I was on Macrobid for 5 days from Friday to Tuesday (prescribed by a minor emergency clinic near my house) and then had blood drawn 2 days later on Thursday for a routine check-up. The only abnormal result was a "mild elevation" in liver enzyme AST. Could the Macrobid have caused this elevation? It didn't occur to me to ask that question when the doctor's office called to give me results, although I informed them of having taken the meds during my initial interview with the nurse.