Metformin: Uses, How It Works, Medicines
Also in: हिन्दी தமிழ் मराठी తెలుగు ಕನ್ನಡ বাংলা ગુજરાતી മലയാളം ਪੰਜਾਬੀ
Metformin is a medicine used to treat type 2 diabetes. It helps lower blood sugar by reducing the sugar the liver releases and helping the body respond better to its own insulin. In India it is a prescription medicine, used together with the diet and activity plan your doctor gives you.
Also known as: Metformin hydrochloride, Metformin 500 mg, Metformin IP, Metformin tablet, Biguanide, Diabetes tablet
Pharmacist review in progress. This page is based on the sources listed below and is being checked by our registered pharmacist.
How does Metformin work?
Metformin lowers the amount of sugar the liver releases, slows the amount of sugar absorbed from food in the gut, and makes muscles and other tissues respond better to insulin. It leaves the body mostly unchanged through the kidneys.
How to take Metformin
Follow the label or your doctor's advice. Metformin is usually taken with or just after meals, and the dose is set by your doctor and may be raised slowly. Do not stop it without talking to your doctor, because your blood sugar may rise again.
Side effects of Metformin
Most people take metformin without serious problems. Stomach and gut side effects are the most common, and they usually ease after the first couple of weeks.
Uncommon or mild
- Feeling sick (nausea) or being sick (vomiting)
- Diarrhoea
- Stomach pain
- Loss of appetite
- A change in how food tastes (often a metallic taste)
- Wind (gas) or indigestion
- Low vitamin B12 with long-term use, which can cause tiredness
Rare but serious: get medical help
- Signs of lactic acidosis (too much acid in the blood), a rare but serious problem: repeated vomiting, stomach pain, muscle cramps, fast or difficult breathing, feeling very tired or unwell. Get emergency medical help straight away
- Signs of a severe allergic reaction: swelling of the face, lips, tongue or throat, an itchy rash, or difficulty breathing
- Yellowing of the skin or eyes, dark urine or stomach pain that gets worse, which can be signs of liver problems
- Low blood sugar (shaking, sweating, hunger, confusion) if metformin is taken together with insulin or tablets such as sulfonylureas
Who should be careful
Metformin is removed from the body by the kidneys, so kidney health matters. Some situations raise the rare risk of lactic acidosis, so tell every doctor, dentist and hospital that you take it.
When the label says not to use it
- Allergy to metformin or any ingredient of the tablet
- Severe kidney problems
- Acid in the blood from diabetes (diabetic ketoacidosis) or other metabolic acidosis
- Heavy alcohol use, or a serious infection, unless your doctor decides otherwise
- Kidney problems: metformin may be unsuitable, and your doctor checks kidney function (eGFR) before you start and at least once a year. Tell your doctor about any kidney disease or if you are passing much less urine
- Liver disease, heart failure, lung disease or any serious infection: these raise the risk of lactic acidosis, so ask your doctor first
- Alcohol: heavy drinking and binge drinking raise the risk of lactic acidosis. Limit alcohol as your doctor advises
- Vomiting, diarrhoea or fever that causes dehydration: contact a doctor or pharmacist for advice, because metformin may need to be paused. Do not stop on your own unless told to
- Scans or X-rays that use an iodine-containing contrast dye, and surgery or procedures where you cannot eat or drink: tell the staff you take metformin, because it may need to be paused for a short time and kidney function rechecked afterwards
- Long-term use: it can lower vitamin B12, so your doctor may check blood tests from time to time
- Taking it with insulin or other diabetes tablets: low blood sugar becomes more likely, so know the warning signs
- Pregnancy or breastfeeding: poorly controlled diabetes carries risks, and metformin is sometimes used in pregnancy, but only on a doctor's advice. Only tiny amounts pass into breast milk
- Past allergic reaction to metformin
Medicines and things that interact with Metformin
Some medicines raise the chance of lactic acidosis or change blood sugar when taken with metformin. Tell your doctor or pharmacist about everything you take, including herbal remedies.
- Water tablets (diuretics), NSAID painkillers such as ibuprofen and diclofenac, and some blood pressure medicines: these can affect the kidneys or fluid balance, so they may not mix well with metformin
- Topiramate, zonisamide and acetazolamide (carbonic anhydrase inhibitors): they may raise the risk of lactic acidosis
- Cimetidine, dolutegravir, ranolazine and vandetanib: they can raise metformin levels in the body
- Insulin and sulfonylurea diabetes tablets: metformin on top of these can cause low blood sugar, so their doses sometimes need to be lowered
- Steroids (corticosteroids), thiazide water tablets and oestrogens: these can raise blood sugar, so your blood sugar may need closer checking
- Alcohol: it increases the effect of metformin on lactate and the risk of lactic acidosis
Effects on lab tests
- Kidney function (eGFR) test: checked before starting and at least yearly
- Vitamin B12 blood test: long-term use can lower B12
- Blood sugar and HbA1c tests: used to check how well the diabetes is controlled
If someone takes too much
Taking much more metformin than prescribed can cause lactic acidosis, which is a medical emergency. If someone has taken too much, or feels very unwell, sick, short of breath or has stomach pain after taking it, call 112 or go to the nearest hospital and take the medicine pack with you.
Regulatory status in India
Approved for sale in India as a prescription medicine. Single-ingredient metformin is not on the CDSCO list of banned medicines, but several fixed-dose combinations that include metformin have been prohibited under section 26A, so check the ingredient list on the pack.
Type of medicine
Metformin belongs to this type of medicine.
Medicines that contain Metformin
These medicines sold in India contain Metformin. They are listed A to Z, not ranked.
- Glycomet-500 · 500 mg tablet
What is Metformin used for?
Medicines that contain Metformin are used for these conditions.
Common questions
Is Glycomet-500 the same as metformin?
Glycomet-500 is a brand name for a tablet that contains 500 mg of metformin and nothing else. Other brands and generic tablets contain the same medicine. Some products in the same brand family add other ingredients, so check the ingredients and strength on the pack.
Is metformin a medicine for sugar (diabetes)?
Yes. Metformin is used to treat type 2 diabetes by helping to lower blood sugar, alongside diet and activity. It is a prescription medicine, so do not start, stop or change it without your doctor's advice.
Why does metformin cause loose stools or nausea?
Stomach and gut effects are the most common side effects and they usually ease after a couple of weeks. Taking the tablet with food may help. Tell your doctor if they do not settle or you cannot keep fluids down.
Can I take metformin if I have kidney problems?
Metformin is removed by the kidneys, so it may not be suitable if they do not work well. Your doctor checks kidney function before you start and at least yearly. Tell your doctor about any kidney disease, and do not change the dose yourself.
What is lactic acidosis?
Lactic acidosis is a build-up of acid in the blood. It is rare with metformin, but serious. Warning signs are repeated vomiting, stomach pain, muscle cramps, fast breathing and severe tiredness. Get emergency medical help straight away.
Can I drink alcohol while taking metformin?
Alcohol raises the risk of lactic acidosis, and heavy drinking can make metformin unsuitable. Limit how much you drink and ask your doctor what is right for you.
Do I need to stop metformin before a scan or surgery?
Sometimes. It may need to be paused for a short time around scans that use iodine contrast dye and around surgery, and kidney function is rechecked afterwards. Tell the hospital staff you take it and follow their instructions.
Can metformin cause vitamin B12 deficiency?
Yes. Long-term use can lower vitamin B12, which may cause tiredness or tingling in the hands and feet. Your doctor may check your blood from time to time. Do not start supplements or stop metformin without asking your doctor.
Sources
- Metformin: a medicine for type 2 diabetes. NHS (UK)
- Who can and cannot take metformin. NHS (UK)
- Side effects of metformin. NHS (UK)
- Type 2 diabetes: treatment. NHS (UK)
- Metformin hydrochloride tablets: prescribing information (label revised 7/2025, repackager copy). DailyMed, US National Library of Medicine
- Metformin. StatPearls, NCBI, US National Library of Medicine
- Metformin-Associated Lactic Acidosis (MALA). StatPearls, NCBI, US National Library of Medicine
- National Formulary of India. Indian Pharmacopoeia Commission
- List of drugs prohibited for manufacture and sale through gazette notifications under section 26A of the Drugs & Cosmetics Act 1940. Central Drugs Standard Control Organisation (CDSCO)
- National List of Essential Medicines 2022. Ministry of Health and Family Welfare, Government of India (copy hosted by CDSCO)