Glucophage (Metformin): Uses, Safety and Interactions

What this tablet contains

Glucophage 500 mg contains metformin hydrochloride in a conventional film-coated tablet. This page concerns the immediate-release product, not Glucophage SR or another extended-release formulation. The reviewed UK authorisation covers type 2 diabetes when diet and exercise are insufficient, in adults and children aged 10 years and older. It can be used alone or with other diabetes medicines according to the clinical situation. Formulations and national authorisations should not be treated as interchangeable instructions.

Stomach effects and vitamin B12

Nausea, diarrhoea, abdominal discomfort and loss of appetite are common early problems. Persistent symptoms deserve review rather than an unplanned change in treatment. Long-term metformin can reduce vitamin B12, particularly with higher exposure, longer use or other deficiency risks. New pins and needles, unusual tiredness, a sore red tongue or pallor may justify testing; these symptoms can also have other causes. UK safety advice recommends treating confirmed deficiency and considering periodic monitoring in people at risk, rather than automatically stopping tolerated metformin.

Lactic acidosis and kidney precautions

Metformin-associated lactic acidosis is rare but serious. Kidney impairment, dehydration, severe infection, oxygen shortage and excessive alcohol increase concern. Severe weakness, muscle pain, unusual drowsiness, abdominal symptoms or breathing difficulty require urgent assessment. Kidney function is checked before and during treatment. Tell the clinical team before surgery or imaging with iodinated contrast, because a temporary interruption and a kidney reassessment may be required. The timing depends on the procedure and local product information.

Interactions and reproductive considerations

NSAIDs, diuretics and other medicines affecting kidney function need careful review, particularly during illness or dehydration. Cimetidine, dolutegravir and certain other transporter-inhibiting medicines can increase metformin exposure. Insulin and sulfonylureas may add hypoglycaemia risk even though metformin alone usually does not cause it. The UK label permits consideration during pregnancy when clinically needed; breastfeeding advice differs across authorities and requires an individual discussion. This is a summary of cited UK information with supportive US metformin safety information, not a personal dose or switching plan.

Sources

• Glucophage 500 mg film-coated tablets — UK SmPC — Merck; text revision November 2025; emc updated 22 December 2025
• Metformin and reduced vitamin B12 levels — MHRA safety update — Medicines and Healthcare products Regulatory Agency; 20 June 2022
• Metformin hydrochloride immediate-release tablets — US prescribing information — NuCare repackaged label; source NDC 59651-856; DailyMed updated 26 October 2026

Source check: 30 October 2026. This records a source check, not a clinical review by a doctor or pharmacist. Follow the current leaflet supplied with your medicine and seek professional advice for personal treatment.