Medical issue... Any advice is appreciated.

Hello. I took my 5 year old female cat to the vet because yesterday she committed green/yellow stuff with a bit of hair twice, then didn't eat and was extremely lethargic. The vet examined her and didn't find anything, took some blood (waiting for results), gave her sub-q fluids (minor dehydration), gave her some anti nausea med and sent her home. She it still lethargic with no change. She did have a normal bowel movement this morning, so that rules out an obstruction. Any ideas on what could be going on???? Just the visit today was $500, luckily I bought the Healthy Paws insurance -- we'll see how the claims process is.

Did this happen before she'd eaten breakfast yesterday? Green/yellow liquid could be bile, possibly indicating excessive acid build up. That's the only explanation I can think of, but wouldn't account for the lethargy.

IBD is a possibility with those symptoms, but there really isn't enough information to go on so far. I hope you find out what's going on with her soon, and that it's easily treated

In the meantime, make sure she's warm and try to get her eating again.

The same happened with my cat on monday, it turned out it was feline hepatic lipidosis, but that was due to very specific circumstances during these past weeks(overweight, stopped eating for a while) , so I don't think it's the same,or I hope not, didn't she have any fever?, I hope it's nothing serious and that she just ate something bad, but you should better wait for the tests and it's good that you took them to rule out anything serious, hopefully it's not the case.

Did they check her abdomen and bowels?  Wondering if she's blocked or constipated.

Is she doing any better today?  Did you get the blood results back yet?  Is she eating anything at all?  It's very important that she eat something, even if you have to "force" feed her via syringe, as cats cannot go more than a day or two without eating or they can develop worse issues, as referenced above.  (hepatic lipidosis)

If there is no improvement yet, please let your Vet know.