What metformin is used for
Metformin is a prescription medicine used to control blood sugar in type 2 diabetes. It is usually the first medicine doctors choose, along with diet changes and exercise. Doctors also sometimes prescribe it for prediabetes in people at high risk, and for polycystic ovary syndrome (PCOS), where it can help with insulin resistance.
Type 2 diabetes is very common in India, including in younger adults and people who are not visibly overweight. Keeping sugar under control with medicines like metformin reduces the long-term risk of damage to the eyes, kidneys, nerves, heart and feet.
- Type 2 diabetes, alone or with other diabetes medicines
- Prediabetes in selected high-risk people
- Polycystic ovary syndrome (PCOS), on a doctor's advice
How metformin works
In type 2 diabetes, the liver releases too much sugar into the blood and the body's cells do not respond well to insulin. Metformin mainly reduces the amount of sugar the liver makes, and it helps muscles use insulin better. It also slightly reduces sugar absorption from the gut.
Because metformin does not push the pancreas to release more insulin, it rarely causes low blood sugar when used alone. It is also weight-neutral and may help with modest weight loss. Doctors often combine it with other diabetes medicines when one medicine is not enough, but that is always the doctor's decision.
Metformin side effects: common and serious
The most common side effects affect the stomach: nausea, loose stools, bloating, stomach discomfort, a metallic taste and reduced appetite. These are often worst when starting and usually settle over a few weeks. Doctors often start with a small amount and increase slowly, and extended-release forms can be gentler.
Long-term use can lower vitamin B12 levels, which may cause tiredness, anaemia or tingling and numbness in the feet. A rare but serious side effect is lactic acidosis, a build-up of acid in the blood, mostly in people with severe kidney disease, liver failure, heavy alcohol use or serious illness with dehydration.
Who should take extra care with metformin
Metformin may need to be reduced or stopped by your doctor if kidney function is poor, so kidney tests are done before starting and regularly afterwards. People with liver disease, heart failure, heavy alcohol use or frequent severe illness need careful assessment. Elderly people need regular kidney checks.
Metformin is only on a doctor's prescription, and you should not start or stop it on your own. In pregnancy, doctors sometimes use metformin, but insulin is often preferred, so tell your doctor if you are pregnant or planning pregnancy. It is used in children with type 2 diabetes only under specialist care.
Metformin interactions to know
Iodine-based contrast dyes used in some CT scans and X-ray procedures can affect the kidneys. Your doctor may ask you to pause metformin around such tests; always tell the radiology team you take it. Doctors may also pause it before major surgery or during a severe illness with vomiting, diarrhoea or dehydration.
Alcohol, especially heavy drinking, increases the risk of lactic acidosis and low sugar. Some medicines, such as certain water tablets, steroids and some antibiotics or antacids, can affect sugar levels or metformin levels. Tell every doctor and pharmacist that you take metformin.
Practical tips for using metformin
Take metformin exactly as your doctor prescribes, usually with or after meals to reduce stomach upset. Do not skip meals. Keep regular follow-up appointments and have your HbA1c, kidney function and vitamin B12 checked as your doctor advises. Keep a simple diary of your sugar readings to show at each visit.
Medicine works best with healthy habits. Eat regular meals with more vegetables, dal and whole grains and smaller portions of rice or chapati, cut down on sweets, sweetened tea and fried snacks, walk daily and keep a healthy weight. If you have a stomach bug with vomiting or diarrhoea, ask your doctor whether to pause metformin until you can eat and drink normally.
When to talk to your doctor about metformin
See your doctor if stomach side effects do not settle, if you notice tingling or numbness in your feet, or if your sugar readings stay high. Seek urgent care for severe weakness, fast breathing, severe belly pain or unusual drowsiness. Always talk to your doctor or pharmacist before changing how you take metformin.
Related medicines
Only your doctor can decide which medicine, dose and combination is right for you.
- Sulfonylureas such as glimepirideHelp the pancreas release more insulin.Only on a doctor's prescription; can cause low blood sugar.
- DPP-4 inhibitors such as sitagliptin or teneligliptinHelp the body release insulin after meals.Only on a doctor's prescription.
- SGLT2 inhibitors such as dapagliflozin or empagliflozinRemove extra sugar through the urine.Only on a doctor's prescription; keep well hydrated and watch for genital infections.
- InsulinReplaces or adds to the body's own insulin.Only on a doctor's prescription; needs training and sugar monitoring.
See a doctor urgently if
- Fast or deep breathing, severe weakness or muscle pain with a feeling of being very unwell
- Severe vomiting or diarrhoea so you cannot keep fluids down
- Unusual drowsiness or confusion
- Blood sugar readings that stay very high despite treatment
- Tingling, burning or numbness in the feet or hands
Tests that may help
This article is general health information, not medical advice. Do not start, stop or combine medicines on your own — always follow your doctor's prescription and ask your pharmacist if unsure.