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.

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.

Who can and can't 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).

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?

Contact your local emergency service 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.

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 your local emergency service 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.

Call your local emergency service 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.

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.

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.

Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

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 for depression, St John's wort. It may change the way your body processes gliclazide.


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

Common questions