Millions of people have type 2 diabetes, in which the body does not produce enough insulin or does not respond to insulin the way it should. A drug commonly used to treat type 2 diabetes is metformin, an oral hypoglycemic (lowers blood sugar). Metformin has been linked to certain side effects, the most common of which involve the gastrointestinal tract. More severe side effects are lactic acidosis and liver complications.
Common Side Effects
The most common side effects of metformin affect the gastrointestinal tract and include diarrhea, loss of appetite, metallic taste in the mouth, nausea and vomiting, flatulence, bloating, stomach ache and inexplicable weight loss. Gastrointestinal side effects are most common when people begin to take the drug or when dosage is increased. Long-term use has sometimes been linked to increased homocysteine levels, which can lead to cardiovascular disease and malabsorption of vitamin B-12.
Hypoglycemia
Hypoglycemia (low blood sugar) may also result from metformin use, although this is rare and most common in older patients, alcoholics and those with liver or renal complications. Usually patients who take metformin and develop hypoglycemia are also taking other medications.
Lactic Acidosis
An overdose may cause lactic acidosis (too much lactate in the blood) because metformin decreases liver uptake of lactate. This is the most severe side effect of metformin but is rare and seen most often in people with liver or kidney contraindications, other acute disease, and dehydration. Lactic acidosis may lead to death, so a patient who observes the symptoms must seek immediate medical help. Symptoms include weakness, sleepiness, low heart rate, feeling cold, muscle pain, trouble breathing, stomach pain and fainting.
Liver Complications
Liver damage is a possible but rare side effect, as shown in a study abstracted on PubMed of a patient taking metformin 850 mg twice daily who had developed liver disease.
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