I learned a tactic early in my working life, not for being late, but for taking sick leave; but it might work in your case. The trick was useful for dealing wit

I learned a tactic early in my working life, not for being late, but for taking sick leave; but it might work in your case. The trick was useful for dealing with those annoying HR types who like to harass people for things like sick notes from doctors and stuff. The first step is to be very concise or even curt when explaining tardiness (let's call it professionalism). If you're feeling generous, something to the effect of "I have a medical problem"; don't offer to explain because really, anything else is none of their business. Say it with conviction and complete confidence; remember, in your case, you're doing them a favor, remember that. If they drop it, good; mission accomplished. If they lack the couth or good sense to spare you your dignity, then there is no reason to spare them theirs. Now is the time to deploy in appropriate detail precisely the reason for your tardiness. Be sure not to soften the language with acronyms like "IBS", "spastic colon" is your go-to here. It's usually better to have these conversations in private, but if someone is so lacking in professionalism that they make the mistake of confronting you publicly, then punish them without mercy. Don't be the least bit shy. Even though your colleagues may not appreciate the moment, you're doing them and yourself a great service. The idea is to terrify the questioner so thoroughly that they never think of confronting anyone about a personal medical/health/hygeine/etc issue, ever again.