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PetDosageChart

Benadryl (Diphenhydramine) Dosage for Dogs

Antihistamine ⏱ Onset: 30-60 minutes ⏳ Duration: 8-12 hours

This dosage information is for educational purposes only. Always consult your veterinarian before giving any medication to your pet. Dosages may vary based on your pet's health conditions, other medications, and individual factors.

Content reviewed by licensed veterinarians. This information is sourced from veterinary drug references including Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

Dosage Calculator

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Benadryl Dosage Chart for Dogs by Weight

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Weight Low Dose Standard Dose Max Dose Frequency
5 lbs (2.3 kg) 2.5mg 4.5mg 9mg every 8-12 hours
10 lbs (4.5 kg) 4.5mg 9mg 18mg every 8-12 hours
15 lbs (6.8 kg) 7mg 13.5mg 27mg (25mg tablet) every 8-12 hours
20 lbs (9.1 kg) 9mg 18mg 36.5mg every 8-12 hours
25 lbs (11.3 kg) 11.5mg 22.5mg (25mg tablet) 45mg (2 × 25mg) every 8-12 hours
30 lbs (13.6 kg) 13.5mg 27mg (25mg tablet) 54.5mg (2 × 25mg) every 8-12 hours
40 lbs (18.1 kg) 18mg 36mg 72.5mg (3 × 25mg) every 8-12 hours
50 lbs (22.7 kg) 22.5mg (25mg tablet) 45.5mg (2 × 25mg) 91mg every 8-12 hours
60 lbs (27.2 kg) 27mg (25mg tablet) 54.5mg (2 × 25mg) 109mg every 8-12 hours
70 lbs (31.7 kg) 31.5mg 63.5mg 127mg (5 × 25mg) every 8-12 hours
80 lbs (36.3 kg) 36.5mg 72.5mg (3 × 25mg) 145mg (6 × 25mg) every 8-12 hours
90 lbs (40.8 kg) 41mg 81.5mg 163mg every 8-12 hours
100 lbs (45.4 kg) 45.5mg (2 × 25mg) 91mg 181.5mg every 8-12 hours
120 lbs (54.4 kg) 54.5mg (2 × 25mg) 109mg 217.5mg every 8-12 hours
150 lbs (68 kg) 68mg 136mg 272mg (11 × 25mg) every 8-12 hours

What is Benadryl (Diphenhydramine) used for in dogs?

allergies itching motion sickness mild anxiety insect stings

How to give Benadryl to your dog

Give Benadryl with food to reduce stomach upset. Use plain diphenhydramine only — avoid formulations containing decongestants (pseudoephedrine) or pain relievers (acetaminophen), which are toxic to dogs. Liquid formulations may contain xylitol, which is extremely dangerous for dogs.

Available Forms

tablet, capsule, liquid

Give with Food?

Yes — give with food

Side effects of Benadryl in dogs

Common side effects

drowsiness
dry mouth
urinary retention
decreased appetite

Serious side effects

  • rapid heartbeat
  • difficulty breathing
  • seizures
  • severe lethargy

When to call the vet

Call your vet immediately if your dog shows any of these signs:

  • Vomiting or diarrhea after taking
  • Signs of allergic reaction (facial swelling, hives)
  • Extreme lethargy or unresponsiveness
  • Seizures or tremors
  • Difficulty breathing

Related Medications for Dogs

Antihistamine (second-generation)

Zyrtec

Cetirizine

For allergies

View dosage chart
Antihistamine (second-generation)

Claritin

Loratadine

For allergies

View dosage chart
Antihistamine (first-generation)

Atarax

Hydroxyzine

For allergies

View dosage chart
First-generation antihistamine

Chlor-Trimeton

Chlorpheniramine

For Allergies

View dosage chart

Sources & References

The dosage information on this page is compiled from the following veterinary and pharmaceutical references:

  • Plumb's Veterinary Drug Handbook — the standard veterinary pharmacology reference used by veterinarians worldwide.
  • Merck Veterinary Manual — a trusted, peer-reviewed resource for veterinary professionals and pet owners.
  • DailyMed (FDA Drug Labels) — official FDA-approved drug labeling and prescribing information for Diphenhydramine.

Frequently Asked Questions

Can I give my dog Benadryl every day?
Yes, Benadryl can be given to dogs daily for ongoing allergy management, but only under veterinary guidance. Long-term daily use should be monitored by your vet to ensure there are no adverse effects on your dog's liver or kidneys.
How much Benadryl can I give my dog?
The standard dose is 2 mg per kilogram (about 1 mg per pound) of body weight, given 2-3 times daily. For example, a 25 lb (11 kg) dog would typically receive one 25 mg tablet. Always use plain diphenhydramine and never exceed the maximum daily dose without veterinary approval.
Can Benadryl kill a dog?
While Benadryl is generally safe for dogs at recommended doses, a significant overdose can be dangerous or fatal. Signs of overdose include rapid heartbeat, dilated pupils, agitation, seizures, and respiratory depression. If you suspect an overdose, contact your veterinarian or an emergency animal poison control hotline immediately.
How long does Benadryl last in dogs?
Benadryl typically lasts 8-12 hours in dogs. It begins working within 30-60 minutes of administration. Most veterinarians recommend dosing every 8-12 hours (2-3 times daily) for consistent relief.
Can I give my dog liquid Benadryl?
You can give liquid Benadryl, but you must check the ingredients carefully. Many liquid formulations made for children contain xylitol, an artificial sweetener that is extremely toxic to dogs. Always choose a xylitol-free liquid or use tablets instead.

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