I’m not sure of the exact dosage because she passed away in 2015 (she was 97). I just remember that it was a small white or yellow pill. It really helped. She practically refused to drink water. She would start acting strange and have symptoms like she had had a stroke. We would call an ambulance and it would turn out to be a uti. After the trimethoprim this did not happen. You could ask your doctor. Maybe he could start you on a low dose and increase if it doesn’t help at first. I hope it works for you. ❤️