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Sulphonylureas are a type of medication you might need to take if you have type 2 diabetes.  

How do sulphonylureas work? 

Sulphonylureas work by helping your pancreas to make more insulin. They also help insulin to work more effectively in the body. This all helps to lower blood sugar levels.   

Different types of sulphonylureas 

There are four types of sulphonylureas that people living with type 2 diabetes in the UK can be prescribed.  


Gliclazide comes as standard-release or slow-release tablets which you take at the same time once a day before breakfast.  

There are many different brands of Gliclazide available, such as Diamicron, Glydex and Zicron. All medication boxes will include the name of the actual drug as well as the brand name, so make sure the packaging also says Gliclazide, especially if the box looks different to your usual medication. 


Glipizide is a tablet that you take once a day, and you must take it 30 minutes before breakfast or lunch. If you take a higher dose of glipizide, then you might take this more than once a day. It has the brand name Minodiab.  


Glimepiride is a tablet that you take once daily just before or with your first meal of the day. 


Tolbutamide is a tablet that can be taken once a day with or straight after your first meal of the day, or in smaller doses throughout the day with meals.   

There is another sulphonylurea called Glibenclamide, which is used to treat adults with neonatal diabetes. Glibenclamide is a tablet that should be taken with or immediately after your first main meal of the day. It has the brand name Glyburide.  

Always take your sulphonylurea exactly as your healthcare professional has told you. The Patient Information Leaflet inside the box will tell you how to take it but you can always check with your healthcare team if you’re not sure. 

Who can take sulphonylureas? 

Adults over 18 years with type 2 diabetes can take sulphonylureas. These drugs can be taken on their own as an alternative to metformin or with other diabetes medications.    

Who can’t take sulphonylureas? 

Some medications might not be suitable for some people, which might be because of medical conditions or other reasons:   

  • Your healthcare professional will tell you to stop taking a sulphonylurea if you develop diabetic ketoacidosis, also called DKA; 
  • You might not be able to take gliclazide and tolbutamide if you have a condition called acute porphyria; 
  • If you have kidney disease you might not be able to take sulphonylureas, or you might need to reduce your dose, but this will depend on the stage of your kidney disease; 
  • If you have severe liver disease you might also not be able to have gliclazide; 
  • You should not use sulphonylureas if you are pregnant of breastfeeding. If you’re planning a pregnancy speak with a healthcare professional if you are using this medication; 
  • You might need to temporarily stop taking a sulphonylurea if you’re going to have an operation. 

When you start a new medication always check with your healthcare team that it’s suitable for you to take.   

Your prescription 

The sulphonylurea you may be prescribed could be standard-release or slow-release tablets. They work in the body in different ways, but they contain the same medication.  

Your healthcare professional should explain your prescription to you but it's important to make sure you ask if you don't feel you know enough.   

And make sure you talk to your GP or your diabetes team if you struggle to take your sulphonylurea. They might be able to help by giving you a different dose.   

In England, if you need to take any medication to manage your diabetes, your prescriptions will be free. Ask your healthcare team about a prescription exemption certificate if you don't have one, to make sure you don't get charged for your medication. Prescriptions are already free for everybody in the rest of the UK, so you shouldn't pay for your sulphonylurea. 

Sulphonylureas side effects 

Like all medicines, sulphonylureas can cause side effects. But when side effects are listed as common in the Patient Information Leaflet, it doesn’t mean that everyone who takes the medication will get them. 

The information about side effects is based on the likelihood of people having them. For example, if a side effect is very common then it can affect more than one in ten people, and if a side effect is very rare then it affects fewer than one in 10,000 people.  

Because medicines can affect people differently, your healthcare team will speak to you about what’s best for you and discuss any side effects.    

One of the most common side effects of sulphonylureas is low blood sugar, also called hypoglycaemia, or a hypo. This is where the level of sugar in your blood drops too low, below 4mmol/l.   

Other common side effects can include: 

  • tummy ache 
  • sickness 
  • diarrhoea.  

Some people find that they gain weight while taking a sulphonylurea. Eating a healthy, balanced diet and physical activity can help you to manage weight gain.  

These aren’t all the side effects. You will find a full list of known side effects in the Patient Information Leaflet which comes in the medication box.   

It’s also important to take individual advice from your healthcare team before starting treatment with sulphonylureas and report any side effects, if you have any.  

You can also report these side effects to the Yellow Card Scheme, which is the government system used for recording side effects with medicines in the UK.   

Driving and sulphonylureas 

Sulphonylureas can increase the risk of hypos while driving.  

Speak to your healthcare team if you’re not sure whether you’re at risk of having these and what you can do to prevent them. 

More information and support 

Still have more questions? Or is there anything you're not sure about sulphonylureas after reading this page? Contact our helpline on 0345 123 2399. 

You can visit the NHS website for more information on sulphonylureas.

Next Review Date
Content last reviewed
18 June 2024
Next review due
18 June 2027
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