The diabetes urine test is to detect tiny amounts of protein, which is the earliest sign of kidney damage, usually either due to longstanding diabetes or longstanding high blood pressure. If you have this, tablets called ACE inhibitors have been shown to reduce it's progression, they also lower blood pressure, and keeping blood pressure low also helps protect the kidneys, but they have an additional effect independent of the BP effect.
BUT - the condition should only be diagnosed once a urine infection has been excluded by sending a urine sample for culture & sensitivity, and if at least 2 out of 3 samples are positive for protein within a 3 month period (at least that's out guidelines). Lots of things can cause transient increases in urine protein, so one raised reading shouldn't mean them rushing into diagnosing & treating.
If you've already started the antibiotics then it'll probably be too late to send a sample to test for infection - if you haven't I'd insist on one being sent - and I'd be asking if this has even shown on any of your previous urine tests before agreeing to lifelong medication.