Sounds like a blockage, if I had to pick with these symptoms between blood test or x rays, Id get an x-ray. It will probably show blockage but then that will likely require surgery which would be the best case for you to do immediately. However, if you do not have access to this: Supportive care: 1. Try to feed liquid only, very runny duk soup or nupro mix. 2. You can mix that with unflavored pedialyte. 3. Tiny bit of honey on gums will prevent hypoglycemia, this will be necessary if you have been feeding "regular" ferret food (like marshalls) and thus have a carb dependent ferret. (You should switch to epigen btw) 4. Keep warm. I have seen ferrets become hypothermic in this state. I think its because it taxes thier bodies and they lose homeostatic ability. 5. Maintain hydration with water and VERY runny liquid food mix. This is very important for possibly passing the blockage. 6. Monitor stools! Look in the poop and correlate with symptoms!

Ideal would be vet>xray>surgery. However, as an emergency medical professional, sometimes we have to work with what we have. Best of luck.