STI testing

(please remove if not allowed but think it’s worth the question as it could happen to anyone.)

I can’t find any straight forward information on this but here we go.

First off i’ve not got anything STI related. But was wondering what the royal navy’s policy with this is. Can getting an STI be justified or is it straight up bar from the service?

Only asking because i think i briefly read something about this topic when joining but unsure what the score was with it.