• Take metformin just after a meal or with a snack.
  • The most common side-effects of this treatment are feeling sick, diarrhoea and abdominal pain. These symptoms do not usually last long.
  • Keep your regular appointments with your doctor and clinics. This is so your progress can checked.
Type of medicine Oral biguanide antidiabetic medicine
Used for Type 2 diabetes mellitus
Also called Bolamyn® SR
Glucophage® SR
Metabet® SR
Available as Tablets or modified-release tablets
Oral sugar-free solution
Powder for oral solution (sachets)

Insulin is a hormone that is made naturally in your body, in the pancreas. It helps to control the levels of sugar in your blood. If your body does not make enough insulin to meet its needs, or if it does not use the insulin it makes effectively, this results in the condition called diabetes mellitus (sugar diabetes).

People with diabetes need treatment to control the amount of sugar in their blood. This is because good control of blood sugar levels reduces the risk of complications later on. Some people can control the sugar in their blood by making changes to the food they eat, but for other people, medicines like metformin are given alongside the changes in diet. Metformin allows the body to make better use of the lower amount of insulin which occurs in the kind of diabetes mellitus known as type 2 diabetes.

Metformin can be given on its own or alongside other antidiabetic medicines or insulin.

Before taking metformin make sure your doctor or pharmacist knows:

  • If you have kidney or liver problems.
  • If you are dehydrated or have a severe infection.
  • If you have recently had severe heart or breathing problems.
  • If you have recently had an X-ray where a dye was injected.
  • If you have previously had a serious problem with your diabetes, called 'diabetic ketoacidosis'. (When you have this you feel thirsty, sick, weak, breathless and lose weight quickly.)
  • If you drink a lot of alcohol.
  • If you are pregnant or breast-feeding.
  • If you have ever had an allergic reaction to this or to any other medicine.
  • If you are taking other medicines, including those available to buy without a prescription, herbal and complementary medicines.
  • Before starting this treatment, read the manufacturer's printed information leaflet from inside the pack.
  • Take metformin exactly as your doctor has told you.
  • When you first start this treatment your doctor may give you a small dose and then gradually increase it. This allows your doctor to make sure that you have the dose that is right for you and helps to avoid any unwanted symptoms.
  • Try to take metformin at the same time(s) each day to avoid missing any doses. Take your doses just after eating a meal or with a snack.
  • If you do forget to take a dose, take it as soon as you remember unless it is nearly time for your next dose, in which case leave out the missed dose. Do not take two doses together to make up for a forgotten dose.
  • If you have been given modified-release metformin tablets (these have 'SR' after the name of the tablet), the tablets are designed to release metformin slowly. You must swallow these tablets whole. Do not crush or chew the tablets, as you your body may absorb the metformin too quickly.
  • If you have been given metformin sachets, pour the powder from the sachet into a glass and add 150 ml of water. Stir the solution to mix it, and then drink it straightaway.
  • It is important that you keep your regular doctor's and clinic appointments. This is so that your progress can be monitored. You are likely to need regular check-ups with an eye clinic and a foot clinic as well as with your doctor and diabetes clinic.
  • Your doctor may recommend that you test for sugar in your blood or urine regularly to check that your diabetes is being controlled. Your doctor or diabetes nurse will show you how to do this.
  • If you have been given advice by your doctor about changes to your diet, stopping smoking or taking regular exercise, it is important for you to follow the advice you have been given.
  • Check with your doctor before taking up any new physical exercise, as this will have an effect on your blood sugar levels and you may need to check your blood or urine levels more regularly.
  • Drinking alcohol is not recommended with metformin but, if you do have a drink, keep to the recommended alcohol limits. Taking metformin and alcohol will affect the control of your blood sugar.
  • If you are due to have an operation or dental treatment, you should tell the person carrying out the treatment that you are diabetic and taking metformin.
  • If you get unusually thirsty, pass urine more frequently, and feel very tired, then let your doctor know. Your dose of metformin may need adjusting.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. These usually improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following side-effects continue or become troublesome.

Common metformin side-effects What can I do if I experience this?
Feeling sick or being sick This is a common problem but it usually improves after a few days. If it continues, speak with your doctor
Diarrhoea Drink plenty of water to replace any lost fluids. This usually improves as your body adjusts to metformin, but you should let your doctor know if it continues
Unusual taste, lack of appetite, abdominal pain If these become troublesome, speak with your doctor

Important: if you get the following rare but serious side-effects, contact your doctor or go to the accident and emergency department of your local hospital straightaway - you may be experiencing a rare reaction to metformin, called lactic acidosis:

  • Very fast, gasping, breathing.
  • Feeling very unwell and being sick.
  • Feeling dizzy, cold and confused.

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.
  • If you buy any medicines check with a pharmacist that they are safe to take with your other medicines.
  • Never take more than the prescribed dose. If you suspect that someone has taken an overdose of this medicine go to the accident and emergency department of your local hospital at once. Take the container with you, even if it is empty.
  • This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.
  • Never keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.
  • If you have any questions about this medicine ask your pharmacist.

Further reading & references

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Craig Foster
Current Version:
Peer Reviewer:
Dr Helen Huins
Last Checked:
Document ID:
1075 (v25)
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