<p><strong>Blood and lymphatic system disorders</strong>: Not known: Hemolytic anemia<br />
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<strong>Metabolism and nutrition disorders</strong>: Very rare: Lactic acidosis. Decrease of vitamin B12 absorption with a decrease of serum levels during long-term use of metformin. Consideration of such etiology is recommended if a patient presents with megaloblastic anemia. Cases of peripheral neuropathy in patients with vitamin B12 deficiency have been reported in post-marketing experience (frequency not known)<br />
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<strong>Nervous system disorder</strong>s: Common: Taste disturbance. Not known: Encephalopathy<br />
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<strong>Gastrointestinal disorders</strong>: Very common: Gastrointestinal disorders, such as nausea, vomiting, diarrhea, abdominal pain, and loss of appetite. These undesirable effects occur most frequently during the initiation of therapy and resolve spontaneously in most cases. To prevent them, 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.<br />
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<strong>Hepatobiliary disorders</strong>: Very rare: Isolated reports of liver function test abnormalities or hepatitis resolving upon metformin discontinuation.<br />
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<strong>Skin and subcutaneous tissue disorders</strong>: Very rare: Skin reactions, such as erythema, pruritus, urticaria.</p>