call your doctor about sulfonylureas if your blood sugar readings are consistently too high or too low, you have signs of low blood sugar, or your health changes. See your doctor regularly so they can confirm your treatment is working, and call sooner if you have:
Blood sugar readings that are consistently too high or too low
Signs of low blood sugar, like shaking and sweating
Health changes such as surgery, pregnancy or starting new medicines
Get emergency help for slurred speech, fainting or a seizure. [1]
Conclusion
Sulfonylureas are simple, fast-acting and affordable tablets that help your pancreas release insulin to lower blood sugar in type 2 diabetes. They can be used alone or with other diabetes medicines.
The key to using them safely is knowing their main risk. Take your dose exactly as prescribed, never double up, learn the signs of low blood sugar, and keep checking your levels.
Want to stay on top of your diabetes care? Explore more plain-language, doctor-reviewed guides on Rinnit.com, starting with our complete diabetes guide — and bookmark Rinnit.com for trusted health updates you can act on.
FAQ
What are sulfonylureas used for?
Sulfonylureas treat type 2 diabetes. They lower blood sugar by helping the pancreas release more insulin.
Can sulfonylureas be used for type 1 diabetes?
No. Sulfonylureas are not a treatment option for type 1 diabetes.
What is the most common side effect of sulfonylureas?
The main risk is low blood sugar (hypoglycemia). Weight gain, nausea and diarrhea can also occur, and skin rash or itching is rare.
Can I take a sulfonylurea with metformin?
Yes. Sulfonylureas can be taken with other diabetes medicines, including metformin.
What should I do if I miss a dose?
Take it if you remember within a few hours and it isn't close to your next dose. Never double your next dose, and check your blood sugar closely.
Can I drink alcohol while taking a sulfonylurea?
Yes, but with care. Avoid drinking on an empty stomach, limit how much you drink, choose low-sugar drinks, and check your blood sugar.
Do sulfonylureas stop working over time?
They can become less effective over time. Regular check-ups and blood sugar monitoring help your doctor spot this and adjust treatment.
Are sulfonylureas safe for people with kidney or liver disease?
People with kidney or liver disease should ask their doctor before taking sulfonylureas.
Do sulfonylureas cause weight gain?
They can. Weight gain is a known side effect of sulfonylureas, so healthy eating and regular activity are important. Talk to your provider if your weight changes a lot.
What should I do if my blood sugar goes low on a sulfonylurea?
Eat or drink 15 grams of fast-acting sugar, such as 4 ounces of juice or glucose tablets, then recheck in 15 minutes and repeat if needed. Call 911 if the person is confused, cannot swallow safely or passes out.
Related reading on Rinnit
References
Cleveland Clinic. Sulfonylureas: Uses, Side Effects & How They Work. Cleveland Clinic. Last updated July 22, 2025. https://my.clevelandclinic.org/health/treatments/sulfonylureas
Varvaki Rados D, Catani Pinto L, Reck Remonti L, et al. The Association between Sulfonylurea Use and All-Cause and Cardiovascular Mortality: A Meta-Analysis with Trial Sequential Analysis of Randomized Clinical Trials. PLoS Med. 2016;13(4):e1001992. PMID 27071029. https://doi.org/10.1371/journal.pmed.1001992
Rosenstock J, Kahn SE, Johansen OE, et al. Effect of Linagliptin vs Glimepiride on Major Adverse Cardiovascular Outcomes in Patients With Type 2 Diabetes: The CAROLINA Randomized Clinical Trial. JAMA. 2019;322(12):1155-1166. PMID 31536101. https://doi.org/10.1001/jama.2019.13772
Douros A, Dell'Aniello S, Yu OHY, et al. Sulfonylureas as second line drugs in type 2 diabetes and the risk of cardiovascular and hypoglycaemic events: population based cohort study. BMJ. 2018;362:k2693. PMID 30021781. https://doi.org/10.1136/bmj.k2693
Medical disclaimer
This article is for general education only and is not a substitute for professional medical advice, diagnosis or treatment. Always talk with your doctor before starting, stopping or changing any diabetes medicine.
Comments