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Pet Fasting Before Surgery: All Your Questions Answered

Pet Fasting Before Surgery

Fasting is commonly required before surgery, whether it’s for humans or pets. It’s a recommended pre-operation to-do to prevent complications that can be caused by the surgery itself or the general anaesthesia administered during surgery. But is it safe and necessary?

Pet fasting before surgery is crucial as it can prevent vomiting and aspiration, which may be fatal for your furry friend. It empties the stomach and allows little to no fluid to be regurgitated from the oesophagus or inhaled to the lungs. Ideally, your pet shouldn’t consume food or water prior to surgery.

Most pet owners will eventually have their pets go under the knife. Whether you have a dog, cat, or pocket pet, this guide can help ease you into the idea of fasting your pet before surgery.

To learn how long your pet needs to fast before surgery, including food or water, read on!

Why Do Pets Need to Fast Before Surgery?

Pets need to fast before surgery to prevent vomiting and aspiration during anaesthesia, which is fatal. Even eating or drinking small amounts during the fasting period can be dangerous, so it’s essential your pet doesn’t eat or drink before their surgery. 

Vomiting, particularly Gastroesophageal Reflux (GER) or regurgitation, is possible during surgery. In fact, Gastroesophageal Reflux Disease (GERD) is very common in dogs and cats.

Sedation for dogs is used to allow your pet’s organs to relax, except for the brain, heart, and lungs which continue to function. This includes the organ gatekeeping your stomach. When that relaxes, your pet’s stomach contents may rise back up to the oesophagus, and your pet may vomit. 

The chances of your pet vomiting are heightened because they are wheeled around frequently as tests may need to be done before surgery—from the waiting room to the x-ray room or another waiting room, then to the surgery room.

On the other hand, aspiration refers to the inhalation of stomach contents into the lungs. The organ (larynx) that prevents food from entering the lungs also relaxes under anaesthesia. When your pet aspirates, your furry friend can get pneumonia or, in some cases, pass away due to complications.

On rare occasions, esophageal strictures can also occur if your pet doesn’t fast before surgery. This complication narrows the oesophagus where stomach acid burns the lining of the oesophagus, then scar tissues heal over it.

For surgery to go without a hitch, not eating or drinking for as long as your vet recommends is essential. 

How Long Should Pets Fast Before Surgery?

Most vets will require your pet to fast from food for 12 hours before surgery. However, the fasting time for pets before surgery depends on the pet’s breed, age, the surgery being performed and the advice of your vet.

The time it takes for your pet’s stomach to empty before surgery can vary. Your vet may sometimes recommend a shorter time window of around 8 hours since your pet’s last meal. However, a 12 hour fasting window is usually the easiest to implement at home overnight, and this accounts for a range of variables such as slowed digestion or error. 

For that reason, a 12 hour fast before surgery is the most common recommendation. Some specific procedures may require your dogs to fast for up to 24 hours, though, so make sure you confirm that with your vet. Note that younger puppies and kittens may only be recommended to fast for 1 to 2 hours prior to surgery. 

Different types of pets have different fasting requirements. Ferrets, for instance, are required to fast for 4 hours, while rats only need to fast for an hour. Meanwhile, rabbits and guinea pigs do not need to fast before surgery.

For unplanned or emergency surgeries, it can be difficult to fast a pet for a full 12 hours. In these scenarios, your vet will determine when it’s safe to perform surgery, since an animal’s stomach may be empty after 4 hours. However, when fasting your pet at home, the safest approach for your pet is to stick to a 12-hour fasting window – or whatever your veterinary surgeon recommends. 

What Should I Feed My Pet Before Surgery?

In the days and weeks leading up to your pet’s surgery, you should give them the same food they usually get. Avoid giving them new foods or larger quantities of food prior to fasting for surgery, and feed them as normal. 

In the lead-up to your pet’s surgery, it’s important to keep things as normal as possible, including their diet. The time leading up to surgery isn’t the right time to experiment with new diets for your pet. 

Although it may seem like you’re doing a good thing by feeding them more before surgery or giving them new foods to spice up their regular diet, dietary consistency is best before major surgery. 

Can My Pet Drink Water Before Surgery? 

Water passes through an animal’s system more quickly than food. Keeping your pet from drinking for 2 hours is typically sufficient, so removing water from your pet the morning of their surgery is the most common recommendation. Of course, be sure to prioritise any specific instructions from your vet. 

Depending on the surgical services being provided and the age and size of your pet, there are different rules regarding drinking water before surgery. Be sure to follow the recommended fasting period your vet provides.

It’s best to avoid giving your pet any water immediately before surgery unless your vet specifically says it’s okay. It’s important to reiterate that you are not mistreating your pet by not giving them water before surgery. It’s completely safe for your pet to go without water during this period, and it wouldn’t be recommended by your vet if it was harmful. 

In fact, giving your pet water before surgery is likely to do more harm than good. At the minimum, the surgery may be cancelled or rescheduled if your cat or dog is given water. At worst, it may pose a safety risk during the procedure, which can lead to infection or death.

Is Fasting Dangerous for Pets? 

No, it is not dangerous for pets to fast. Most animals, including dogs and cats, are perfectly capable of fasting for extended periods before surgery. In fact, it’s more dangerous to give your pet food prior to surgery than it is to get them to fast. However, some small animals like rabbits and guinea pigs should not be fasted. 

In fact, there are some benefits to fasting. By stopping them from eating, pets can remove toxins from their body and allow them to repair and regenerate. Fasting even promotes cell renewal or cleansing (autophagy), allowing the body to fight viruses, bacteria, and worn-out and abnormal cells. Particularly for dogs, fasting is anti-inflammatory.

With those benefits, pets can certainly go without eating before surgery without endangering their health and life. A 12 hour fasting period for surgery is not dangerous for pets. 

However, fasting for very long periods can worsen gastric acidity. Excessive fasting above and beyond what your vet recommends can burn the lining of the oesophagus and cause esophageal stricture, in which scar tissues will heal over the burns and make the oesophagus narrow. That’s why it’s best to confirm with the vet how many hours your pet needs to fast, because it’s different for every animal.

In unique cases, like with rabbits and guinea pigs, fasting is very dangerous and shouldn’t be done at all. Fasting will likely lead to gastrointestinal stasis or gut stasis, which starts with a decrease in appetite and can cause the animal to pass away due to an overgrowth of harmful bacteria. However, this is based on the biology of these small herbivorous animals and doesn’t apply to cats or dogs. 

How Else Can I Prep My Dog for Surgery? 

To help prepare your pet for surgery, ensure their diet is normal in the lead-up to surgery and they don’t over-exert themselves while playing. You should also try and give them extra positive attention without playing too hard before the surgery. 

Of course, it is best to consult your vet on how to prep your dog for surgery, as every pet is different. But generally, to help your dog prepare for surgery, consider their pre-op activity, diet, medical records, and grooming and hygiene.

A day before your pet goes under the knife, avoid strenuous activities, such as long walks and rough play. These can increase how sore their muscles are post-op.

You may also want to get pre-anaesthetic blood testing to check for any underlying medical condition. This will check if your dog’s liver can process the drugs and medication during and after surgery and point out any abnormality in their blood cells and prevent excessive bleeding during surgery. 

A pre-anaesthetic blood test is recommended for dogs eight years old and above. Depending on the surgery, your pet might also need an x-ray or ultrasound in the lead-up to surgery. 

Before you bring your dog in for surgery, it’s important to ensure they are up to date with all of their vaccinations. As for hygiene, it is not ideal for dogs to bathe for 12 to 14 days after sterile surgery to keep the incision dry, so it’s best to bathe your dog before surgery. It’s also easiest and safest for the vet to operate on a clean dog. 

A routine dental check-up also wouldn’t hurt, as any untreated periodontal disease might let bacteria into the bloodstream.

Frequently Asked Questions 

What if My Pet Accidentally Eats Before Surgery? 

If your pet accidentally eats before surgery, you need to tell your vet, as it may be unsafe to proceed on schedule. Give your vet as much information as possible, like what they ate, what time they ate, and how much was consumed. This will help your vet determine when it’s safe to perform surgery.

What if My Pet Accidentally Drinks Water Before Surgery? 

Although drinking before surgery isn’t as bad as eating before surgery, your pet should avoid drinking water for at least 2 hours before the procedure. If your pet drinks water during the fasting period before surgery, you need to tell your vet, including how much water was consumed. 

How Long Should a Pet Fast Before Dental Surgery? 

Since dental surgery still involves a general anaesthetic, your pet should fast for 12 hours before the surgery, or whatever your vet recommends. Depending on your dog’s breed and the surgery being performed, the fasting time may differ. Make sure you follow the advice of your veterinary surgeon.


This article is published in good faith, for general informational and educational purposes only. Paws and More Vet Centre does not make any warranties about the ongoing completeness and reliability of this information. This article should not be used as a substitute for veterinary advice, including for diagnosis or treatment of a pet’s medical condition. Always consult a veterinary professional before making decisions on your pet’s health.