Why Chocolate Is Toxic to Dogs
Chocolate contains theobromine and caffeine, both methylxanthine compounds that dogs metabolize far more slowly than humans. In humans, the half-life of theobromine is about 2-3 hours. In dogs, it is 17.5 hours. This means the compound accumulates in a dog's system much longer, allowing even moderate amounts of certain chocolate types to reach toxic concentrations.
Theobromine Content by Chocolate Type
- Baking/unsweetened chocolate: 390-450 mg theobromine per ounce. The most dangerous type by weight.
- Dark chocolate (70%+ cocoa): 150-170 mg/oz
- Semi-sweet chocolate chips: 130-150 mg/oz
- Milk chocolate: 44-64 mg/oz
- White chocolate: 0.25 mg/oz (negligible theobromine)
Toxic Dose Thresholds
- 20 mg/kg: Mild signs begin: vomiting, diarrhea, increased urination, restlessness
- 40 mg/kg: Moderate signs: muscle tremors, hyperactivity, rapid heart rate, elevated blood pressure
- 60 mg/kg: Severe signs: seizures, cardiac arrhythmia, hyperthermia
- 100 mg/kg: Potentially lethal dose
A 10 lb (4.5 kg) dog eating just 0.5 oz of baking chocolate reaches a dose of approximately 44 mg/kg, putting it in the moderate-to-severe range.
Symptoms and Timeline
Symptoms typically appear within 6-12 hours of ingestion and can last 24-72 hours because of the long half-life of theobromine. Early signs are gastrointestinal: vomiting, diarrhea, and increased thirst. Later signs at higher doses include muscle tremors, uncoordinated movement, rapid breathing, and in severe cases, heart rhythm abnormalities.
What to Do If Your Dog Ate Chocolate
Contact the ASPCA Animal Poison Control Center (888-426-4435) or your veterinarian immediately after any ingestion of dark or baking chocolate by a small dog, or any potentially significant quantity by a larger dog. Do not wait for symptoms to appear. If ingestion occurred within 2 hours, your vet may recommend inducing vomiting. Activated charcoal may be administered to reduce absorption.
White Chocolate and Cocoa Powder
White chocolate contains negligible theobromine and is not a theobromine toxicity risk. However, the high fat and sugar content can trigger pancreatitis and gastrointestinal distress. Cocoa powder is among the most concentrated sources of theobromine (800-1,500 mg/oz) and is extremely dangerous even in small quantities.