Most people know that chocolate is toxic to dogs but do you know why? 

Chocolate contains theobromine, a compound that is a heart stimulant, diuretic and is used in medicine as a

vasodilator. Symptoms include excitability, hyperactivity, muscle twitches, excessive panting, vomiting and

diarrhea. Because of the diuretic effect, your dog may pass large volumes of urine and be unusually thirsty.  Theobromine can increase the dog’s heart rate, increase blood pressure, and cause the heart to beat irregularly. In severe cases, seizures can occur.

How much chocolate will hurt my dog? That depends on the type of chocolate and the amount of theobromine it contains.

  • White chocolate has 1mg theobromine per ounce.
  • Milk chocolate has 60 mg per ounce.
  • Semi‐sweet chocolate has 260mg per ounce.
  • Baking chocolate or unsweetened chocolate has a whopping 450mg per ounce
  • Dry cocoa powder has 800mg per ounce.

Below is a quick reference of harmful levels:

Dog’s weight            Amount of milk chocolate   Amount of baking chocolate     Appr. Mg of theobromin

5 lb.                       4 oz.                              0.5 oz.                                 200

10 lbs.                    8 oz.                              1.0 oz.                                 400

20 lbs.                    1 lb.                               2.5 oz.                                 900

30 lbs.                    2 lbs.                             3.25 oz.                                1300

40 lbs.                    2.5 lbs.                           4.5 oz.                                 1800

50 lbs.                    3 lbs.                             5.5 oz.                                  2250

60 lbs.                    4 lbs.                             7.0 oz.                                  2700

70 lbs.                    5 lbs.                             8.5 oz.                                  3400

Although white chocolate only has 1mg of theobromine per ounce it is mostly sugar and cocoa butter.  So it is best to avoid white chocolate as well.