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Metformin Hydrochloride Brown & Burk 500 mg prolonged-release tablets – patient leaflet, side effects, dosage

Last updated: · Text from the MHRA, as of · About this document

Medicine status: Prescription only (POM) Details

Medicine strength:
500 mg
Contains active substance:
ATC code:

Patient leaflet - Metformin Hydrochloride Brown & Burk 500 mg prolonged-release tablets

1. What Metformin Hydrochloride Prolonged-release Tablets is and what it is used for

at risk for lactic acidosis (see 'Warnings and precautions'). • you are a heavy drinker of alcohol.

  • you are under 18 years of age.

Warnings and precautions:

Risk of lactic Acidosis

Metformin Hydrochloride Prolonged-release Tablets may cause a very rare, but very serious side effect called lactic acidosis, particularly if your kidneys are not working properly. The risk of developing lactic acidosis is also increased with uncontrolled diabetes, serious infections, prolonged fasting or alcohol intake, dehydration (see further information below), liver problems and medical conditions in which a part of the body has a reduced supply of oxygen (such as acute severe heart disease).

If any of the above apply to you, talk to your doctor for further instructions.

Talk to your doctor promptly for further instructions if:

  • You are known to suffer from a genetically inherited disease

    affecting mitochondria (the energy-producing components within cells) such as MELAS syndrome (Mitochondrial Encephalopathy, myopathy, Lactic acidosis and Stroke-like episodes) or Maternal inherited diabetes and deafness (MIDD).

Metformin Hydrochloride Prolonged-release Tablets contain the active ingredient metformin hydrochloride and belong to a group of medicines called biguanides. Metformin hydrochloride is used for the treatment of "Type 2 diabetes" (non-insulin dependent diabetes) diabetes mellitus.

  • You have any of these symptoms after starting metformin:

    seizure, declined cognitive abilities, difficulty with body movements, symptoms indicating nerve damage (e.g. pain or numbness), migraine and deafness.

Metformin Hydrochloride Prolonged-release Tablets are used together with the diet and exercise to lower the risk of developing Type-2 diabetes in overweight adults, when diet and exercise alone for 3 to 6 months have not been enough to control blood glucose level (sugar). You are at high risk of developing Type 2 diabetes if you have additional conditions like high blood pressure, age above 40 years, an abnormal amount of lipids (fat) in the blood or a history of diabetes during the pregnancy.

The medicine is particularly effective if you are aged below 45 years, are very overweight, have high blood glucose levels after a meal or developed diabetes during pregnancy.

Stop taking Metformin Hydrochloride Prolonged-release Tablets for a short time if you have a condition that may be associated with dehydration (significant loss of body fluids) such as severe vomiting, diarrhoea, fever, exposure to heat or if you drink less fluids than normal. Talk to your doctor for further instructions.

Stop taking Metformin Hydrochloride Prolonged-release Tablets and contact a doctor or the nearest hospital immediately if you experience some of the symptoms of lactic acidosis, as this conditions may lead to coma.

Metformin Hydrochloride Prolonged-release Tablets are used for the treatment of Type 2 diabetes when diet and exercise changes alone have not been enough to control your blood glucose (sugar). 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. People with Type 2 diabetes do not make enough insulin in their pancreas or their body does not respond properly to the insulin it does make. This causes a build-up of glucose in the blood which can cause a number of serious long-term problems so it is important that you continue to take your medicine, even though you may not have any obvious symptoms. Metformin Hydrochloride Prolonged-release Tablets make the body more sensitive to insulin and helps return to normal the way your body uses glucose.

Metformin Hydrochloride Prolonged-release Tablets are associated with either a stable body weight or modest weight loss.

Metformin Hydrochloride Prolonged-release Tablets are specially made to release the drug slowly in your body and therefore are different to many other types of tablets containing metformin.

Symptoms of lactic acidosis includes:

  • vomiting
  • stomach ache (abdominal pain)
  • muscle cramps
  • a general feeling of not being well with severe tiredness • difficulty in breathing
  • reduced body temperature and heartbeat

Lactic acidosis is a medical emergency and must be treated in a hospital.

If you need to have major surgery you must stop taking Metformin Hydrochloride Prolonged- release Tablets during and for some time after the procedure. Your doctor will decide when you must stop and when to restart your treatment with Metformin Hydrochloride Prolonged- release Tablets.

During treatment with Metformin Hydrochloride Prolonged-release Tablets, your doctor will check your kidney function at least once a year or more frequently if you are elderly and/or if you have worsening kidney function.

Polycystic ovary syndrome (PCOS) is a health condition that affects a woman's hormone levels, menstrual cycle, and ability to have children. Metformin Prolonged-release Tablets is used in women with PCOS to stimulate ovulation (release of an egg from the ovaries), and subsequently the chance of getting pregnant, alone or together with other treatment options.

If you are older than 75 years, treatment with Metformin Hydrochloride Prolonged-release Tablets should not be started to lower the risk of developing type 2 diabetes.

You may see some remains of the tablets in your stools. Do not worry- this is normal for this type of tablet.

2. What you need to know before you take Metformin Hydrochloride Prolonged-release Tablets

You should continue to follow any dietary advice that your doctor has given you and you should make sure that you eat carbohydrates regularly throughout the day.

Do not take Metformin Hydrochloride Prolonged-release Tablets if:

  • you are allergic to Metformin Hydrochloride Prolonged-release

    Tablets or to any other ingredients of this medicine (listed in section 6). An allergic reaction may cause a rash, itching or shortness of breath.

  • you have liver problems
  • you have uncontrolled diabetes, with, for example, severe

    hyperglycaemia (high blood glucose), nausea, vomiting, diarrhoea, rapid weight loss, lactic acidosis (see 'Risk of lactic acidosis' below) or ketoacidosis. Ketoacidosis is a condition in which substances called 'ketone bodies' accumulate in the blood and which can lead to diabetic pre-coma. Symptoms include stomach pain, fast and deep breathing, sleepiness or your breath developing an unusual, fruity smell. • you have been treated for acute heart problems or have

    recently had a heart attack or you have severe circulation problems or breathing difficulties. This may lead to a lack in oxygen supply to tissue which can put you at risk for lactic acidosis (see 'Warnings and precautions').

  • You have a severe infection, such as an infection affecting your

    lung or bronchial system or your kidney. Severe infections may lead to the kidney problems, which can put you at risk for lactic acidosis (see 'Warnings and precautions').

  • you have severely reduced kidney function
  • you have lost too much of water from your body (dehydration).

    Dehydration may lead to kidney problems, which can put you

    Do not stop taking this medicines without speaking to your doctor.

    Other medicines and Metformin Hydrochloride Prolonged-release Tablets

    If you need to have an injection of a contrast medium that contains iodine into your bloodstream, in the context of an X-ray or scan, you must stop taking Metformin Hydrochloride Prolonged-release Tablets before or at the time of injection. Your doctor will decide when you must stop and when to restart your treatment with Metformin Hydrochloride Prolonged-release Tablets.

    Tell your doctor or pharmacist if you are taking or have recently taken any other medicines. You may need more frequent blood glucose and kidney function tests, or your doctor may need to adjust the dosage of Metformin Hydrochloride Prolonged-release Tablets. It is especially important to mention the following: • Steroids such as prednisolone, mometasone, beclometasone. • Medicines which increases urine production (diuretics (water

    tablets) such as furosemide).

    • Certain medicines for the treatment of high blood pressure

      (ACE-inhibitors and angiotensin II

      receptor antagonists).

    • Medicines used to treat pain and

      inflammation (NSAID and COX-2

      inhibitors, such as ibuprofen and

      celecoxib).

      • Sympathomimetic medicines including epinephrine and

        dopamine used to treat heart attacks and low blood pressure. Epinephrine is also included in some dental anaesthetics. • Medicines that may changes the amount of Metformin

        Hydrochloride Prolonged-release Tablets in your blood, especially if you have reduced kidney function (such as verapamil, rifampicin, cimetidine, dolutegravir, ranolazine, trimethoprim, vandetanib, isavuconazole, crizotinib, olaparib)

Metformin Hydrochloride Prolonged-release Tablets with alcohol

Avoid excessive intake of alcohol while taking Metformin Hydrochloride Prolonged-release Tablets since this may increase the risk of lactic acidosis (see section 'Warnings and precautions').

Pregnancy and breast-feeding

If you are pregnant think you may be pregnant or are planning to have a baby, speak your doctor in case any changes will be needed to your treatment or monitoring of your blood glucose levels

This medicine is not recommended if you are breast-feeding or if you are planning to breast-feed your baby.

Women of childbearing potential

Metformin Prolonged-release Tablets can stimulate ovulation (release of an egg from the ovaries), in women who do not ovulate properly. Beware of an increased chance of becoming pregnant when using Metformin Prolonged-release Tablets.

Driving and using machines

Metformin Hydrochloride Prolonged-release Tablets taken on its own does not cause 'hypos' (symptoms of low blood sugar or hypoglycaemia, such as faintness, confusion and increased sweating) and therefore should not affect your ability to drive or use machinery.

You should be aware, however, that Metformin Hydrochloride Prolonged-release Tablets taken with other antidiabetic medicines can cause hypos, so in this case you should take extra care when driving or operating machinery.

Metformin Hydrochloride Brown & Burk contains sodium

This medicine contains less than 1 mmol sodium (23 mg) per prolonged-release tablet, that is to say essentially ‘sodium free’.

3. How to take Metformin Hydrochloride Prolonged-release Tablets

Your doctor may prescribe Metformin Hydrochloride Prolonged-release Tablets for you to take on its own, or in combination with other oral antidiabetic medicines or insulin.

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

Swallow the tablets whole with a glass of water, do not chew.

Recommended dose:

Usually you need to start treatment with 500 milligrams Metformin Hydrochloride Prolonged-release Tablets daily. After you have been taking Metformin Hydrochloride Prolonged-release Tablets for about 2 weeks, your doctor may measure your blood sugar and adjust the dose. The maximum daily dose is 2000 milligram of Metformin Hydrochloride Prolonged-release Tablets.

If you have reduced kidney function, your doctor may prescribe a lower dose.

Normally, you should take the tablets once a day, with your evening meal.

In some cases, your doctor may recommend that you take the tablets twice a day. Always take the tables with food.

Polycystic ovary syndrome (PCOS)

The usual dose is 1500-2000 mg metformin hydrochloride taken once a day with the evening meal. You should check with your doctor or pharmacist when to stop taking the medicine.

If you take more Metformin Hydrochloride Prolonged-release Tablets than you should

If you take extra tablets by mistake you need not worry, but if your unusual symptoms, contact your doctor. If the overdose is large, lactic acidosis is more likely. Symptoms of lactic acidosis are non-specific, such as vomiting, bellyache with muscle cramps, a general feeling of not being well with severe tiredness, and difficulty in breathing. Further symptoms are reduced body temperature and heartbeat. If you experience some of these symptoms, you should immediately seek medical attention, as lactic acidosis may lead to coma. Stop taking Metformin Hydrochloride Prolonged-release Tablets immediately and contact a doctor or the nearest hospital straightaway.

If you forget to take Metformin Hydrochloride Prolonged-release Tablets

Take it as soon as you remember with some food. Do not take a double dose to make up for a forgotten dose.

4. Possible side effects

Like all medicines, Metformin Hydrochloride Prolonged-release Tablets can cause side effects, although not everybody gets them. The following side effects may occur:

Metformin Hydrochloride Prolonged-release Tablets may cause a very rare (may affect up to 1 in 10,000 people) but very serious side effect called lactic acidosis (see section 'Warnings and precautions'). If this happens, you must stop taking Metformin Hydrochloride Prolonged-release Tablets and contact a doctor or the nearest hospital immediately, as lactic acidosis may lead to coma.

Metformin Hydrochloride Prolonged-release Tablets may cause abnormal liver function tests and hepatitis (inflammation of the liver) which may result in jaundice (may affect up to 1 in 10,000 people). If you develop yellowing of the eye and/or skin contact your doctor immediately.

If you get these, do not stop taking the tablet as these symptoms will normally go away in about 2 weeks. It helps if you take the tablets with or immediately after a meal.

Common (may affect up to 1 in 10 people):

  • Taste disturbance
  • Decreased or low vitamin B12 levels in the blood (symptoms may include extreme tiredness (fatigue), a sore and red tongue (glossitis), pins and needles (paraesthesia) or pale or yellow skin). Your doctor may arrange some tests to find out the cause of your symptoms because some of these may also be caused by diabetes or due to other unrelated health problems.

Very rare (may affect up to 1 in 10,000 people):

  • Skin rashes including redness, itching and hives.

Reporting of side effects

If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme. Website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.

By reporting side effects you can help provide more information on the safety of this medicine.

5. How to store Metformin Hydrochloride Prolonged-release Tablets

Keep this medicine out of the sight and reach of children.

Do not use them after the expiry date that is printed on the pack after “EXP:”. The expiry date refers to the last day of that month.

This medicinal product does not require any special storage conditions.

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. Contents of the pack and other information

What Metformin Hydrochloride

Prolonged-release Tablets contain

The active substance is metformin

hydrochloride.

500 mg: Each Prolonged-release

Tablets contains 500 mg metformin

hydrochloride equivalent to 390 mg

metformin base.

750 mg: Each Prolonged-release

Tablets contains 750 mg metformin

hydrochloride equivalent to 585 mg metformin base.

1000 mg: Each Prolonged-release Tablets contains 1000 mg metformin hydrochloride equivalent to 780 mg metformin base.

The other ingredients are Povidone K-90F, Colloidal anhydrous silica, Carmellose sodium, Hypromellose 90SH, Microcrystalline Cellulose, Magnesium Stearate.

What Metformin Hydrochloride Prolonged-release Tablets look like and contents of the pack

500 mg: White to off white, round shaped, biconvex tablets, debossed on one side with “500” and other side plain with approximately 12.15 mm diameter.

750 mg: White to off white, capsule shaped, biconvex tablets, debossed on one side with '750' and on the other side plain. The tablets are approximately 20.0 mm in length and 9.6 mm in breadth.

1000 mg: White to off white, capsule shaped, biconvex tablets, debossed on one side with '1000' and on the other side plain. The tablets are approximately 22.6 mm in length and 10.6 mm in breadth.

The tablets are available in blister strips [Clear PVC Film, coated with PVdC and Aluminium Foil].

Pack size:

500mg:

20, 28, 30, 50, 56, 60, 84, 90, 100, 112, 120, 180, 600 tablets in blister.

750 mg:

14, 20, 28, 30, 50, 56, 60, 84, 90, 100, 112, 120, 180 or 600 tablets in blister.

1000 mg:

14, 20, 28, 30, 50, 56, 60, 84, 90, 100, 112, 120, 180 or 600 tablets in blister.

Not all pack sizes may be marketed.

Marketing Authorisation Holder and Manufacturer

Brown & Burk UK Limited

5 Marryat Close

Hounslow

TW4 5DQ

United Kingdom.

This leaflet was last revised in 03/2025.

BBUKCODE

170 mm

About this document

Source: MHRA - Medicines and Healthcare products Regulatory Agency (products.mhra.gov.uk) · Marketing authorisation: PL 25298/0227

Last revision stated in the text: March 2025 · MHRA data as of 13 October 2026

Found a mistake? Tell us on the contact page.

The information on this site does not replace the advice of a doctor or pharmacist.

Facts about Metformin Hydrochloride Brown & Burk 500 mg prolonged-release tablets

Prescription needed? Yes, prescription-only medicine (POM)
Active substance Metformin
Strength 500 mg
Pharmaceutical form Modified-release tablet
How is it taken Oral
Pack sizes 28 tablet, 56 tablet
Is it available? Listed as available (NHS Dictionary of Medicines and Devices – not a record of current supplies)
Drug group (ATC)
  1. A Alimentary tract and metabolism drugs
    1. A10 Drugs used in diabetes
      1. A10B Blood glucose lowering drugs, excl. insulins
        1. A10BA Biguanide blood glucose lower drugs
          1. A10BA02 metformin
Marketing authorisation PL 25298/0227
Codes GTIN 5060124641935, 5060124641942 · BNF 06010202

Sources: the MHRA product information (products.mhra.gov.uk) and the NHS Dictionary of Medicines and Devices (dm+d), release 10.2.0 of 19 October 2026, NHS Business Services Authority. Contains public sector information licensed under the Open Government Licence v3.0.