How Often Should Someone Urinate?

It is normal to urinate about 6-8 times a day for a normal adult, assuming they consume at least about 2 liters of fluids per day.

Urinating more?
Can be due to increased intake of water as the kidneys promptly respond to the stimulus!
However certain medical conditions can increase frequency of urination, such as a urinary tract infection, an overactive bladder, or due to certain medications a person is taking for treatment of blood pressure or their heart.
In men, enlarged prostate can cause increased urination even at night.

Urinating less? Are you drinking enough fluids? Are you dehydrated? Are the kidneys working? Some people with end stage kidney failure on dialysis have been known to completely stop producing urine and when they receive a kidney transplant, they start urinating again.
An enlarged prostate and other obstruction anywhere in the urinary tract (like a kidney stone) can block urine from coming out.
Having a very low blood pressure from serious blood-Bourne infections, heart failure, or liver failure can also cause low urine production.

If you are concerned about the frequency of your urination, you should speak to your doctor.