Why chocolate is toxic to dogs
Chocolate contains methylxanthines, mainly theobromine plus some caffeine. Dogs break these down slowly, so they build up and overstimulate the heart and nervous system. The darker and more bitter the chocolate, the more methylxanthines it contains.
Methylxanthine content by chocolate type
| Chocolate | mg per oz | mg per gram |
|---|---|---|
| White chocolate | 1.1 | 0.04 |
| Milk chocolate | 64 | 2.26 |
| Dark / semisweet chocolate (incl. chips) | 160 | 5.64 |
| Unsweetened baker's chocolate / 70%+ cacao | 440 | 15.52 |
| Dry cocoa powder | 807 | 28.47 |
| Cocoa bean hulls (mulch) | 255 | 8.99 |
Toxic dose thresholds
- About 20 mg/kg: mild signs such as vomiting, diarrhea and increased thirst.
- 40-50 mg/kg: heart effects (racing or irregular heartbeat).
- 60 mg/kg or more: seizures.
How much chocolate reaches the 20 mg/kg threshold?
This table shows the approximate amount of each chocolate that delivers 20 mg/kg, the level where mild signs can begin. Treat amounts above these as needing a vet call immediately.
| Dog weight | Milk chocolate | Dark / semisweet | Baker's | Cocoa powder |
|---|---|---|---|---|
| 5 lb | 0.71 oz (20 g) | 0.28 oz (8 g) | 0.1 oz (3 g) | 0.06 oz (2 g) |
| 10 lb | 1.42 oz (40 g) | 0.57 oz (16 g) | 0.21 oz (6 g) | 0.11 oz (3 g) |
| 20 lb | 2.83 oz (80 g) | 1.13 oz (32 g) | 0.41 oz (12 g) | 0.22 oz (6 g) |
| 40 lb | 5.67 oz (161 g) | 2.27 oz (64 g) | 0.82 oz (23 g) | 0.45 oz (13 g) |
| 60 lb | 8.5 oz (241 g) | 3.4 oz (96 g) | 1.24 oz (35 g) | 0.67 oz (19 g) |
| 80 lb | 11.34 oz (321 g) | 4.54 oz (129 g) | 1.65 oz (47 g) | 0.9 oz (25 g) |
Symptoms of chocolate poisoning
Signs usually appear within 6-12 hours and can last up to 72 hours: vomiting, diarrhea, thirst and urination, restlessness, panting, a racing heart, tremors and, in severe cases, seizures. Fat and sugar in chocolate can also trigger pancreatitis a few days later.
What to do if your dog ate chocolate
- Work out the type and amount (check wrappers) and your dog's weight.
- Call your vet or animal poison control right away, even if your dog seems fine.
- Do not induce vomiting at home unless a vet tells you to and explains how.
- Early treatment (induced vomiting, activated charcoal, fluids, heart monitoring) is most effective.
Also see: Can dogs eat chocolate? and macadamia nuts, which are often combined with chocolate in cookies.
Frequently asked questions
How much chocolate can kill a dog?
Severe and potentially fatal effects are associated with doses of 60 mg/kg and above. For a 20 lb dog that is about 1.2 oz of baker's chocolate or about 3.4 oz of semisweet dark chocolate. Much smaller amounts can still make a dog ill.
My dog ate one chocolate chip cookie. Is that dangerous?
For most medium and large dogs one cookie is a low dose, but small dogs and dark-chocolate cookies are higher risk. Use the calculator and call your vet for advice.
How long does chocolate poisoning last?
Signs often start within 6-12 hours and can last up to 72 hours because theobromine is cleared slowly.
Is milk chocolate safe for big dogs?
It is less dangerous than dark chocolate, but larger amounts can still cause symptoms and pancreatitis. No chocolate is safe to feed.