(… yes, even if you don’t have symptoms.)

A general urine screening isn’t enough to confirm that you have a negative STI status, because sexually transmitted infections can occur in three sites on your body: Genitals, throat, and the rectum. 
Even if your genitals test negative for a sexually transmitted infection (STI), you may still test positive somewhere else.
You can also have what’s called a “co-infection,” which is when you experience two or more STIs at the same time. 

The most common symptom of an STI is no symptoms at all. 

While many STIs make their presence known through symptoms like itching, burning, discharge, or visible sores, many people can be asymptomatic. (That means you have an STI but aren’t experiencing any symptoms.)