Endocrine / Diabetes
Sulfonylureas
e.g. gliclazide — Oral diabetes drugs that lower glucose quickly but can cause hypos and weight gain.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
What it is
Sulfonylureas are an established oral treatment for type 2 diabetes, often added when metformin alone is not enough or used where cost and rapid effect matter.
How it works
They stimulate the pancreas to release more insulin. Because that effect happens regardless of the current glucose level, they can push glucose too low — which is why hypoglycaemia is a real risk.
In practice
In practice sulfonylureas work fast and are inexpensive, which keeps them useful, but unlike metformin they can cause hypoglycaemia and weight gain. That matters most in older people, those who skip meals, drivers and those with renal impairment, where hypos can be prolonged. Counsel every patient on recognising and treating a hypo, and review the choice as newer agents with better safety profiles become available.
Examples
Practical use
How to take it & use it well
- Take sulfonylureas such as gliclazide with or just before a meal, usually in the morning, so they match your body's response to food.
- Eat regular meals and do not skip them, as missing food while on these medicines can cause low blood sugar.
- Carry a fast-acting sugar source in case you feel a hypo coming on, with symptoms like shakiness, sweating or confusion.
- If you miss a dose, only take it if you are about to eat; otherwise skip it rather than risk a hypo later; never double up.
- Take it at the same times each day to keep your blood sugar steady.
- Tell your team if you are unwell or eating less, as your dose may need adjusting.
Common uses
- Type 2 diabetes (add-on or where rapid effect/low cost is needed)
Monitoring
- HbA1c and any hypoglycaemia
- Renal function
- Weight
Weighing it up
Advantages & disadvantages
Advantages
- They lower blood sugar effectively in type 2 diabetes.
- They work quickly compared with some other diabetes medicines.
- They are well established, inexpensive and widely used.
- They are taken by mouth, often once or twice a day.
- They can be combined with several other diabetes treatments.
Disadvantages
- They can cause low blood sugar, especially if meals are missed or delayed.
- They often lead to some weight gain.
- Their effect can lessen over time as diabetes progresses.
- They are less suitable for people who eat irregularly or are at high risk of hypos.
- Care is needed in older adults and those with reduced kidney function, who are more prone to low sugars.
Key safety principles
What to watch for
- Hypoglycaemia — can be prolonged, particularly in the elderly and in renal impairment.
- Weight gain is common.
- Caution with missed meals, alcohol and driving.
Key interactions
What to avoid or check alongside
- Alcohol can increase the risk and mask the warning signs of low blood sugar.
- Combined with insulin or other glucose-lowering medicines, the risk of hypos rises.
- Some other medicines can either strengthen or weaken their blood-sugar effect, so a medicines check helps.
- Certain antibiotics and antifungals can increase the risk of low blood sugar when taken together.
- Skipping meals while taking them makes hypos more likely, so regular eating matters.
Patient & carer advice
- Learn to recognise and treat a "hypo" and carry fast-acting sugar
- Do not skip meals
- Be careful with alcohol and check driving advice
Use with
Related clinical calculators
Dose and risk decisions for this class often depend on renal function, weight or bleeding/stroke risk. These tools help:
Answers
Sulfonylureas: frequently asked questions
What is a hypo and how do I treat it?
A hypo is low blood sugar, with signs like shakiness, sweating, hunger or confusion. Treat it quickly with a fast-acting sugar, then a longer-lasting snack, and tell your team if it happens often.
Why might I gain weight on this medicine?
Sulfonylureas can encourage weight gain partly by increasing insulin activity. Healthy eating and activity help manage this; discuss concerns with your team.
Can I skip a dose if I am not eating?
If you are not going to eat, it is often safer to skip that dose to avoid a hypo. Check the specific advice for your situation with your prescriber.
Does alcohol affect this medicine?
Yes. Alcohol can raise the risk of low blood sugar and hide its warning signs, so drink sensibly and not on an empty stomach.
Will it keep working forever?
Its effect can fade over the years as type 2 diabetes progresses, and your treatment may need adjusting or adding to over time.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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