How the dose is calculated
Xylitol is a sugar substitute. In dogs it triggers a large release of insulin, which can drop blood sugar fast, and at higher doses it can destroy liver cells. Vets judge the risk by the dose per kilogram of body weight:
Dose (mg/kg) = grams of xylitol × 1,000 ÷ dog's weight (kg)
1 lb = 0.4536 kg
Worked example: a 20 lb dog eats 5 pieces of gum
20 lb is 9.07 kg. If the label says 0.4 g of xylitol per piece, 5 pieces is 2 g, or 2,000 mg. 2,000 ÷ 9.07 = 220 mg/kg. That is above the ~100 mg/kg level linked to low blood sugar, so this dog needs a vet now. For this dog, about 0.9 g reaches the low blood sugar level and about 4.5 g reaches the liver failure level.
The thresholds
| Dose | What has been reported |
|---|---|
| Above about 100 mg/kg (0.1 g/kg) | Low blood sugar (hypoglycemia) |
| Above 500 mg/kg (0.5 g/kg) | Severe liver failure in some dogs |
These levels come from the Merck Veterinary Manual chapter written by an ASPCA Animal Poison Control Center veterinarian (reviewed September 2024). They are not a guarantee in either direction. Below 100 mg/kg the calculator still tells you to call, because the amount you enter is usually a guess.
Where xylitol hides
Merck lists sugar-free gum, candy and mints, some peanut and nut butters, baked goods, toothpaste, vitamins and supplements, sugar-free liquid medicines, and even some sunscreens and cosmetics. Gum is the classic case, and xylitol content varies a lot between brands, so look up the exact product or keep the wrapper.
What happens next
- Signs of low blood sugar can start within 30 minutes: vomiting, weakness, wobbliness, collapse, seizures. With some gums they can be delayed 12 to 18 hours.
- Liver signs can take 24 to 48 hours. Vets usually check blood sugar and liver values over a day or more.
- Do not make your dog vomit unless a vet or poison line tells you to. Merck notes activated charcoal does not bind xylitol well.
When you call, have your dog's weight, the product name and its ingredient list, how much is missing and when it happened. Phone numbers and fees were checked on the ASPCA and Pet Poison Helpline websites in October 2026.
Questions people ask
How much xylitol is toxic to a dog?
The Merck Veterinary Manual links doses above about 100 mg per kg of body weight (0.1 g/kg) to low blood sugar, and doses above 500 mg/kg (0.5 g/kg) to severe liver failure in some dogs. For a 20 lb (9 kg) dog that is about 0.9 g and 4.5 g of xylitol. Because labels rarely list the amount, treat any exposure as an emergency until a vet says otherwise.
How fast does xylitol poisoning start?
Signs of low blood sugar can start within 30 minutes, according to Merck. With some chewing gums absorption is slower and signs can be delayed 12 to 18 hours. Liver damage may not show for 24 to 48 hours, although blood tests can pick it up earlier.
What are the symptoms?
Low blood sugar causes vomiting, weakness, wobbliness, lethargy, collapse, seizures and coma. Liver injury causes lethargy, vomiting, yellow gums or eyes (jaundice) and bleeding problems. A dog can look normal at first, so do not wait for signs.
Is xylitol dangerous to cats?
Merck says dogs are the only domestic species in which xylitol poisoning has been reported, and that cats are not at risk of low blood sugar or liver injury from it. If your cat ate a product that also contains other ingredients, such as chocolate or medicine, call your vet about those.
Should I make my dog vomit?
Not on your own. Merck advises that vomiting should ideally be induced only under veterinary supervision and only in dogs that still seem normal, because a dog whose blood sugar drops can collapse or seize. Activated charcoal does not bind xylitol well and is not recommended.
Do the poison hotlines charge?
Pet Poison Helpline lists an $89 per-incident fee that includes follow-up calls. The ASPCA Animal Poison Control Center says a consultation fee may apply. Both answer 24 hours a day, every day. Your own vet or an emergency clinic is also a good first call.