Metformin

Metformin is a prescription medicine mainly used to treat type 2 diabetes. It is generally well tolerated by many people but can cause stomach upset, and it carries a rare but serious risk of lactic acidosis. This article explains how it is used, its risks, and its listed price in India.

Metformin at a Glance

What Is Metformin?

Metformin is a biguanide used to treat type 2 diabetes, alone or with other diabetes medicines, including insulin. It helps lower blood sugar by improving the body’s response to insulin, and it works best with diet and exercise.

Type 1 diabetes: metformin is mainly for type 2 diabetes. The US prescribing information approves it for type 2 diabetes and its patient leaflet says it is not for people with type 1 diabetes or diabetic ketoacidosis. The NHS notes that metformin is sometimes used in type 1 diabetes, but only together with insulin. It never replaces insulin. Anyone with type 1 diabetes should use it only on specialist medical advice.

How Metformin Works

Metformin is an anti-hyperglycemic agent. It improves glucose tolerance in people with type 2 diabetes by lowering both fasting (basal) and after-meal (postprandial) blood sugar. It decreases glucose production by the liver, decreases glucose absorption and improves insulin sensitivity in muscle and fat cells. It does not increase insulin secretion, and fasting insulin levels and the day-long insulin response may decrease.

When Metformin Is Used

• Type 2 diabetes: to help control blood sugar in adults and, per the US label, in children aged 10 years and older.
• PCOS: the NHS lists metformin for symptoms of polyendocrine metabolic ovarian syndrome (PMOS), previously called polycystic ovary syndrome (PCOS). This is not an approved indication on the US label I reviewed. It is not automatically suitable for everyone with PCOS, and your doctor decides.

Metformin Dosage and How to Take It

Dose and form depend on your condition, kidney function, other medicines, the formulation and how you respond. Your doctor usually starts with a low dose and increases it gradually.

US immediate-release tablet information (not an instruction for any individual, and not an Indian label): the US label says adults start at 500 mg twice daily or 850 mg once daily with meals, increased gradually, up to a maximum of 2,550 mg per day in divided doses. For children aged 10 and older, it says to start at 500 mg twice daily with meals, up to a maximum of 2,000 mg per day. Prescribing in India may differ.

Extended-release and sustained-release tablets (for example Gluconorm SR) have different dosing and are usually taken once a day with the evening meal. Do not apply the immediate-release figures above to them.

Take this medicine only as advised by your doctor or healthcare professional. Do not start, stop, or change the dose on your own.

• Take regular tablets with meals.
• Swallow extended-release tablets whole.
• Metformin also comes as a liquid or powder. If you are prescribed one, follow the instructions on the product and from your doctor or pharmacist. This article does not give liquid dosing.
• If you miss a dose, take it when you remember, unless it is nearly time for the next one. Do not take two doses to make up for a missed dose.
• Illness: if you have a serious infection, severe vomiting or diarrhea, or are not drinking enough fluid, contact your doctor. You may be advised to pause metformin temporarily.

Surgery and contrast scans

Tell your doctor and the radiology or surgical team that you take metformin, and follow their instructions on when to stop and restart. Whether it is paused depends on the procedure, your kidney function and other risk factors, so not every scan requires stopping it. The US label says metformin should be discontinued at or before an iodinated contrast procedure in patients with eGFR 30–60, a history of liver disease, alcoholism or heart failure, or those receiving intra-arterial contrast, with kidney function re-checked 48 hours later. It also says metformin should be temporarily stopped while food and fluid intake are restricted (for example around surgery). Do not stop or restart it on your own.

Side Effects of Metformin

Common side effects (usually stomach-related)

• Diarrhea, nausea and vomiting, stomach discomfort, gas and indigestion
• Weakness or low energy, headache
• Taste changes (the NHS notes these often ease after a couple of weeks)

Rare but serious: lactic acidosis

Lactic acidosis is a rare but potentially life-threatening build-up of lactic acid. The US label’s boxed warning says it has resulted in death. Ordinary nausea or stomach upset alone does not mean you have it. Symptoms can start vaguely and may include

• Extreme tiredness, weakness or general feeling of being unwell
• Muscle pain or cramps
• Fast or difficult breathing
• Stomach pain, nausea or vomiting, loss of appetite
• Drowsiness, dizziness
• Abnormal heartbeat, low blood pressure
• Feeling cold, particularly in the hands and feet

If you suspect lactic acidosis, stop taking metformin and get urgent medical help immediately (call your local emergency number or go to the nearest emergency department). The label directs doctors to discontinue metformin immediately and give hospital care. Do not wait to see whether symptoms settle.

Other important effects

• Vitamin B12 deficiency, which can cause tiredness. Doctors may check blood counts and vitamin B12 levels periodically (the US label says annually for blood counts and every 2 to 3 years for B12). Do not diagnose or treat a deficiency yourself.
• Allergic reactions: metformin must not be used if you are allergic to it. The NHS lists anaphylaxis as a rare effect. Seek emergency help for swelling of the lips, face or throat or trouble breathing.
• Liver problems: liver injury has been reported rarely after approval. Contact your doctor about yellow skin or eyes, dark urine or severe stomach pain.
• Chest pain needs immediate medical attention (MedlinePlus).

Metformin Precautions and Warnings

Formal contraindications (US label)

• Severe kidney impairment (eGFR below 30 mL/min/1.73 m²).
• Known hypersensitivity (allergy) to metformin.
• Acute or chronic metabolic acidosis, including diabetic ketoacidosis.

Kidney function (US label)

Doctors assess kidney function before starting and periodically after. Starting is not recommended at an eGFR of 30–45. If eGFR falls below 45, the benefit and risk of continuing are reassessed, and metformin is discontinued if it falls below 30. These thresholds come from the US label. Indian labelling may differ.

Risk factors for lactic acidosis

These are listed in the US boxed warning. These are not all equally serious, and they do not automatically rule out metformin, but they need your doctor’s attention.

• Kidney impairment, and age 65 or over
• Liver disease. The label advises avoiding metformin if there is clinical or laboratory evidence of liver disease
• Excessive alcohol intake
• Low-oxygen states and conditions such as heart failure
• Iodinated contrast procedures and surgery
• Certain medicines (see interactions)
• Dehydration from severe vomiting or diarrhea (MedlinePlus advises contacting your doctor in this situation)

Low blood sugar

The risk is higher when metformin is combined with insulin or insulin secretagogues such as sulfonylureas. Your doctor may adjust those medicines. Do not change doses yourself.

Metformin Drug Interactions

These interactions differ in importance. Depending on the medicine and your situation, a healthcare professional may monitor you more closely, change a dose or avoid the combination.

• Carbonic anhydrase inhibitors (topiramate, zonisamide, acetazolamide, dichlorphenamide): may increase the risk of lactic acidosis. More frequent monitoring may be advised.
• Medicines that reduce metformin clearance (ranolazine, vandetanib, dolutegravir, cimetidine): may increase metformin levels. Your doctor weighs the benefits and risks.
• Alcohol: increases metformin’s effect on lactate metabolism.
• Insulin and insulin secretagogues (for example sulfonylureas): higher risk of low blood sugar.
• Medicines that affect blood sugar (for example thiazide diuretics, corticosteroids, estrogens and oral contraceptives): closer blood sugar monitoring may be needed when they are started or stopped.

This list is not complete. Tell your doctor or pharmacist about all prescription medicines, OTC medicines, supplements and herbal products you use.

Metformin in Pregnancy and Breastfeeding

Neither pregnancy nor breastfeeding is automatically safe or unsafe with metformin. Your doctor decides after an individual assessment.

• Pregnancy: the US label says the available data are not sufficient to determine a drug-associated risk for major birth defects or miscarriage, and notes that poorly controlled diabetes in pregnancy carries risks to mother and baby. The NHS says metformin can be taken in pregnancy but advises checking with a doctor first. Tell your doctor if you are pregnant or planning a pregnancy.
• Ovulation: the US label says metformin may result in ovulation in some women who do not ovulate regularly, so the possibility of unintended pregnancy should be discussed with premenopausal women.
• Breastfeeding: the US label says limited studies report that metformin is present in human milk, with infant doses estimated at about 0.11% to 1% of the mother’s weight-adjusted dose, and that the data are insufficient to determine effects on the baby. The NHS says metformin can usually be taken while breastfeeding because only tiny amounts pass into milk, but advises checking with a doctor first.

Metformin Brands, Strengths and Price in India

Prescription brands with Indian retail listings. Prices apply only to the exact brand, strength, form and pack shown. They do not apply to other metformin brands or strengths.

Listings were opened on 13 October 2026. Stock status was not shown on any of them. Prices and availability vary by retailer, location and date. This is not a recommendation to buy or use metformin without a prescription.

How HealthPil Can Help

Medicines should be started, adjusted, or stopped only under the guidance of a qualified healthcare professional. If you have questions about this medicine, its side effects, or your treatment plan, you can consult a doctor through HealthPil.