Metformin commonly causes side effects like nausea, diarrhea and bloating. More serious side effects involve low blood pressure and lactic acidosis. Overview: Metformin is medicine you take to help keep your blood sugar from getting too high. Common side effects may include stomach problems, such as diarrhea, nausea, vomiting, stomach pain. Common side effects of metformin hydrochloride tablets include diarrhea, nausea, vomiting, wind (flatulence), indigestion, and headache. These side effects occurred in 5% or more of patients in the US clinical trial of using metformin for type 2 diabetic patients. Common metformin side effects include diarrhea, nausea, and vomiting. It can also cause fatigue, weight loss, and low vitamin B12 levels. While uncommon, metformin can also cause blood glucose (sugar) to drop too low and lactic acidosis. In severe cases, these side effects are medical emergencies. Metformin can cause side effects in some people. Learn about its mild and serious side effects, as well as factors that can increase your risk. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Side effects of metformin include loss of appetite, bloating, heartburn, gas, nausea, and vomiting. Drug interactions, dosage, and pregnancy and breastfeeding safety information should be reviewed prior to taking this medication. Metformin can cause side effects that range from mild stomach problems to rare but serious complications. The most common metformin side effects are diarrhea, nausea and vomiting, gas and bloating, stomach pain, indigestion, a metallic taste in the mouth, tiredness, and headache. Metformin, which is used to manage blood sugar, can cause side effects. Learn about its common, mild, and serious side effects and how to manage them. Many of the warning signs are similar to some metformin side effects, such as stomach pain, dizziness, and weakness. Others are numbness or a cold feeling in your limbs, or changes in your.