Metformin
insulin resistance syndrome
"I took Metformin Hcl ER 500 mg 2xday, for 2  years. I never felt quite well w it, especially  the constant fatigue. So I stopped. 

Now , 11/16, I was prescribed it again, & almost immediately became lethargic,  weak, plus experienced extreme muscle pain & stiffness in quadriceps (frontal thigh muscles) which caused my legs to become so weak & stiff, walking was difficult."