How much Benadryl can I give my dog?
The dose most vets use for plain Benadryl (diphenhydramine) is 1 mg per pound of body weight, two to three times a day (about 2.2 mg per kg). The Merck Veterinary Manual lists a range of 2 to 4 mg per kg, and your vet may choose a different dose for your dog.
25 mg tablets = dose ÷ 25
Children's liquid (12.5 mg / 5 mL) = dose ÷ 2.5 mL
Benadryl dosage chart for dogs
| Dog's weight | Dose | 25 mg tablets | Children's liquid |
|---|---|---|---|
| 10 lb | 10 mg | a bit under ½ | 4 mL |
| 20 lb | 20 mg | ¾ | 8 mL |
| 25 lb | 25 mg | 1 | 10 mL |
| 40 lb | 40 mg | 1½ | 16 mL |
| 50 lb | 50 mg | 2 | 20 mL |
| 75 lb | 75 mg | 3 | 30 mL |
| 100 lb | 100 mg | 4 | 40 mL |
For small dogs the liquid or chewables make it easier to give the right amount. Tablets can be split along the score line.
Safety checklist
- Plain diphenhydramine only. Products with pseudoephedrine or phenylephrine (the "D" versions) or with acetaminophen can be very dangerous for dogs.
- Read the liquid's label. Choose a children's liquid without alcohol and without xylitol.
- Ask your vet first if your dog has glaucoma, heart disease, high blood pressure, seizures, thyroid or prostate problems, is pregnant or nursing, or takes other medicine.
- Common side effects: sleepiness, dry mouth, and sometimes the opposite (excitement). Rare: fast breathing or heartbeat. Signs of overdose include agitation, dilated pupils and a racing heart: call a vet.
What vets use it for
Benadryl is an antihistamine. Vets sometimes suggest it for mild allergy signs such as itching, hives or a mild insect sting, and occasionally for motion sickness. It does not work well for long-term skin allergies, and it is not a treatment for anaphylaxis: swelling of the face or throat, or trouble breathing, needs a vet right away.
Not sure your dog's weight is current? Weigh yourself holding the dog, then subtract your own weight. For other safety questions, see the can dogs eat it checker.
Sources: Merck Veterinary Manual, antihistamines (diphenhydramine 2-4 mg/kg); American Kennel Club and PetMD guidance (1 mg/lb, every 8-12 hours). This page is general information, not a prescription.
Frequently asked questions
How much Benadryl can I give my dog?
The usual dose is 1 mg of diphenhydramine per pound of body weight, given 2 to 3 times a day. A 25 lb dog gets about 25 mg, which is one standard tablet. Ask your vet before the first dose.
How many Benadryl tablets can I give a 50 lb dog?
About 50 mg, which is two 25 mg tablets, up to 3 times a day.
Can I give my dog children's Benadryl liquid?
Yes, if it contains only diphenhydramine and no alcohol or xylitol. Children's liquid has 12.5 mg in 5 mL, so a 20 lb dog would get about 8 mL.
How long does Benadryl take to work in dogs?
Usually about 30 minutes to an hour, and the effect lasts around 8 to 12 hours.
Can a dog overdose on Benadryl?
Yes. Too much can cause agitation, a racing heart, fast breathing and seizures. If you think your dog got too much, call your vet or a pet poison hotline right away.
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Last updated October 2026.