Metformin for diabetes

Take metformin just after a meal or with a snack.

The most common side-effects are feeling sick, diarrhoea and tummy (abdominal) pain. These symptoms usually pass after the first few days of treatment.

Keep your regular appointments with your doctor and clinics. This is so your progress can be checked.

Type of medicine A biguanide antidiabetic medicine
Used for Type 2 diabetes mellitus
Also called Bolamyn®; Diagemet®; Glucient®; Glucophage®; Metabet®; Sukkarto®
Available as Tablets and modified-release tablets; oral liquid medicine; sachets of powder

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

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 known as type 2 diabetes.

Metformin can be given on its own, or alongside insulin or another antidiabetic medicine. There are a number of tablets available which contain metformin in combination with one of these other antidiabetic medicines (brands include Jentadueto®, Competact®, Komboglyze®, Janumet®, and Eucreas®). Taking a combination tablet like these can help to reduce the total number of tablets that need to be taken each day.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking metformin it is important that your doctor knows:

  • If you have any problems with the way your kidneys work or with the way your liver works.
  • If you have recently been severely unwell.
  • If in the previous two days you have had an X-ray where a dye was injected.
  • If you are pregnant or breast-feeding. (Metformin can be taken whilst pregnant or feeding a baby, but it is important that your doctor knows about it.)
  • If you have ever had an allergic reaction to a medicine.
  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about metformin and will provide you with a full list of the side-effects which you may experience from taking it.
  • Take metformin exactly as your doctor tells you to. You will be started on a low dose (usually one dose a day) and then your dose will gradually be increased. This allows your doctor to make sure that you have the dose that is right for you, and also helps to reduce the risk of unwanted side-effects.
  • Try to take metformin at the same time(s) each day, as this will help you to remember to take it regularly. Take your doses during a meal or just after a snack.
  • If you have been given modified-release metformin tablets (these have the letters 'SR' or 'XL' after the brand name), the tablets are designed to release metformin slowly and evenly. You must swallow these tablets whole - do not break or chew the tablets, as 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.
  • If you forget to take a dose, make sure that you remember to take your next dose when it is due. Do not take two doses together to make up for a forgotten dose.
  • It is important that you keep your regular doctor's and clinic appointments. This is so your progress can be monitored. You will 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 (glucose) 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.
  • Do not drink alcohol, as it can affect the control of your blood sugar and can increase the risk of lactic acidosis (see below).
  • 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.
  • Make sure you know what it feels like if your blood sugar is low. This is known as hypoglycaemia, or a 'hypo'. Although metformin is unlikely to cause low blood sugar, other medicines that you are taking for diabetes alongside it may. The first signs of hypoglycaemia are feeling shaky or anxious, sweating, looking pale, feeling hungry, having a feeling that your heart is pounding (palpitations), and feeling dizzy. If you are a driver you should take special care, as your ability to concentrate may be affected if your diabetes is not well controlled. You may be advised to check your blood sugar levels before you travel and have a snack with you on long journeys.
  • If you are due to have an operation or any medical treatment, you should tell the person carrying out the treatment that you have diabetes and that you are taking metformin.
  • If you get unusually thirsty, pass urine more frequently, and feel very tired, you should let your doctor know. These are signs that there is too much sugar in your blood and your treatment may need adjusting.
  • Treatment for diabetes is usually lifelong. Continue to take metformin unless you are advised otherwise by your doctor.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with metformin. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Very common metformin side-effects (these affect more than 1 in 10 people)
What can I do if I experience this?
Feeling sick or being sick Remember to take your doses after food. This usually improves after a few days, but if it continues, speak with your doctor for further advice
Diarrhoea Remember to take your doses after food and drink plenty of water to replace any lost fluids. This usually improves after a few days, but if it continues, speak with your doctor for further advice
Unusual taste, lack of appetite, tummy (abdominal) pain If these become troublesome, speak with your doctor

Important: your doctor will discuss with you the possibility of a side-effect called lactic acidosis. Although this occurs only rarely, it is a serious condition. Let a doctor know straightaway if you are being sick or feel very unwell, or if you become unusually tired, or if you feel short of breath and your breathing becomes faster than normal.

If you experience any other symptoms which you think may be due to metformin, speak with your doctor or pharmacist for further advice.

  • 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, always 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 you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. 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.

Do not 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

  • British National Formulary; 67th Edition (March 2014) British Medical Association and Royal Pharmaceutical Society of Great Britain, London

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 Hannah Gronow
Document ID:
1075 (v26)
Last Checked:
20/09/2014
Next Review:
19/09/2017
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