Nitrites usually do not appear in urine and if they do, it usually indicates that something unusual is going on in the urinary tract. Since this isn't something people can discern with the naked eye, to properly tell whether there are nitrates present in urine, a urine test is needed.
A common cause of nitrates to appear in urine is bacteria. Some bacteria cause a urinary tract infection (UTI) that induces a chemical reaction in the body to make an enzyme that changes urinary nitrates to nitrites. See more on urine nitrates.
You have several options to test your urine to understand its chemical composition. The easiest test is the over the counter urine dipstick test. One problem with the test is that most people are not qualified to interpret the findings of the test because the test simply shows what the chemicals are that make up the pee. To make a proper diagnosis, you should seek the help of a qualified healthcare professional such as a doctor who can correctly diagnose the problem and prescribe treatments.