Join Date: Jun 2008
Location: northern Minnesota
If she is able and willing to eat AND keep food down tomorrow, then you may be able to hold off on the bloodwork. You need to understand, however, that even if she does start eating and keeping food down, that doesn't necessarily mean that damage hasn't been done by the Metacam. Bloodwork is the only way to check her organ function and know for sure.
If she can't or won't eat or can't keep food down tomorrow, I'd definitely recommend taking her to a vet immediately for bloodwork. Any cat who doesn't eat for more than 24 hrs is at risk of developing potentially fatal Hepatic Lipidosis, and the longer she goes without eating her normal amount of food, the greater that risk becomes.
Vomiting in apparent response to Metacam is a HUGE red flag for me.