Before the procedure. Preparing for a urinalysis is simple. Typically, no special steps need to be taken. People are generally allowed to eat and drink normally prior to the test. The doctor will need to know what medications, vitamins and supplements a person usually takes, as some of these can interfere with the results of a urinalysis. For women, it is important to let the doctor know if you are menstruating at the time of the test. Depending on why the doctor has ordered the urinalysis, people may be asked to avoid certain foods, drinks and medications for 24 hours prior to the test. Things to avoid may include medications, certain fruits and vegetables, alcohol, caffeine and other items that may interfere with particular urine tests. Check with the doctor prior to testing to determine if any special precautions need to be taken.