Xylitol is the one on this list that isn't a food. It's a sweetener, it's in things nobody thinks of as food at all, and the label often doesn't tell you how much is in there. It is also fast: the MSD Veterinary Manual reports signs beginning within 30 minutes of a dog eating it, and the dose that starts causing trouble is small enough that a handbag can hold several times over.
- Yes, to dogs, and at two separate doses that cause two different problems.
- Above about 100 mg/kg: a rapid insulin release and dangerously low blood sugar.
- Above about 500 mg/kg: some dogs develop severe liver insufficiency or failure.
- Signs can start in 30 minutes - or be delayed 12-18 hours. Liver signs may not appear for 24-48.
- Cats are not at risk. MSD is unusually direct about this.
- It hides in non-foods: toothpaste, chewable vitamins, medicines, sunscreen, deodorant.
What xylitol actually does to a dog
In people, xylitol has essentially no effect on insulin. In dogs it does something quite different, and MSD puts it plainly: "In dogs xylitol stimulates a rapid, dose-dependent insulin release that can result in profound hypoglycemia."
That is the whole first problem in one sentence. The dog's pancreas reads xylitol as a large sugar load, dumps insulin accordingly, and the blood sugar falls off a cliff - because there was never any real sugar there to match it. Dose-dependent is the part worth holding on to: more xylitol means more insulin, which is why the amount genuinely matters here in a way it doesn't for some other toxins.
The second problem is liver damage, and it is less well understood. MSD: "The mechanism for hepatic necrosis is unclear but is hypothesized to be the result of either ATP depletion or the production of reactive oxygen species." It happens at a much higher dose, and not to every dog that reaches it.
The two doses
MSD publishes both thresholds in mg per kg of bodyweight:
- "Doses of xylitol greater than approximately 100 mg/kg (45 mg/lb) have been associated with hypoglycemia in dogs."
- "Some dogs ingesting xylitol at doses > 500 mg/kg (227 mg/lb) may develop severe hepatic insufficiency or failure."
Turning those into whole dogs. This table is our arithmetic on MSD's two figures - MSD publishes the mg/kg and nothing else:
| Dog | Rough weight | Hypoglycaemia above | Liver risk above |
|---|---|---|---|
| Chihuahua, Yorkshire terrier | 3 kg | 0.3 g | 1.5 g |
| Miniature dachshund, Pomeranian | 5 kg | 0.5 g | 2.5 g |
| French bulldog, cocker spaniel | 12 kg | 1.2 g | 6 g |
| Border collie, springer spaniel | 20 kg | 2 g | 10 g |
| Labrador, German shepherd | 32 kg | 3.2 g | 16 g |
A gram is not very much of anything. For a small dog, the hypoglycaemic threshold is a fraction of a gram - which is the point at which it stops being a question of whether your dog raided the cupboard and becomes a question of whether it got hold of one thing from a bag.
Every article you will read on this subject wants to convert those grams into pieces of chewing gum, and we have deliberately not done it.
Xylitol content varies enormously between brands and between products within a brand, and manufacturers are generally under no obligation to state how much is in there - "xylitol" appears in the ingredients without a quantity. A piece count derived from one brand's formulation, presented as a general figure, would be a fabrication wearing the costume of precision, and someone would use it to decide not to ring their vet.
What to do instead: take the packet with you. The ingredients list, the pack size and how much is missing are what let a vet estimate the exposure, and they can do that far better with the wrapper in front of them than you can with a number off the internet.
Where it hides
This is the part that makes xylitol different from chocolate or grapes. It is not shelved with the food. MSD's own list of sources:
- Obvious: sugar-free gum, sweets, mints and baked goods
- Less obvious: peanut butter - which is why we wrote the peanut butter guide alongside this one, because peanut butter is a thing people deliberately give dogs
- Not food at all: toothpaste, chewable vitamins, medications, sunscreens, cosmetics, deodorants and hair care products
Two practical consequences. A dog that chews a tube of toothpaste or a bottle of chewable vitamins has had a xylitol exposure, not just a mess. And human toothpaste should never be used to brush a dog's teeth - use a pet toothpaste, which is formulated to be swallowed.
The timeline, and why "he seems fine" isn't the end of it
MSD gives two separate windows, and they do not overlap neatly:
- Hypoglycaemia: "Clinical signs of hypoglycemia can develop within 30 minutes after ingesting xylitol or may be delayed up to 12-18 hours."
- Liver injury: "Clinical signs of liver injury may not occur until ≥ 24-48 hours after xylitol ingestion."
So a dog can look completely normal for most of a day and still be heading for a hypoglycaemic crash, and a dog who sailed through the first day can still develop liver failure on the second. Neither window is a period during which you can conclude anything by watching.
The signs of low blood sugar, per MSD: vomiting, weakness, ataxia (wobbliness), lethargy, seizures and coma.
What to do if they've eaten some
- Ring your vet immediately. This is one of the genuinely time-critical ones - 30 minutes is inside the window in which signs can start.
- Take the packaging with you. As above: it is the only reliable way to estimate the dose.
- Don't wait for symptoms and don't wait for morning. The delayed presentations are the dangerous ones precisely because they look reassuring.
- Don't give sugar unless your vet tells you to. It sounds logical, and there are circumstances where a vet will direct you to, but doing it unprompted can complicate the picture on arrival.
- Mention it even if it was a non-food. Toothpaste, vitamins and sunscreen do not sound like poisoning, and they are.
MSD's treatment is "early GI decontamination", "administration of IV dextrose", and "monitoring of liver enzyme values and management of liver insufficiency" - which is why exposures often mean a stay rather than a visit.
In the UK, Animal PoisonLine (01202 509 000) is a 24-hour service for owners, run by the Veterinary Poisons Information Service; there's a per-call fee. In the US, the ASPCA Animal Poison Control Center is on (888) 426-4435, 24 hours, also for a fee.
Cats
For once, an unambiguously good answer. MSD: "Dogs are the only domestic species in which xylitol toxicosis has been reported; cats are not at risk for hypoglycemia or liver injury."
That is about as clear as veterinary toxicology gets, and it is a real difference from chocolate and onion, where cats are as susceptible as dogs or more so. It is worth knowing in a multi-pet house: the same spilled packet is an emergency for one animal and not the other.
Not sure about something else your pet got into?
Check any food instantly in the Supernormal app's food safety checker - or try the Pet Food Safety Checker for the foods we've covered so far.
Related guides: Pet Food Safety Checker · Can Dogs Eat Peanut Butter? · How Much Chocolate Can a Dog Eat? · Can Dogs Eat Grapes or Raisins?