How long does it take for Bactrim to work for UTI?

Hi Vealparm,
Chuck is right. You should feel some relief.
The only possibility is that the organism causing the UTi isn't sensitive to Bactrim.
This is why they do cultures and sensitivities.
The first 24 hours identifies the organism. The 2nd 24 hours is which antibiotic is the most sensitive to to that organism.
You need to call your doctor.
Good luck
;-)

Vealparm; for sure by today you should be noticing something, if not please call your doctor. and makes sure you are drinking plenty of juice or water and if you are where it is warm it is best to stay out of the sun as much as possible But 3 days you should not be feeling the effects of the UTI if you are taking the Bactrim DS double strength. have a good day