Chocolate is poisonous to dogs; however, the danger of chocolate to your dog depends on the type of chocolate, the amount consumed and your dog’s size. In large enough quantities, chocolate can be lethal to your dog. As you would expect, larger dogs can consume more chocolate than smaller dogs before suffering any ill effects. A small amount of chocolate will probably only give your dog an upset stomach with vomiting or diarrhea. With large amounts, can produce muscle tremors, seizures, an irregular heartbeat, internal bleeding or a heart attack.