How much chocolate is toxic to dogs?

The theobromine dose that matters

The toxic threshold for theobromine in dogs is typically quoted at 100 to 200mg per kilogram of body weight, with effects beginning to appear at lower doses and severe toxicity at higher ones. The dose your dog received depends on both the chocolate type and the quantity eaten. Baking chocolate delivers around 450mg of theobromine per ounce. Dark chocolate (70 percent cocoa) delivers around 170mg per ounce. Milk chocolate delivers around 50mg per ounce. To convert: multiply the weight of chocolate in grams by the milligrams per gram for that type, then divide by the dog's body weight in kilograms.

A practical reference table

For a 5kg dog, around 12g of dark chocolate or 120g of milk chocolate may cause effects. For a 10kg dog, around 25g of dark chocolate or 250g of milk chocolate. For a 20kg dog, around 50g of dark chocolate or 500g of milk chocolate. These are approximate thresholds for the onset of effects. Severe toxicity occurs at higher doses. These numbers assume 70 percent dark chocolate and standard milk chocolate. Do not use this to decide whether to call a vet: call the vet and give them the exact numbers.

Why you cannot assess this yourself

The variables are too many. The cocoa percentage affects theobromine content significantly within the dark chocolate category. The dog's individual metabolism, age and health status affect how quickly theobromine is processed. Whether the dog ate on a full or empty stomach affects absorption rate. The number you are working with is an approximation of an approximation. A vet uses established toxicity models and may recommend treatment even when the calculated dose is below the theoretical threshold, because the consequences of under-treating are severe.

When there is no emergency

If your 30kg Labrador ate one square of milk chocolate, the theobromine dose is likely not a clinical emergency. Your vet will tell you that. The point is not that every chocolate incident is a crisis; the point is that you should make the phone call and get that confirmation rather than making the judgment yourself. The call takes three minutes. The consequences of being wrong take considerably longer to resolve.