Correct Benadryl Dosage for Dogs

allergy-ultratabsBenadryl is a must in our dog emergency preparedness kit.  The antihistamine can help everything from grass allergies to bee stings.  But did you know that the main ingredient is extremely toxic if the pup is not given the correct dose?  Sometimes it can be difficult to know exactly how much is the right amount and if we give our dogs too much, the results can be catastrophic

Just how catastrophic is exactly what a recent study from North Carolina State endeavored to find. They measured the level of exposure in 621 cases between 2008-2013 to identify exactly how much Diphenhydramine(active Benadryl ingredient) would represent a toxic dosage. The researchers used the Animal Poison Control database from January 2008- December 2013 to identify dogs that had been reported as poisoned by Benadryl.

The Good News

The authors found that most dogs exposed to up to 4x the recommended dose of Benadryl(2.2mg/kg) did not develop any clinical symptoms of poisoning.  The normal adult dose per pill in Benadryl is 25mg Diphenhydramine so, in most medium and large breeds, it becomes less and less likely that a dog will develop symptoms.  For example, Sully is 84lbs which works out to 14 adult Benadryl pills to reach the 4x recommended dose threshold.

The Bad News

As the sampled cases started to approach 6x the recommended dosage, the researchers found that the dogs began to exhibit a range of symptoms associated with poisoning.  Many of which were the heart and central nervous system related.  As the severity of the symptoms increased there was a shift from CNS depression to excitation.  Unfortunately, there were also 3 dogs that succumbed to their poisoning and died.


  • We recommend the same level of attention be paid to potential dog poisons and potential human poisons.  Lock them away, out of reach, to minimize the chance of an accident happening( we all know that dogs are experts at getting into things they shouldn’t).
  • Teach a bomb-proof leave it command.  It could save your dog’s life.
  • If you have a small-breed dog, be sure that you are extremely vigilant when giving your dog Benadryl.  Small breeds made up a very large percentage of the cases that were used in this study. We recommend using the 12.5 mg liquid for any dog under 25 lbs.
  • Use the calculator below! It will give you the exact recommended dose for your dog by bodyweight.
  • Finally, in the event that your dog ingests an unknown quantity of Benadryl, don’t wait, call your vet immediately and take your pup there ASAP.