Metformin 500mg, box of 28 tablets

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Metformin Tablets


Metformin is a medicine that is used to treat type 2 diabetes by helping to bring your blood sugar levels under control.

Metformin is prescribed when lifestyle changes like diet and exercise plans have not been effective in controlling your blood sugars.

Treatment for: Type 2 Diabetes
Type of drug: biguanide
Prescription or over-the-counter: Prescription-only medication 
Branded or generic: Generic
Active ingredient: metformin hydrochloride
Dosages available: 500mg
Time to start working: 48 hours - 3 months
Common side effects include: sore stomach, loss of appetite, diarrhoea , problems with digestion, nausea, being sick

Last reviewed: 23-07-2020 by Dr Simran Deo

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Metformin 500mg SR from £20.00
Metformin 500mg MR from £20.00
Metformin 850mg SR from £20.00

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About Metformin

Metformin is used to treat type 2 diabetes. 

It reduces the sugar levels in your blood, and can be taken in two forms:

  • A standard release pill which is often taken twice or three times a day 
  • A slow release pill, which is taken once a day and lowers blood sugars over a prolonged period of time

The drug is also used to treat PCOS (polycystic ovary syndrome) when prescribed by a specialist.

Metformin works by improving how you respond to the insulin your body creates naturally, and reduces the amount of glucose (sugar) your liver produces.

Metformin brings down your blood sugar by:

  • lowering glucose production in the liver
  • lowering blood sugar by increasing the body’s sensitivity to insulin
  • decreasing the amount of glucose in your body both before and after eating

People with diabetes have poorly controlled blood sugar levels, which is often higher than normal. If you have type 2 diabetes, your body will not produce enough insulin, which is a hormone that balances the level of sugar in your blood

How long does Metformin take to work?

Metformin is a fast acting treatment for diabetes, and can help to effectively lower your blood sugar level in just 48 hours. It can take up to 3 months for your blood sugar levels to lower permanently while taking metformin.

What is the difference between Metformin standard release and Metformin modified release?

Modified-release is a type of pill that delivers a drug with a delay after its administration. This means that after taking the medication its effects will not be felt immediately. 

Modified release Metformin has the advantage of only being needed once a day and patients usually also experience fewer side effects.

Your doctor may prescribe slow release tablets if you have side effects such as diarrhoea when taking  standard release pills. 

Studies have shown better control of blood sugars with those taking slow release metformin compared to those taking the standard release. A study showed metformin and metformin slow release both improved blood sugar levels over 24 weeks in patients.

Metformin tablets should be swallowed whole with water, and should not be chewed. For best results you should take metformin with a meal, or shortly after it, to reduce the side effects.

The dosage you need will depend on a few factors, so you'll need to be assessed by a doctor to find the most suitable dosage for you.

Metformin is also available in a liquid form for people who find it difficult to take tablets. Superdrug Online Doctor does not currently offer liquid Metformin, so you'll need to speak to your GP if liquid metformin is a more suitable option for you.

You should take Metformin exactly as prescribed by your GP.

When is the best time of day to take Metformin?

Your doctor will tell you exactly when and how to take Metformin, however Metformin should be taken at the same times every day and during or after meals. 

What is the benefit of taking Metformin at night?

There is some evidence that it is better to take Metformin at night, just before bedtime, rather than in the evening. This is because the later timing may reduce hypoglycemia symptoms the next morning, however this should only be done on the advice of your doctor. 

What should I do if I forget to take a pill?

If you forget to take a dose of metformin, just take your next dose at the normal time. Do not take 2 tablets to make up for the dose you missed, as this may cause side effects.

How long can I take Metformin for?

You can take Metformin to treat diabetes for life, although many people can improve (and even reverse) their diabetes by making changes to their lifestyle, such as changing their diet and losing weight.

It is important to continue taking Metformin tablets until your doctor tells you to stop, and if you would like to stop taking Metformin then you should discuss it with a doctor first.

Your dosage of Metformin will depend on what your doctor decides is right for you, and depends on your blood sugars.  You should always take it exactly as prescribed.

The usual starting dose for adults is:

  • 500mg  taken once a day during or after meals

The maximum daily dose is 3000mg taken as 3 divided doses.

Factors such as your age, health and other prescribed medications will affect the dosage your doctor prescribes. If you have severe side effects, or problems with your kidneys, then your doctor may change your dosage. 

As with all medicines, you may suffer some side effects when taking Metformin, especially when you first start taking it. 

The most common side effects, which 1 in 10 people will experience, are:

  • sore stomach
  • loss of appetite
  • diarrhoea 
  • problems with digestion
  • nausea 
  • being sick

You may also notice a change in your sense of taste. Talk to your doctor or a pharmacist if you are worried about these side effects, or if they last longer than 1 week. 

If vomiting and diarrhoea are causing you to become dehydrated, you should contact your doctor.

Serious side effects of taking Metformin are:

  • yellow skin or the whites of your eyes turning yellow – these can be signs of liver problems
  • extreme tiredness, lack of energy, pins and needles, a sore and red tongue, mouth ulcers, muscle weakness and disturbed vision – these could be signs of vitamin B12 deficiency anaemia
  • a skin rash, redness or itching – this could be a sign of a skin disorder

If you have these symptoms you should contact your doctor.

If you have: 

  • swelling of your tongue, lips or face
  • shortness of breath
  • chest tightness or pain

then you may be having a severe allergic reaction called anaphylaxis. Stop taking Metformin and call 999 or go to A&E.

Who should not take Metformin?

Metformin is for adults and children over 10. Your doctor may not prescribe Metformin if you:

  • have severe and uncontrolled diabetes
  • have a history of allergic reactions to medicine
  • have problems with your kidney or liver
  • have serious heart problems
  • have problems with blood circulation and breathing
  • drink heavily

Are I more likely to experience side effects when taking Metformin for a long time?

If you take Metformin for a long time, you will need to go to the doctor for regular checks. Your doctor will check your blood glucose levels and make sure your dose of Metformin is correct. They will also check how well your kidneys are working at least once a year.

Will Metformin affect my sex drive?

There is no evidence that taking Metformin will affect your desire to have sex.

If you are taking any other drugs you should tell your doctor. This is because other medicines may affect how well Metformin works for you, which may influence the dose of Metformin the doctor gives you.

There is a full list of medicines which interact with Metformin here. These include:

  • other medicines used to treat diabetes
  • medicines for heart issues and high blood pressure
  • hormone tablets
  • steroids
  • diuretics – medicines which make you urinate

Is it safe to use contraceptives while on Metformin?

It is safe to use Metformin with contraception, though you should tell your doctor if you plan to start using the contraceptive pill. This is because the pill affects how your body deals with sugar, and so your doctor may need to adjust your Metformin dose.

Can I drink alcohol while on Metformin?

Drinking alcohol can increase your risk of low blood sugar, so we advise that you do not drink and take Metformin.

If you are pregnant or planning to become pregnant, then speak to your doctor about taking Metformin. Most women can continue to take the drug when pregnant, but your doctor may also prescribe insulin.

Can I take Metformin while breastfeeding?

This is considered to be safe, but speak to your doctor if you are taking Metformin and planning to breastfeed. The drug will be present in your breastmilk, but in such small quantities that it will not affect your baby.

Reviewed by: Dr Simran Deo in line with the Superdrug Online Editorial Process.

GMC no. 6141366

Dr Deo studied at St George’s, University of London and she has a special interest in dermatology.

Last reviewed on: 23/07/20