Metformin PRN?!?!

Last day of my family medicine rotation and I had a nurse practitioneer for my final patient of the day. Of course, she corrected me when I called her Mrs. instead of "Dr." She had been a diabetic for many years and we went over her insulin regimen. Apparently, she "tweaked" her own sliding scale and told me she takes metformin "as needed" and lispro at bedtime. Wtf? Do they not teach NPs about metformin increasing the sensitivity of insulin action? Did she not know lispro is a... Metformin PRN?!?!
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums