How long do dogs fast before leg amputation surgery?

Not a vet, but I've recently cared for a very ill dog who needed several procedures done, where general anesthesia was required. Obviously, it would be best if you could get your vet to weigh in, but if you can't reach them, I would withhold food starting at 8pm the evening before and no water after midnight. That may be overly cautious, but better to be too cautious, then not enough. Then, the morning of surgery make sure your vet is aware of exactly when your dog last had food and water. Another thing you might try, would be to call a local emergency vet and see if they could give you some guidance. I would especially try to reach out to the e-vet if your dog has any metabolic health issues. Good luck to you and your poor pup.

/r/AskVet Thread