Similarly to all medicines, Metformin might cause side effects.
Gastrointestinal symptoms such as nausea, vomiting, diarrhoea, abdominal pain and loss of appetite are very common: these occur most frequently during initiation of therapy and resolve spontaneously in most cases. To prevent these gastrointestinal symptoms, it is recommended that metformin be taken in 2 or 3 daily doses during or after meals. A slow increase of the dose may also improve gastrointestinal tolerability.
Metallic taste is common. Mild erythema is very rare.
A decrease of vitamin B12 absorption with decrease of serum levels has been observed in patients treated long- term with metformin and appears generally to be without clinical significance.
Lactic acidosis is very rare.
If any of the previously mentioned side effects are trouble some, severe, or do not wear off as treatment goes on tell a doctor. If the patient have any other side effects not listed in this patient information leaflet, notify a doctor or pharmacist.