I keep postponing toilet breaks at work. How do I raise that without discussing my bowel symptoms with everyone?

The shop has one staff toilet behind the stockroom, and I am often alone on the till. When somebody finally relieves me, I say I am fine because a queue has formed. By the time I get home, the urge to go has often passed.

I have been dealing with constipation and am seeking advice about it. I cannot know that the shift pattern is the whole cause, but it is part of what I need to explain.

[NHS advice says not to delay when you feel the urge to poo and recommends medical advice for ongoing problems](https://www.nhs.uk/conditions/constipation/).

My supervisor says to "just ask" for cover. I have asked, but there is no agreed way to get it when the only other colleague is unloading a delivery. What wording would turn that reassurance into a practical arrangement without giving the team a description of my bowel habits?