Lumbar pain after a urinary tract infection may indicate that the infection has spread to the kidneys, which is a more serious condition that requires medical intervention. In such a situation, you should consult a doctor immediately.

Do not stop taking furagin and cranberry preparations unless your doctor tells you otherwise. Also, drink plenty of water to help flush bacteria out of your urinary tract.

If you are not able to make a face-to-face visit, I attach a link to the online teleconsultation:
https://www.gdziepolek.pl/telekonsultacja/z-internista