We’ve all heard it, ”Don’t give your dog chocolate it will kill him”. Well how true is it you’re probably wondering. Do I have to rush him to an emergency vet if he ate one of my M&M’s?

The truth is chocolate contains theobromine that is toxic to dogs in sufficient quantities. This is a xanthine compound in the same family of caffeine, and theophylline.

Toxic Levels

The good news is that it takes, on average, a fairly large amount of theobromine 100-150 mg/kg to cause a toxic reaction. Although there are variables to consider like the individual sensitivity, animal size and chocolate concentration.

On average,
Milk chocolate contains 44 mg of theobromine per oz.
Semisweet chocolate contains 150mg/oz.
Baker’s chocolate 390mg/oz.

Using a dose of 100 mg/kg as the toxic dose it comes out roughly as:
1 ounce per 1 pound of body weight for Milk chocolate
1 ounce per 3 pounds of body weight for Semisweet chocolate
1 ounce per 9 pounds of body weight for Baker’s chocolate.

So, for example, 2 oz. of Baker’s chocolate can cause great risk to an 15 lb. dog. Yet, 2 oz. of Milk chocolate usually will only cause digestive problems. 

Clinical Signs

Xanthines affect the nervous system, cardiovascular system and peripheral nerves. It has a diuretic effect as well. Clinical signs: 

Hyper excitability 
Hyper irritability 
Increased heart rate 
Restlessness 
Increased urination 
Muscle tremors 
Vomiting 
Diarrhea