Why don't you need to check Vancomycin levels if it is given orally but you do for IV?

I know that patients given IV Vancomycin need to have Vancomycin levels checked. But there was a patient I saw being treated with oral Vancomycin for C Diff, and they were not doing Vancomycin levels. Surely this is still important?

Authored By Jessica Michaels on Wednesday 10th October 2012