Definition: A biguanide is a class of type 2 diabetes medicine, and metformin is the one in use in the US. MedlinePlus says metformin lowers the amount of sugar absorbed from food and made by the liver, and increases the body's response to insulin. It is not used for type 1 diabetes.
Besides plain metformin, many fixed-dose combination pills pair it with another medicine:
Some, such as Xigduo XR, use an extended-release form of metformin taken once a day.
In the label's placebo-controlled trial, diarrhea affected 53% against 12% on placebo, and nausea or vomiting 26% against 8%. Diarrhea led 6% to stop. Combination labels such as Janumet and Jentadueto start low and raise the dose gradually to reduce these stomach effects. The metformin label approves it, along with diet and exercise, for adults and for children 10 years and older with type 2 diabetes.
Metformin has a boxed warning for lactic acidosis, a rare but sometimes fatal build-up of lactic acid. Risk factors named include kidney impairment, age 65 or older, contrast dye studies, surgery, heavy alcohol use and liver impairment.
Several brand names can all contain metformin. Logging the full product name shows when two of them overlap, which a quick look at the brand names alone can miss. Logging stomach symptoms in the first weeks, and after each dose step, also shows whether they eased as the label describes for a gradual start.
Read more on Dose Track: Metformin guide · Metformin side effects · Metformin before contrast dye or surgery · Alcohol and metformin