What is your bunny currently eating and how much? What were you doing before to keep weight on her? And you haven’t noticed any behavior changes? Does she eat normally? Or does she eat more slowly? Did the vet do x-rays? Thorough tooth exam? Something seems to be missing here.

Does she get any pellets? Some bunnies just need them, some don’t necessarily.

If everything else was good, I’d still suspect the teeth. Some buns have very sensitive mouths and will become picky if they have even very small spurs. The bun might still eat but not as much as she ideealy should, and she might not chew the food as properly as she should – that can in turn affect weight and how the stomach/intestines process the food.

How does her poop look? Any changes in size, shape and/or amount?

It’s often difficult to determine how much hay a bunny actually eats, since we always give a surplus.

Definitely would proceed with further scans/imaging (x-rays or skull CT) to rule out a dental issue.

my previous rabbit had sudden unexplained weight loss and excessive thirst. His blood results never yielding anything alarming. He was a frenchie, and went from almost 7kg to 4kg. It was undiagnosed E. cuniculi impacting his kidneys (I have no idea how or why it never showed on his bloods). Otherwise his behaviour was normal, it was only when he later developed a limp followed by full blown hind limb paralysis that the EC was diagnosed.

I’m not saying it’s the likely cause, but just throwing an avenue to investigate if imaging came back with no explanation.

Em – EC tests are notorious for having false results, so what you experienced isn’t unusual.

I agree with the others. Something is definitely missing here. If she is getting appropriate food, then something else is going on. I would suggest a more thorough look at her teeth to rule that out. This needs to be done under anesthesia. They can’t just glance at her front teeth and say she’s good. Once that is ruled out, then I would look into other causes like EC or some underlying issue.