Dog reaching to eat a cookie containing xylitol.

Xylitol Toxicity in Dogs

Although dogs are sweet, they need to be kept away from certain types of sugar substitutes. Xylitol is a class of sweetener known as sugar alcohol that is made from the bark of hardwoods and corncob remnants from ethanol plants.

Products that Contain Xylitol

Xylitol can be found in:

It can be purchased in bulk to use in baking, and is often used as a sugar substitute in “sugar free” products. Because it is so widely used, all products should be checked for xylitol or “sugar substitute” prior to feeding them to your dog.

Although xylitol is safe for human consumption (and known to have antimicrobial properties, retain moisture, and prevent cavities), it can be fatal when ingested by dogs. There has been less research on other pets, including cats and ferrets, but it should generally be avoided in all non-human animals. Like sugar, xylitol signals to the pancreas to release insulin, a hormone that allows the body to absorb sugar and turn it into energy. However, although dogs can tolerate regular sugar, xylitol is absorbed rapidly and can cause a spike in insulin. Because xylitol is not sugar, a spike in insulin causes severe hypoglycemia that can result in weakness, collapse, and seizures.

Dangers of Xylitol Based on Amount Consumed

Dosages of xylitol that are 75–100 mg/kg (34–45 mg/lb) can be associated with hypoglycemia in dogs. Hypoglycemia, or low blood sugar, is easily managed in a hospital setting with intravenous sugar supplementation. This can be continued as long as necessary to maintain a normal blood sugar level. In addition, frequent small meals can help. Once a dog is able to maintain a normal blood sugar level on their own, they can be discharged from the hospital. This can take up to 48 hours.

Dosages >500 mg/kg (227 mg/lb) can lead to severe hepatic injury or failure. The mechanism of the liver injury is unknown, which makes prevention and treatment symptomatic and empiric. Protecting the liver involves supplementing the body with all the substances made by the organ, essentially allowing it to rest and heal. The liver makes sugar and vitamin K (a vitamin required in coagulation), both of which can be supplemented by injection in a hospital setting. It also makes a compound known as glutathione, which is an antioxidant important for organ health and prevention of cellular death.

Glutathione can be supplemented by giving S-Adenosylmethionine (SAMe) orally, which is a synthetic version of the compound. Another helpful oral liver supplement is milk thistle. Milk thistle is a flowering herb related to the ragweed family that has been proven to support organ function. Cysteine, an amino acid that is a precursor to glutathione, can also be given in a modified form as an injection or by mouth, known as N-acetylcysteine.

Treatment for Xylitol Toxicity

Because toxicity can be expected up to 72 hours after xylitol ingestion, liver values in dogs should be checked up to 3 days or longer if elevated or increasing at any point. Approximately 75% of the liver needs to be injured or damaged before an elevation in values or change in function is expected. Therefore, if a dog is known to have eaten a dangerous dose of xylitol, liver protection should be started immediately to prevent any further damage regardless of initial blood work results.

The quantity of xylitol in products is often proprietary information and difficult to calculate. Therefore, a veterinary toxicologist should be consulted to determine the estimated xylitol dose in any given product (ex: ASPCA Animal Poison Control Center).

If xylitol was ingested by a pet, they should be evaluated by a veterinarian immediately, as hypoglycemia can be seen within minutes to hours of ingestion. The veterinarian and poison control toxicologists can make further recommendations after your pet has been evaluated and treatment initiated if needed.