Only when you need it
Poop check
Size, shape and texture matter — not how many there are. Photograph the suspicious droppings in good light, close enough to see each one, and Dr. Hopps reads them against what a healthy rabbit produces.
No droppings for 12 hours, or not eating? That's an emergency →A photo cannot rule anything out. If your rabbit is hunched, cold, not eating, or has made no droppings for 12 hours, go to a vet now whatever this says.