Can a UTI or Kidney Infection cause light bleeding between periods?

UTI is likely the cause. The cramps are an indication and the blood. Do you have a pain after you urinate? Do you have a major urge to pee constantly? Those are symptoms of a UTI. Kidney infection/stones cause SEVERE back cramping near the back in line with the ribcage, my sister used to ROLL on the floor in pain when she had hers. They say its worse than labor pains...if you have mild to moderate cramping I would shoot for a UTI and go to your GYN and get tested. An untreated UTI can lead to major problems so get this checked out asap.