Most cats pee two to four times daily, but there's no definitive answer as to how often your kitty should urinate per day. What's important is consistency. If you notice a change in your cat's urination routine, consult your veterinarian.
If your kitty's drinking and urinating more than she used to, or if she normally seems to pee quite a lot, tell your vet. Increased thirst is called polydipsia, and increased urine volume is called polyuria. These can be symptoms of a number of health problems, many of which are potentially fatal.
Kidney failure is probably the biggest concern. Diabetes, liver disease, hyperthyroidism, elevated blood calcium levels, pituitary gland dysfunction and a uterine infection are others.
Your vet will examine your cat and consider any other symptoms, then decide what tests to run. Also, if your kitty is on any new medications or supplements, check the label; polydipsia and polyuria are common side effects.
If your kitty urinates just a little at a time but more than five or six times per day, her condition is pollakiuria. Again, consult your vet if your cat has started peeing more often. This is often a telling sign of a urinary tract or bladder infection or urinary tract stones. It can also point to diabetes, renal failure, trauma affecting the urinary tract, certain types of cancer and incontinence. The latter is not uncommon in elderly cats.
There's also the possibility your kitty is doing some good old-fashioned scent marking. Notice whether your cat is picking out particular places to pee, especially places where people and other animals are prone to intrude.
If your cat is peeing infrequently and in small amounts, that condition is called oliguria. Usually, this is symptomatic of little urine actually being produced, rather than an inability to void what is being produced.
Dehydration is a primary cause; it's most likely in hot weather. Low blood pressure, kidney problems, liver dysfunction and trauma affecting the urinary tract are other conditions that commonly underlie little urination. Again, a trip to the vet's office is in order. Be prepared to describe any other symptoms you've observed.
It's completely abnormal for a cat to not urinate at all, and this condition is life-threatening. The best-case scenario is that your kitty has an obstruction in her urinary tract.
If nothing's blocking the flow of urine, your kitty is probably quite ill. When her body isn't producing any urine, that's called anuria. Most often this condition is a symptom of acute kidney failure, which stems from kidney disease, congestive heart failure, ingestion of toxic substances or one of numerous other very serious causes. If your kitty stops peeing altogether, she needs emergency veterinary care.