What is a Patient Information Leaflet and why is it useful?

The Patient Information Leaflet (PIL) is the leaflet included in the pack with a medicine. It is written for patients and gives information about taking or using a medicine. It is possible that the leaflet in your medicine pack may differ from this version because it may have been updated since your medicine was packaged.

Below is a text only representation of the Patient Information Leaflet. The original can be viewed in PDF format using the link above.

The text only version may be available from RNIB in large print, Braille or audio CD. For further information call RNIB Medicine Leaflet Line on 0800 198 5000. The product code(s) for this leaflet is: PL 17780/0081.

Metformin 500mg and 850mg Tablets

PACKAGE LEAFLET: INFORMATION FOR THE USER

METFORMIN 500MG AND 850MG TABLETS

Read all of this leaflet carefully before you start taking this medicine.

  • Keep this leaflet. You may need to read it again.
  • If you have further questions, please ask your doctor or your pharmacist.
  • This medicine has been prescribed for you. Do not pass it on to others. It may harm them, even if their symptoms are the same as yours.
  • If any of the side effects get serious, or if you notice any side effects not listed in this leaflet, please tell you doctor or pharmacist.
  • Your doctor may have given you this medicine before from another company. It may have looked slightly different. However, either brand will have the same effect.

In this leaflet:

1. What metformin is and what it is used for
2. Before you take metformin
3. How to take metformin
4. Possible side effects
5. How to store metformin
6. Further information

1. WHAT METFORMIN IS AND WHAT IT IS USED FOR

The name of this medicine is Metformin 500mg or 850mg Tablets (called metformin in this leaflet). It belongs to a group of medicines called biguanides (a type of oral hypoglycaemic).

Metformin is used for the sort of diabetes called Type 2 diabetes or non-insulin-dependent diabetes mellitus.

How metformin works

  • In type 2 diabetes, there is too much sugar (glucose) in your blood. This is because your body does not make enough insulin or because it makes insulin that does not work properly.
  • Insulin is a hormone that allows your body tissue to take glucose from the blood and use it for energy or for storage for future use.
  • Metformin works by improving the sensitivity of your body to insulin. It helps your body to use glucose in the normal way again

Using this medicine

  • This medicine is given when diet and exercise alone has not been able to control your blood sugar levels.
  • Metformin can be given on its own. However, sometimes it is given with other medicines for diabetes or with insulin.
  • In patients who are overweight, long-term use of metformin also helps to lower the risk of any problems related to diabetes

2. BEFORE YOU TAKE METFORMIN

Do not take Metformin if:

  • you are allergic (hypersensitive) to metformin or any of the other ingredients in this liquid (see section 6: Further information). An allergic reaction can include a rash, itching or shortness of breath.
  • you have recently had a heart attack or any other heart problems
  • you have severe circulation problems or difficulty in breathing
  • you have liver or kidney problems
  • you have had serious problems with your diabetes in the past called diabetic ketoacidosis. When you have this you lose weight quickly, feel sick (nausea) or are sick (vomiting). See also in Section 4: Possible side effects
  • you have recently had a severe infection, injury or trauma (shock)
  • you are dehydrated
  • you are going to have an X-ray where you will be injected with a dye
  • you are a heavy drinker of alcohol (more than 21 units a week for a man or 14 units a week for a woman). A unit is equivalent to a small glass of wine, one shot or half a pint of beer.
  • you are pregnant, planning to get pregnant or are breast-feeding (see Pregnancy and Breast-feeding).

Do not take this medicine if any of the above applies to you. If you are not sure, talk to your doctor or pharmacist before taking metformin.

Take special care and check with your doctor or pharmacist before taking metformin if:

  • You are elderly
  • You are on a very low calorie diet (less than 1000 calories a day) or are fasting. This could increase the chances of you getting a very rare, but serious side effect called lactic acidosis (see section 4)

If any of the above apply to you (or you are not sure), talk to your doctor or pharmacist before taking metformin.

Operations and tests while taking metformin

  • The amount of sugar in your blood or urine should be checked regularly. Your doctor will also check your kidneys are working properly. This should be done at least once a year (more often if you are elderly or have kidney problems).
  • If you are going to have an X-ray, tell your doctor you are taking metformin. If this involves having a dye injected, you must stop taking metformin.
  • If you are going to have an operation that needs a general anaesthetic, tell your doctor you are taking metformin before the operation. Your doctor may stop you taking metformin for a couple of days before and after the operation

Taking metformin with other medicines

Please tell your doctor or pharmacist if you are taking or have recently taken any other medicine. This includes medicines obtained without a prescription, including herbal medicines. This is because metformin can affect the way some other medicines work. Also, some medicines can affect the way metformin works.

In particular, tell your doctor or pharmacist if you are taking any of the following medicines:

  • Medicines for high blood pressure (hypertension) such as water tablets (diuretics), ACE inhibitors (such as enalapril)
  • Medicines for asthma such as salbutamol or formoterol (beta-2-agonists)
  • Medicines used for inflammation called steroids

If any of the above apply to you (or you are not sure), talk to your doctor or pharmacist before taking metformin.

Taking metformin with food and drink

  • You need to eat carbohydrates regularly throughout the day. If your doctor has given you advice on your diet, you need to continue to follow this.
  • Do not drink large amounts of alcohol or take medicines containing alcohol while taking metformin

Pregnancy and breast-feeding

Do not take this medicine and talk to your doctor if you are pregnant, planning to get pregnant or are breast-feeding

Driving and using machines

  • Metformin on its own does not usually affect your ability to drive.
  • However, if you also take other medicines which lower blood sugar you may feel faint, dizzy, weak or shaky. If this happens, do not drive or use any tools or machines.

3. HOW TO TAKE METFORMIN

Always take metformin exactly as your doctor has told you. You should check with your doctor or pharmacist if you are not sure.

Taking this medicine

  • Swallow the tablets whole with a glass of water.
  • Do not crush or chew the tablets.
  • Take metformin with or after food. This lowers the chance of getting an upset stomach.
  • Try to take your medicine at the same time each day so that it becomes part of your daily routine.
  • Keep taking metformin until your doctor tells you to stop. Do not stop taking metformin just because you feel better. If you stop your illness may get worse.

How much to take

Adults

  • The usual starting dose is one tablet 2 or 3 times a day. Your doctor will tell you when to take this
  • After 10 to 15 days, your doctor may slowly increase your dose until the right dose for you is reached. This will help lower the chances of getting side effects such as feeling sick (nausea) or being sick (vomiting).
  • The maximum daily dose is six 500mg tablets or three 850mg tablets.

Elderly

  • Your doctor may give you a much lower starting dose as there is a risk of kidney problems.

Teenagers and children aged 10 years or older

  • The usual starting dose is one tablet each day. Your doctor will tell you when to take this
  • After 10 to 15 days, your doctor may slowly increase your dose until the right dose is reached. This will help lower the chances of getting side effects such as feeling sick (nausea) or being sick (vomiting).
  • The maximum daily dose is four 500mg tablets or two 850mg tablets.

Children aged under 10 years

Metformin is not recommended for use in children under 10 years old.

Taking metformin with insulin

  • If your doctor wants you to take metformin with insulin the usual starting dose of metformin is one tablet 2 or 3 times a day.
  • The insulin dose will change depending on your blood sugar level

If you take more metformin than you should

If you take too many tablets tell your doctor or go to the nearest hospital casualty department straight away. Remember to take the pack and any remaining tablets with you. This is so the doctor knows what you have taken.

The following effects may happen if you take too much metformin:

unexpected weight loss, feeling very sick or being very sick, very fast breathing which you cannot stop, stomach pains or feeling cold. You may have something called lactic acidosis. The doctor may use a method called ‘haemodialysis’ to remove the extra lactate and metformin from your body.

If you forget to take metformin

  • If you forget to take a dose, take it as soon as you remember, with your next meal. However, if it is time for your next dose, do not take the missed dose.
    Take only a single dose as usual.
  • Do not take a double dose to make up for a forgotten dose

If you stop taking metformin

Keep taking this medicine until your doctor tells you to stop

If you have any further questions on the use of this medicine, ask your doctor or pharmacist.

4. POSSIBLE SIDE EFFECTS

Like all medicines metformin can cause side effects, although not everybody gets them.

Stop taking metformin and see a doctor or go to a hospital straight away if you get any of the following very rare side effects:

  • unexpected weight loss
  • feeling very sick (nausea) or being very sick (vomiting)
  • very fast breathing which you cannot stop
  • stomach pains or feeling cold

This may mean you have something called “diabetic ketoacidosis” or “lactic acidosis”. These can be signs of serious problems with your diabetes. If this happens, see a doctor as you will need treatment straight away.

Other side effects:

Very common (affects more than 1 in 10 people)

  • Stomach problems such as feeling sick (nausea), being sick (vomiting), diarrhoea, stomach pain and loss of appetite. These side effects are most likely to happen at the start of treatment.
  • They usually last for a short time. It helps to take the dose with or after a meal.

Common (affects less than 1 in 10 people)

  • taste of metal in your mouth

Very rare (affects less than 1 in 10,000 people)

  • skin rash (including redness, itching, hives).
  • low levels of vitamin B12. Over time this may lead to anaemia, a sore mouth or tongue or possibly numbness or tingling in the limbs.
  • liver problems, abnormal liver function tests and hepatitis (inflammation of the liver) that may result in jaundice. If you notice yellowing of the eyes/skin contact your doctor immediately.

If any of the side effects gets serious, or if you notice any side effects not listed in the leafelt, please tell your doctor or pharmacist.

5. HOW TO STORE METFORMIN

  • Keep your medicine in a safe place out of the reach and sight of children.
  • Do not store above 25°C. Store in the original package.
  • Do not take this medicine after the expiry date which is stated on the carton, after EXP.
  • Medicines should not be disposed of via waste water or household waste. Ask your pharmacist how to dispose of medicines no longer required. These measures will help to protect the environment.

6. FURTHER INFORMATION

What Metformin 500mg or 850mg Tablets contain

Each tablet contains 500mg or 850mg of metformin hydrochloride as the active ingredient.

Other ingredients are sodium starch glycollate, maize starch, povidone, colloidal anhydrous silica, magnesium stearate, methylhydroxypropylcellulose, titanium dioxide (E171), propylene glycol, Macrogol 6000 and purified talc.

What Metformin 500mg or 850mg Tablets look like and contents of the pack

Metformin 500mg Tablets are white, biconvex, round, film-coated tablets. They are marked S137 on one side.

Metformin 850mg Tablets are white, biconvex, round, film-coated tablets. They are marked S138 on one side.

Metformin 500mg Tablets are available in blister packs of 28, 84, 300 and 500 tablets.

Metformin 800mg Tablets are available in blister packs of 28, 84, 300 and 500 tablets.

(Not all pack sizes may be marketed.)

The Marketing Authorisation Holder is:

Winthrop Pharmaceuticals
PO Box 611
Guildford
Surrey
GU1 4YS
UK

The Manufacturer is:

Winthrop Pharmaceuticals UK Ltd.
One Onslow Street
Guildford
Surrey
GU1 4YS
UK

This leaflet was prepared in July 2009

‘Winthrop’ is a registered trademark. © 2009 Winthrop Pharmaceuticals.

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