This is the recommended dosing
Step 1. 4-12 hours before the test take 4 aspirin (not Tylenol or Advil). This step may be repeated every 4-6 hours up until 4 hours before the test.
Step 2. 3-4 hours before your test, start by drinking 2, 8oz. glasses of water. Water can be substituted for with Cranberry or fruit juice, teas or even soft drinks. Then drink another 8oz. every 15 minutes for the next hour for a total of 6 glasses of water (48oz).
Step 3. In about 1 - 2 hours (depending on your system) you should be voiding ‘clear’ urine about every 15 - 20 minutes. Continue to drink 3-4 oz. more water to replace what you've voided every 20-30 minutes.
Step 4. 1-2 hours before the test, take vitamin B2 or B complex (about 10 times the daily recommended dosage). If the vitamins are time release, crush them before taking. You may also take vitamin B with each glass of water, 2 times the daily dosage, if you find it easier.