Barbara returns to your office a couple weeks later and repo…

Barbara returns to your office a couple weeks later and reports significantly worse deep muscle aches, and has also developed generalized weakness and notes her urine has “looked like tea” the past 2-3 days. Upon further questioning of her symptoms Barbara reports she didn’t come back sooner because she thought her urine was dark because of the UTI she is being treated for. You call the Urgent Care she was seen at & discover she is on Cipro. What is the most urgent lab to order?