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  1. About gliclazide
  2. Key facts
  3. Who can and cannot take gliclazide
  4. How and when to take it
  5. Side effects
  6. How to cope with side effects
  7. Pregnancy and breastfeeding
  8. Cautions with other medicines
  9. Common questions

1. About gliclazide

Gliclazide is a medicine used to treat type 2 diabetes.

Type 2 diabetes is an illness where the body does not make enough insulin, or the insulin that's made does not work properly. This causes high blood sugar (hyperglycaemia).

Gliclazide lowers your blood sugar by increasing the amount of insulin your body produces.

Gliclazide is available on prescription. It comes as tablets.

2. Key facts

  • Gliclazide works by increasing the amount of insulin your body makes. Insulin is the hormone that controls the level of sugar in your blood.
  • If you take gliclazide once a day, it's best to take it in the morning with breakfast.
  • Gliclazide can sometimes make your blood sugar level too low (hypoglycaemia). Carry some sweets or fruit juice with you to help when this happens.
  • Gliclazide may contribute to weight gain.
  • Gliclazide may also be called by the brand names Bilxona, Dacadis, Diamicron, Laaglyda, Nazdol, Vamju, Vitile, Ziclaseg and Zicron.

3. Who can and cannot take gliclazide

Gliclazide is only for adults. Do not give this medicine to children under 18 years.

Gliclazide is not suitable for some people. Tell your doctor before starting the medicine if you:

  • have had an allergic reaction to gliclazide or any other medicines in the past
  • have ketone bodies and sugar in your urine (diabetic ketoacidosis)
  • have severe kidney or liver disease
  • have a rare illness called porphyria
  • are taking miconazole (a treatment for fungal infections)
  • are breastfeeding
  • have an illness called G6PD-deficiency
  • need to have surgery

This medicine is not used to treat type 1 diabetes (when your body does not produce insulin).

4. How and when to take it

The dose of gliclazide can vary. Take this medicine as prescribed by your doctor.

Swallow your gliclazide tablets whole with a glass of water. Do not chew them.

Different types of gliclazide tablets

Gliclazide comes as 2 different types of tablets: normal (standard release) and long acting (slow release).

Standard-release tablets release gliclazide into your body quickly, so you may need to take them several times a day depending on your dose.

Slow-release tablets dissolve slowly, which means you do not have to take them as regularly as the standard ones. One dose in the morning is usually enough.

Your doctor or pharmacist will explain what type of gliclazide tablets you're on and how often to take them.

How much to take

For standard-release gliclazide, the maximum daily dose is 320mg (4 x 80mg tablets).

If you need to take more than 160mg (2 x 80mg tablets) a day, take the tablets twice a day with your morning and evening meals.

For slow-release gliclazide, the maximum daily dose is 120mg. Take your dose once a day before breakfast.

Will my dose go up or down?

Your doctor will check your blood sugar levels regularly and may adjust your dose of gliclazide if necessary.

What if I forget to take it?

If you miss a dose of gliclazide, take the next dose at the usual time. Do not take a double dose to make up for a forgotten dose.

If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Urgent advice: Contact your doctor straight away if:

  • you take too many gliclazide tablets

An overdose of gliclazide can cause low blood sugar.

If you think you have low blood sugar, have some food or drink that quickly gets sugar into your bloodstream, such as sugar cubes or fruit juice.

This type of sugar will not last long in your blood, so you may also need to eat a starchy carbohydrate, like a sandwich or a biscuit.

5. Side effects

Like all medicines, gliclazide can cause side effects, although not everyone gets them.

Side effects can be less likely if you take gliclazide tablets with a meal.

Common side effects

Talk to your doctor or pharmacist if these side effects bother you or do not go away:

  • stomach ache or indigestion
  • feeling sick (nausea)
  • being sick (vomiting) or diarrhoea
  • constipation

Serious side effects

Serious side effects are rare.

Call a doctor straight away if you get:

  • yellow skin or the whites of your eyes turn yellow - these can be signs of a liver problem
  • paleness, prolonged bleeding, bruising, sore throat and fever - these can be signs of a blood disorder
  • a rash, redness, itching and hives, sudden swelling of eyelids, face, lips, mouth, tongue or throat that may make it hard to breathe - these can be signs of a skin disorder called angioedema

Your eyesight may be affected for a short time, especially at the start of treatment, because of changes in your blood sugar levels.

Low blood sugar

Gliclazide can sometimes cause your blood sugar to go too low. The name for this is hypoglycaemia, or a "hypo".

Early warning signs of low blood sugar include:

  • feeling hungry
  • trembling or shaking
  • sweating
  • confusion
  • difficulty concentrating

It's also possible for your blood sugar to go too low while you're asleep. If this happens, it can make you feel sweaty, tired and confused when you wake up.

Low blood sugar may happen if you:

  • take too much gliclazide
  • eat meals irregularly or skip meals
  • are fasting
  • do not eat a healthy diet and are not getting enough nutrients
  • change what you eat
  • increase your physical activity without eating more to compensate
  • drink alcohol, especially after skipping a meal
  • take some other medicines or natural remedies at the same time
  • have a hormone disorder, such as hypothyroidism
  • have kidney or liver problems

To prevent hypos, it's important to have regular meals, including breakfast. Never miss or delay a meal.

If you're planning to exercise more than usual, make sure you eat carbohydrates like bread, pasta or cereals before, during or afterwards.

Always carry a fast-acting carbohydrate with you, like sugar cubes, fruit juice or some sweets, in case your blood sugar level gets low. Artificial sweeteners will not help.

You may also need to eat a starchy carbohydrate, like a sandwich or a biscuit, to maintain your blood sugar for longer.

If taking in sugar does not help or the hypo symptoms come back, contact your doctor or the nearest hospital.

Make sure your friends and family know about your diabetes and the symptoms of low blood sugar levels so they can recognise a hypo if it happens.

Serious allergic reaction

It's possible to have a serious allergic reaction (anaphylaxis) to gliclazide.

Immediate action required: Call 999 or go to A&E now if:
  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

You could be having a serious allergic reaction and may need immediate treatment in hospital.

These are not all the side effects of gliclazide.

For a full list, see the leaflet inside your medicines packet.


You can report any suspected side effect using the Yellow Card safety scheme.

Visit Yellow Card for further information.

6. How to cope with side effects

What to do about:

  • stomach ache or indigestion - try to rest and relax. It can help to eat and drink slowly, and have smaller and more frequent meals. Putting a heat pad or covered hot water bottle on your stomach may also help. If you're in a lot of pain, speak to your pharmacist or doctor.
  • feeling sick (nausea) - take your tablets with a meal. Stick to simple meals and avoid rich or spicy food.
  • being sick (vomiting) or diarrhoea - drink lots of fluids, such as water or squash, to avoid dehydration. Take small, frequent sips if you're being sick. Speak to a pharmacist if you have signs of dehydration, such as peeing less than usual or having dark, strong-smelling pee. Do not take any other medicines to treat diarrhoea or vomiting without speaking to a pharmacist or doctor.
  • constipation - eat more high-fibre foods, such as fresh fruit and vegetables and cereals, and drink plenty of water. Also do some exercise by going for a daily walk or run, for example.

7. Pregnancy and breastfeeding

Gliclazide is not generally recommended in pregnancy and while breastfeeding.

It's not clear whether gliclazide harms an unborn baby. For safety, your doctor will probably change your medicine to insulin before you become pregnant or as soon as you find out you're pregnant.

Gliclazide and breastfeeding

If you take gliclazide while breastfeeding, there's a risk of your baby getting low blood sugar.

Talk to your doctor if you want to breastfeed.

Non-urgent advice: Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

8. Cautions with other medicines

There are some medicines that interfere with the way gliclazide works.

Tell your doctor if you're taking any of these medicines:

  • steroid tablets, such as prednisolone
  • some medicines used to treat heart problems and high blood pressure
  • medicines to treat bacterial or fungal infections, such as clarithromycin or fluconazole
  • painkillers, such as ibuprofen and aspirin (but not paracetamol)
  • medicines used to treat asthma, such as salbutamol
  • male and female hormones, such as testosterone, oestrogen and progesterone
  • other diabetes medicines

Gliclazide may also increase the effects of medicines that thin your blood, such as warfarin.

Some women might need a small adjustment in their gliclazide dose after starting contraceptive pills, as in rare cases they can increase blood sugar levels.

Mixing gliclazide with herbal remedies and supplements

Do not take the herbal remedy St John's wort (sometimes taken for depression). It may change the way your body processes gliclazide.

Important: Medicine safety

Tell your doctor or pharmacist if you're taking any other medicines, including herbal medicines, vitamins or supplements.

9. Common questions

How does gliclazide work?

Gliclazide is a type of medicine known as a sulfonylurea.

Sulfonylureas increase the amount of insulin that your pancreas makes.

Insulin is the hormone that controls the level of sugar in your blood.

When will I feel better?

You may not have had any symptoms of diabetes, so you will not necessarily feel any different when you take gliclazide.

This does not mean that gliclazide is not working and it's important to keep taking it.

Gliclazide will help keep your blood sugar level stable and reduce your chances of diabetes-related problems in the future.

How long will I take gliclazide for?

Treatment for diabetes is usually for life.

Do not stop taking your gliclazide tablets without talking to your doctor.

Can I take gliclazide for a long time?

Gliclazide is safe to take for a long time. There's no evidence it harms your pancreas or your general health.

But gliclazide may stop working properly after a while.

Your doctor may then want to stop it or add a different medicine to help keep your blood sugar level stable.

What will happen if I come off gliclazide?

Do not stop taking gliclazide without talking to your doctor.

If you stop taking gliclazide suddenly, your diabetes may get worse.

Will I put on weight?

Gliclazide can make you hungrier and retain water, so it can be quite challenging to avoid putting on weight while you're taking it.

Try to eat a healthy, balanced diet without increasing your portion sizes so you do not gain too much weight.

Regular exercise will also help keep your weight stable.

Can I get diabetes medicines for free?

If you have diabetes, you're entitled to free prescriptions for all of your medicines, not just your diabetes ones.

To claim your free prescriptions, you'll need to have a medical exemption certificate.

The application form for the medical exemption certificate is called FP92A. You can get this from your doctor's surgery.

You will need to fill in the form, then your doctor will sign it and send it off.

How does it compare with other diabetes medicines?

There are other groups of medicines that can lower blood sugar levels:

Gliclazide can be prescribed on its own or in combination with the above medicines.

It's usually prescribed if you cannot take metformin, or if metformin is no longer keeping your blood sugar level under control when used by itself.

Gliclazide is a sulfonylurea. There are 4 other sulfonylureas available:

These all work in the same way: by increasing the amount of insulin your body produces.

Can I take painkillers with gliclazide?

It's safe to take paracetamol with gliclazide.

Do not take aspirin or ibuprofen. These painkillers can interfere with gliclazide and lower your blood sugar levels too much.

Can I drive or ride a bike?

If your blood sugar levels are stable, your ability to drive, cycle or use machines or tools should not be affected by gliclazide.

But if your blood sugar levels become too low, this can reduce your concentration.

If this happens to you, do not drive, cycle or use machines or tools until you feel better.


Do not drive or use machines or tools if you start to feel the symptoms of low blood sugar.

Will it affect my fertility?

There's no firm evidence to suggest that taking gliclazide will reduce fertility in either men or women.

But speak to a pharmacist or your doctor before taking it if you're trying to get pregnant.

Will it affect my contraception?

Gliclazide does not interfere with any type of contraception.

Some women might need their gliclazide dose adjusting if they start taking the combined pill.

This is because contraceptive pills can occasionally increase blood sugar levels.

Can I drink alcohol with it?

Yes, you can drink alcohol while taking gliclazide, but it's best for men and women to drink no more than 2 units a day.

Drinking more than this can increase the risk of low blood sugar.

Try to keep to the recommended guidelines of no more than 14 units of alcohol a week.

A standard glass of wine (175ml) is 2 units. A pint of lager or beer is usually 2 to 3 units of alcohol.

Is there any food or drink I need to avoid?

It's a good idea to cut down on foods with added sugar.

Check the nutrition labels as many foods and drinks are high in sugar, such as:

  • sweets
  • cakes
  • biscuits
  • chocolate
  • some fizzy drinks
  • juice drinks

Be careful eating food and drink containing karela, as it can lower your blood sugar levels and mean your diabetes is not controlled as well as it should be.

Karela (also called bitter gourd) is used to flavour foods, such as curries like bitter gourd masala.

It has a bitter taste and is also made into juice and tea.

Can I take gliclazide before surgery?

If you're going to have an operation, tell the doctor you're taking gliclazide.

This is because gliclazide increases your risk of low blood sugar during the operation.

Low blood sugar can be difficult to detect when a general anaesthetic (that puts you to sleep) is used.

For a few days around the time of your operation, your doctor may temporarily switch you to insulin instead.

Can lifestyle changes help my diabetes?

There are some lifestyle changes you can make to help control the symptoms of diabetes.

These include: