Metformin
"My husband and I are both on this medicine.  He takes 1000 mg morning and evening. I take the max at 850 mg each meal.  We have to keep a packet of desiccant in the bottle to absorb the horrible fishy smell.  We both have the side effect, even years later, of bloating, gas, and flatulence.  We call this pill our "gas" medication.  But it lowers our blood sugar with few other side effects.  If we're out, we take it on our return home if possible to prevent inflicting our flatulence on others."