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How Much Benadryl Can I Give My Dog Calculator?

Are you looking to give your dog some Benadryl (Diphenhydramine)? Wondering how much you should give and what’s a safe dosage? Well, my Benadryl calculator below will help you to find the appropriate dose.

Important Disclaimer: This calculator should be used for information purposes only. You should consult a vet ahead of administering any Benadryl to your dog. It is essential you confirm the dosages ahead of use.

Why Give Your Dog Benadryl

Dogs are often prescribe Diphenhydramine (which commonly goes by the name Benadryl) by vets for treatment of allergies (itching), motion sickness (to alleviate nausea) and to calm anxiety.

As such, it is often used for its anti-histamine purposes, along with another similar drug called Cetirizine.

How Much Benadryl Can I Give My Dog?

The amount of Benadryl you should give your dog will depend on a multitude of factors, namely their age, size, current diet, general health status, activity levels, hydration levels, among others.

This is why it is essential that you consult a vet before any administration.

That being said, a rough guide for reference is:

  • For every pound your dog weighs, they should be able to safely have 1mg of Benadryl.
  • So, a 25 lb. dog will need 25mg of Benadryl, a 50 lb. dog, 50mg etc.

It is also important to state that Benadryl tablets differ from liquid Benadryl – dosages will vary.

Equally, the typical Benadryl tablet will contain 25 mg.

Thus, you may need to cut up or divide these tablets depending on the size of your dog, or offer multiple tablets, for larger breeds.

Note: Benadryl overdose can be fatal. It is essential that you consult a vet to obtain the proper dosage ahead of time.

How Often Can I Give My Dog Benadryl?

You can administer an appropriate dose of Benadryl to your dog, 2-3 times per day (spread out evenly; or every 3-4 hours).

For instance, a 50mg dog could receive a 50mg dose of Benadryl in the morning, mid-afternoon and during the late evening [source].

How Long Does It Take For Benadryl To Work In Dogs?

It typically takes between 30 minutes and 1 hour for Benadryl to take affect in dogs. Though, time of day, the amount given, size of dog and hydration levels can all have an impact on this time.

Benadryl Side Effects In Dogs To Be Aware Of

Like any drug, inappropriate dosage, misuse or other factors can result in side effects in your dog.

Here are the main ones to be aware of:

  • Drowsiness,
  • Appetite changes
  • Constipation
  • Dry Mouth
  • Urination difficulties
  • Rapid breathing
  • Diarrhea/vomiting
  • Anxiety
  • Aggression

Should you suspect any of the above in relation or following giving Benadryl to your dog, consult a vet right way.

A Note On Liquid Benadryl

Liquid Benadryl is generally not safe to offer dogs, as most contain alcohol which is toxic to dogs.

Some liquid Benadryl products do not contain alcohol (typically those designed for children), and will need to be actively sought.

Liaising with a vet is again advised here, particularly if you intend on using liquid Benadryl.


For the most part, Benadryl is typically well-tolerated by dogs, where side ffects are rare and overdose is uncommon.

It is considered to be one of the safest over-the-counter drugs that veterinarians often prescribe for dogs.

That being said, if you do intend to give your dog Benadryl, don’t take any chances.

Consult a vet and administer it in accordance with their recommendations.

Related Questions

How much Benadryl can a 50 lb dog take?

A 50 lb dog can typically have 50mg of Benadryl at a time. Though consulting with a vet first for precise dosage for your dog is advised.

How many 25mg Benadryl can I give my 70 pound dog?

You can give your 70 pound dog 2.8 25mg Benadryl Tablets (for a total dose of 70mg). Though consulting with a vet first for precise dosage is advised.

How many Benadryl can you give an 80 pound dog?

You can give an 80 pound 80mg of Benadryl. Though consulting with a vet first for precise dosage for your dog is advised.

Is giving Benadryl to dogs harmful?

Giving Benadryl to a dog can be harmful if given in excess, or if the tablet/liquid of choice contains other harmful ingredients. Otherwise, Benadryl should be safe for a dog.