Skip to main content
PetDosageChart

Antihistamine · For Dogs

How much Benadryl (Diphenhydramine) can I give my dog?

Standard Benadryl dose for dogs is 2 mg per kg (0.91 mg per lb), given every 8-12 hours. Use the calculator below for your dog's exact weight, or jump to the weight-by-weight chart.

Onset
30-60 minutes
Duration
8-12 hours
Class
Antihistamine

Calculator estimate from Plumb’s Veterinary Drug Handbook. Not yet vet-reviewed — see our methodology .

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. Sourced from Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

Last reviewed by the PetDosageChart editorial team on . How we review

Dosage Calculator · 01

Enter your dog's weight

By Weight

Benadryl dose by dog weight

Pick your dog's weight to jump to a dedicated page with the dose, frequency, safety notes, and FAQ for that size.

Embed this calculator on your site

Get a free Benadryl dosage widget

Get embed code

Free forever. Works in any blog post or article. Adds a small "Powered by petdosagechart.com" credit at the bottom.

Dosage Chart · 02

Benadryl dosage for dogs by weight

Scroll sideways to see full table

Weight Low Dose Standard Max Safe 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

Common Uses · 03

What is Benadryl (Diphenhydramine) used for in dogs?

allergies itching motion sickness mild anxiety insect stings

Administration · 04

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 · 05

Side effects of Benadryl in dogs

Common side effects

drowsiness
dry mouth
urinary retention
decreased appetite

Serious side effects — call your vet

  • rapid heartbeat
  • difficulty breathing
  • seizures
  • severe lethargy

Emergency · 06

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

For Cats

Looking for Benadryl dosage for cats?

View the Benadryl dosage chart and calculator for cats.

Related · 08

Related medications for dogs

Sources · 09

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.

Read more about our methodology and how we calculate dosages.

Transparency · 11

How this page was made

Sourced from Plumb's Veterinary Drug Handbook, the reference used in US vet schools. Every dose, frequency, and tablet count on this page is generated from that data, then checked against the published references below.

Sources cited
  • Plumb's Veterinary Drug Handbook
  • Merck Veterinary Manual
Calculator formula
Doses scale linearly from a standard basis of 2 mg per kg (0.91 mg per lb) of body weight, given every 8-12 hours. The calculator multiplies that basis by your dog's weight and rounds to the closest available tablet size.
Last-reviewed status
Automated from Plumb’s, not yet vet-reviewed.

More on our methodology and editorial process — how we source, calculate, and review dogs dosage data.

Frequently Asked · 07

Questions about this medication

How much Benadryl can I give my dog by weight?
The standard Benadryl (diphenhydramine) dose for dogs is 1 mg per pound of body weight (2 mg/kg) every 8-12 hours. As a chart: 10 lb dog → 10 mg; 25 lb dog → 25 mg; 50 lb dog → 50 mg; 75 lb dog → 75 mg; 100 lb dog → 100 mg per dose. Always use plain diphenhydramine — never combination products containing decongestants, acetaminophen, or xylitol.
How much Benadryl to give a 10 lb dog?
A 10 lb dog should receive about 10 mg of Benadryl per dose, which is approximately half of a 25 mg tablet. Give every 8-12 hours, up to three times daily. Use plain diphenhydramine only.
How much Benadryl to give a 25 lb dog?
A 25 lb dog should receive about 25 mg of Benadryl per dose — one full 25 mg tablet of plain diphenhydramine. Give every 8-12 hours, up to three times in 24 hours.
How much Benadryl to give a 50 lb dog?
A 50 lb dog should receive about 50 mg of Benadryl per dose — either one 50 mg tablet or two 25 mg tablets. Give every 8-12 hours, up to three times daily. Always use plain diphenhydramine and verify the label is free of xylitol or other added ingredients.
How much Benadryl to give a 75 lb dog?
A 75 lb dog should receive about 75 mg of Benadryl per dose, given every 8-12 hours. The easiest way to dose is to give one 50 mg tablet plus one 25 mg tablet of plain diphenhydramine.
How much Benadryl to give a 100 lb dog?
A 100 lb dog should receive about 100 mg of Benadryl per dose, which is two 50 mg tablets of plain diphenhydramine. Give every 8-12 hours, up to three times daily. Confirm the dose with your vet before exceeding 100 mg per dose.
How often can I give my dog Benadryl?
Benadryl can be given every 8-12 hours, up to three times in a 24-hour period. The medication takes effect in 30-60 minutes and lasts 8-12 hours, so consistent timing matters more than maximum frequency. Do not exceed 3 doses per day without veterinary approval.
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.
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.
How often can I give my dog Benadryl in 24 hours?
Benadryl can be given every 8-12 hours, which works out to 2-3 doses in a 24-hour period. Do not exceed 3 doses per day. The drug takes 30-60 minutes to start working and lasts 8-12 hours, so spacing matters more than maximum frequency.
How long can I keep giving my dog Benadryl?
For short-term issues (a bee sting, motion sickness, a single allergic reaction) Benadryl is typically given for 1-3 days. For ongoing seasonal allergies, daily use should be supervised by a veterinarian. If symptoms persist beyond 5-7 days, call your vet rather than continuing to dose at home.
How much Benadryl for a 5 lb dog?
A 5 lb dog should receive about 5 mg of Benadryl per dose. Standard 25 mg adult tablets are too large; use a 12.5 mg children's chewable cut in half, or measure liquid diphenhydramine that is verified xylitol-free. Give every 8-12 hours.
How much Benadryl for a 15 lb dog?
A 15 lb dog should receive about 15 mg of Benadryl per dose. The easiest way is half of a 25 mg tablet (12.5 mg, slightly low) or 1.5 chewable tablets of 12.5 mg children's diphenhydramine. Give every 8-12 hours.
How much Benadryl for a 20 lb dog?
A 20 lb dog should receive about 20 mg of Benadryl per dose. The closest standard tablet is one 25 mg adult tablet (slightly above target, but within the safe range). Give every 8-12 hours, up to 3 times daily.
How much Benadryl for a 30 lb dog?
A 30 lb dog should receive about 30 mg of Benadryl per dose. Use one 25 mg tablet plus a quarter of a second 25 mg tablet, or simply round up to a single 50 mg tablet only if your dog is on the higher end of the 25-35 lb range. Give every 8-12 hours.
How much Benadryl for a 40 lb dog?
A 40 lb dog should receive about 40 mg of Benadryl per dose. The simplest approach is one 50 mg tablet (slightly above target, within safe range) or one and a half 25 mg tablets (37.5 mg). Give every 8-12 hours.
How much Benadryl for a 60 lb dog?
A 60 lb dog should receive about 60 mg of Benadryl per dose. The easiest tablet combination is one 50 mg tablet plus a half-tablet of 25 mg (total 62.5 mg). Give every 8-12 hours, up to 3 times daily.
How much Benadryl for a 70 lb dog?
A 70 lb dog should receive about 70 mg of Benadryl per dose. Use one 50 mg tablet plus one 25 mg tablet (total 75 mg, within safe range). Give every 8-12 hours.
How much Benadryl for an 80 lb dog?
An 80 lb dog should receive about 80 mg of Benadryl per dose. The cleanest combination is one 50 mg tablet plus one 25 mg tablet (75 mg) or three 25 mg tablets (75 mg). Give every 8-12 hours.
How much Benadryl for a 90 lb dog?
A 90 lb dog should receive about 90 mg of Benadryl per dose. Use one 50 mg tablet plus one 25 mg tablet plus half of a third 25 mg tablet (87.5 mg) or two 50 mg tablets (100 mg, on the higher end of safe). Give every 8-12 hours.
How much Benadryl can I give my puppy?
Puppies under 6 months should generally not receive Benadryl without veterinary approval. For puppies over 6 months, use 1 mg per pound of body weight every 8-12 hours, the same as adult dogs — but always call your vet first for any puppy under 1 year.

Safety · 10

More resources