The following adverse effects may occur under treatment with Metformin. Frequencies are defined as follows: very common: ≥1/10; common ≥1/100, <1/10; uncommon ≥1/1,000, <1/100; rare ≥1/10,000, <1/1,000; very rare <1/10,000.
Metabolism and Nutrition Disorders: Very rare: Lactic acidosis (see Precautions), Decrease of vitamin B12 absorption with decrease of serum levels during long-term use of Metformin. Consideration of such aetiology is recommended if a patient presents with megaloblastic anaemia.
Nervous System Disorders: Common: Taste disturbance.
Gastrointestinal Disorders: Very common: Gastrointestinal disorders such as nausea, vomiting, diarrhoea, abdominal pain and loss of appetite. These undesirable effects occur most frequently during initiation of therapy and resolve spontaneously in most cases. A slow increase of the dose may also improve gastrointestinal tolerability.
Hepatobiliary Disorders: Very rare: Liver function tests abnormalities or hepatitis resolving upon Metformin discontinuation.
Skin and Subcutaneous Tissue Disorders: Very rare: Skin reactions such as erythema, pruritus, urticaria.