Human: What are the most common side effects of taking metformin? Assistant: 
The most common side effects of taking metformin include nausea, vomiting, stomach pain, bloating, diarrhea, constipation, gas, headache, and dizziness. Other less common but more serious side effects may include an allergic reaction, lactic acidosis, liver damage, and a decrease in kidney function. It is important to consult your doctor if you experience any unusual symptoms while taking this medication.