They occur when bacteria get into the normally sterile environment of the urinary tract.
Symptoms can range from very mild to excruciating.
There may be pain or burning upon urination or pain even when not urinating. You may experience a frequent urge to urinate, sometimes right after you have just finished. You may have some of the sensations of urinating when nothing is passing. The urine itself may turn cloudy or reddish, signaling the presence of blood. You may feel tired or worn out.