Why can’t I feed my dog before surgery?

Why can’t I feed my dog before surgery?

When your dog is getting surgery or any procedure that they need to be sedated for, your vet will ask you not to feed your dog for up to 12 hours before they get dropped in. Here’s why it’s so important to starve or fast your dog before surgery. 

Why do I have to fast my dog before surgery?

Your vet team wants your dog to be as comfortable and pain-free as possible during the whole procedure and the drugs we use before, during, and after surgery can make your dog nauseous. 

If your dog retches and vomits up their food while sedated, they could inhale it into their lungs (technically, it’s called aspiration). They can choke (and possibly die immediately), or it can lead to a potentially life-threatening lung infection called aspiration pneumonia. 

While vets and veterinary nurses are trained to deal with these kinds of emergencies, we prefer to prevent it from happening at all—by asking clients not to feed their dogs. 

Why can dogs vomit during surgery?

This isn’t your vet being overly cautious. The whole anaesthesia procedure can make dogs get sick. 

After the vet team puts your dog under a general anaesthetic, they lie them down and begin preparing them for surgery by shaving and scrubbing the area that will be operated on. Once your dog is prepped, they get moved into the operating theatre. 

All this movement, combined with the long time lying down (often on their backs) can make some dogs regurgitate the contents of their stomachs. This is what can cause them to choke or suffer from aspiration pneumonia.

Even if it doesn’t kill them, the acid in their vomit can damage their oesophagus and make it hard for them to swallow. It’s just not healthy for them.

Can my dog still have water?

Yes, water is fine to give an animal fasting for surgery. 

Most vet teams prefer when owners let their dog have access to water before surgery so that we know they are fully hydrated when they come to see us that morning.  

What if I accidentally feed my dog when they should be fasting?

Accidents happen, and owners often feed the dogs that they are meant to be fasting for surgery. 

If you accidentally feed your dog before surgery, don’t give them any more food and call your vet as soon as you can. 

Depending on when you fed your dog, the vet team may be able to reorder their surgical list so that your dog’s surgery is performed later in the day. If they can’t, they will reschedule you for another date. 

Your dog’s safety is the surgical team’s highest priority, and they will make these calls based on what’s best for your dog—not what is most convenient for you. 

What if my dog is begging for food while fasting?

bing with kong wobbler

Ignore them. You know why they haven’t had dinner, even if they don’t.

Unfortunately, you don’t speak dog so can’t reason with them or explain why they don’t get to eat. The best thing to do is just ignore their begging. They will keep it up for twenty minutes, sigh, then walk away in a strop. 

If they’re the kind of dog that will help themselves to food or raid the fridge, keep an extra-close eye on them! If they are able to eat, your vet will need to reschedule. (This is another great reason to crate train your dog.)

(When we fasted Bing before his last dental procedure, he attempted to break into the fridge. When that failed, he tried to call the local SPCA. He misdialed.)

What if my dog is on routine medications and fasting?

Check with your vet when booking the surgery. Some medications, such as heart meds, have to be given regardless of whether your dog is fasting or not. 

If you’re reading this after your vet’s office is closed, bring your dog’s meds when dropping them off for surgery in the morning and explain that you weren’t sure whether or not to give them their morning dose. The nursing team will handle the rest. 

Don’t give your dog dewormers, flea treatments, or other semi-regular medications for the two days before surgery. If your dog reacts to that medication  the surgery may have to be delayed. Gunther will occasionally get explosive diarrhoea post-dewormer, which would dehydrate him and force the vet to reschedule any upcoming surgery.


Vets seldom ask you to do something without a very good reason. They always have your dogs’ best interests in mind. They don’t want you to starve your dog to be mean, it’s for their safety.