Hi, Just Wanted To Know If The Darkening Of The

hi, just wanted to know if the darkening of the urine from taking Metronidazole 500 mg is ok?? iv taken this before but didn't notice it before. i have bit of pain in my stomach which i usually do but haven't got the diarrhea yet. i started taking the pills yesterday evening so only had 3 so far. I'm taking it for infection which is the only pill that gets rid of it! could you let me know asap please. thanks