As Amazon Associates, we may earn from qualifying purchases. See disclosure in sidebar.

Lethal Dose of Benadryl for Dogs

Score for Seniors:
Activity Level:
Weight: Pounds


On top of the emotional stress following illness and vet treatments, a lot of dog owners also face expensive vet bills. As a result, many owners are trying to find inexpensive options to euthanize their dogs, and want to figure out how to euthanize a dog with a simple over-the counter product such as Benadryl, and what to find out what the lethal dose of Benadryl is for dogs.

While Benadryl can indeed be lethal to dogs, there are several very important legal and medical factors that you should consider. 

Lethal Dose for Dogs

According to this scientific paper, the lethal dose for diphenhydramine in dogs ranges between 24 to 30 mg per kilogram of body weight by IV administration. For a 40-pound dog, this would equate to about 430 to 540 mg, or 9-10 tablets (for tablets with 50mg diphenhydramine – note that some tablets are 25mg only).

However, it is important to note that this study was very limited in scope, and estimates are derived from extrapolated values from other species. What do we take from this? The lethal dose of Benadryl for dogs is still largely unknown.

Critical Considerations for Putting Your Dog to Sleep

Most importantly – there are critical reasons why Benadryl should NOT be used to put your dog to sleep, including:

  1. Benadryl will create unnecessary suffering for your dog.
    Benadryl can have dramatic side effects for your dog, they can suffer a lot before the active ingredient actually results in death. These are significant effects that could cause unnecessary pain and suffering for your dog. Benadryl is lethal to dogs because it can cause serious neurological and cardiovascular effects, with effects including hyper-excitability, rapid heartbeat, seizures, convulsions, or respiratory failure. This will result in a very painful death for your dog. There are much more humane ways to euthanize your dog.
  2. Most vets will ensure that your dogs are sedated prior to euthanasia, creating a pain-free experience.
    Your veterinarian will make sure that your dog is sedated and will not experience any pain prior to receiving the euthanasia medication.
  3. Most US states require that a veteriary professional is involved. Dog euthanasia in the US is highly regulated and can often ONLY be performed by a veterinarian professional or euthanasia technician to ensure a pain-free and effective process for the animals

Learn more:


  • Jason is a pet specialized writer who works with our veterinarian team ( to write in-depth articles about pet health and behaviors.

How useful is this page?

Help us improve. Click on a star to rate it:

Average rating 1 / 5. Vote count: 1

Disclaimer: This website's content is not meant to be a substitute for veterinary care, diagnosis, or treatment. Always consult with your veterinarian to determine the best course of action. Read More.

Be the first to comment

Leave a Reply

Your email address will not be published.


This site uses Akismet to reduce spam. Learn how your comment data is processed.