Lyng Pharmacy
Medicines A–Z · Sulfonylurea (diabetes)

Gliclazide

A sulfonylurea for type 2 diabetes · Written by the Lyng Pharmacy team, based on NHS and BNF guidance · Updated August 2026
Also sold asDiamicron
Type of medicineSulfonylurea (diabetes)
Available asTablets, modified-release tablets
How you get itPrescription only

Gliclazide makes the pancreas release more insulin. That is effective and cheap, and it is also why gliclazide — unlike metformin — can cause hypoglycaemia. If you have been moved onto it, the hypo advice is the part to read properly.

How to take it

Standard tablets are usually taken with breakfast, or with breakfast and the evening meal if twice daily. Modified-release tablets are taken once daily with breakfast and must be swallowed whole.

Take it with food, not on an empty stomach. Skipping meals while taking gliclazide is the classic route to a hypo.

Hypoglycaemia — what to know

Low blood sugar signs: shakiness, sweating, hunger, tingling lips, palpitations, confusion, irritability, difficulty concentrating.

Treat a hypo immediately with fast-acting sugar — glucose tablets, 150ml of ordinary (not diet) fizzy drink or fruit juice — then follow with a longer-acting carbohydrate such as a sandwich or biscuits. Recheck after 15 minutes and repeat the fast sugar if still low.

Hypos are more likely if you skip meals, exercise more than usual, drink alcohol (particularly without food), or have kidney or liver problems.

You must tell the DVLA if you are treated with a sulfonylurea and you drive. Test your blood glucose before driving and every two hours on long journeys, and keep fast-acting sugar in the car.

Side effects and cautions

Weight gain is common. Other effects include nausea, stomach upset and, less often, rash.

Get medical advice for yellowing of the eyes or skin, unusual bruising or bleeding, or repeated hypos — which usually means the dose needs reviewing rather than that you need to eat more.

Tell your prescriber about beta blockers (which can mask hypo warning signs), warfarin, some antibiotics, and steroids.

Gliclazide is not usually used in pregnancy — speak to your diabetes team if you are planning one.

Always read the label. This page is general information, not advice for your situation. Doses, warnings and interactions differ between products and between people. Check the leaflet inside your medicine, and ask our pharmacist if anything is unclear — that conversation is free and takes two minutes.

Questions about Gliclazide?

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Frequently asked questions

Can gliclazide cause low blood sugar?
Yes — unlike metformin, it can. Skipping meals, extra exercise and alcohol all increase the risk. Always carry fast-acting sugar.
When should I take gliclazide?
With breakfast, or with breakfast and the evening meal if twice daily. Never on an empty stomach.
Do I need to tell the DVLA I take gliclazide?
Yes. Sulfonylureas carry a hypo risk, so the DVLA must be informed, and you should test your glucose before driving.
Does gliclazide cause weight gain?
Weight gain is a common effect. If it is a problem, discuss alternatives with your diabetes team.

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