Benadryl dose for dogs
The usual dose of diphenhydramine for dogs is 1 mg per pound of body weight (about 2.2 mg/kg), given every 8-12 hours, up to three times a day. The Merck Veterinary Manual lists a range of 2-4 mg/kg every 8-12 hours, so your vet may prescribe a different dose for your dog's situation.
Benadryl dosage chart for dogs by weight
Doses below use 1 mg per lb, rounded to the nearest quarter tablet. Children's liquid is 12.5 mg per 5 mL.
| Dog weight | Dose (mg) | 25 mg tablets | Children's liquid |
|---|---|---|---|
| 5 lb (2.3 kg) | 5 mg | ¼ | 2 mL |
| 10 lb (4.5 kg) | 10 mg | ½ | 4 mL |
| 15 lb (6.8 kg) | 15 mg | ½ | 6 mL |
| 20 lb (9.1 kg) | 20 mg | ¾ | 8 mL |
| 25 lb (11.3 kg) | 25 mg | 1 | 10 mL |
| 30 lb (13.6 kg) | 30 mg | 1¼ | 12 mL |
| 40 lb (18.1 kg) | 40 mg | 1½ | 16 mL |
| 50 lb (22.7 kg) | 50 mg | 2 | 20 mL |
| 60 lb (27.2 kg) | 60 mg | 2½ | 24 mL |
| 70 lb (31.8 kg) | 70 mg | 2¾ | 28 mL |
| 80 lb (36.3 kg) | 80 mg | 3¼ | 32 mL |
| 100 lb (45.4 kg) | 100 mg | 4 | 40 mL |
For dogs under 10 lb, liquid or a vet-prescribed dose is easier to measure accurately than splitting tablets.
Which Benadryl is safe for dogs?
- Use only plain diphenhydramine. Check that diphenhydramine HCl is the only active ingredient on the label.
- Never use combination products such as "Benadryl-D", "Allergy Plus Congestion" or "Allergy & Sinus". They contain decongestants (pseudoephedrine or phenylephrine) or pain relievers (acetaminophen) that can poison dogs.
- Check liquids and chewables for xylitol, a sweetener that is highly toxic to dogs, and avoid liquids containing alcohol.
- Outside the US, "Benadryl" may be a different drug. In the UK, for example, Benadryl Allergy products contain acrivastine or cetirizine, not diphenhydramine. Do not use the dose on this page for those products.
What vets use Benadryl for in dogs
- Mild allergic reactions, itching and hives
- Insect bites and bee stings (mild swelling)
- Before vaccines in dogs with a history of reactions (as directed by a vet)
- Motion sickness and mild travel anxiety (its sedating effect varies between dogs)
Benadryl is not a treatment for anaphylaxis. If your dog has trouble breathing, a swollen face or throat, pale gums, vomiting or collapse after a sting or vaccine, go to an emergency vet immediately.
Side effects
The most common side effect is drowsiness. Others include dry mouth, urinary retention, faster heart rate and, in some dogs, the opposite effect: excitement or agitation. Signs usually start within 30 minutes and last 8-12 hours.
When not to give Benadryl
Talk to your vet first if your dog has glaucoma, heart disease, high blood pressure, an overactive thyroid, prostate enlargement or trouble urinating, seizures, or is pregnant or nursing, or if your dog takes other sedatives or medicines.
Benadryl overdose in dogs
Signs of an overdose include severe agitation or sedation, a racing heart, high body temperature, dilated pupils, tremors and seizures. If you think your dog got too much, call your vet or animal poison control: ASPCA Animal Poison Control: (888) 426-4435 · Pet Poison Helpline: (855) 764-7661.
Frequently asked questions
How much Benadryl can I give my dog?
The usual dose is 1 mg per pound of body weight, every 8-12 hours. For example, a 25 lb dog gets 25 mg (one standard tablet). Ask your vet first.
How much Benadryl can I give a 50 lb dog?
About 50 mg, which is two 25 mg tablets, every 8-12 hours, if your vet agrees.
How long does Benadryl take to work in dogs?
Usually about 30 minutes, with effects lasting roughly 8-12 hours.
Can I give my dog children's Benadryl?
Yes, if diphenhydramine is the only active ingredient and it contains no xylitol. Children's liquid is 12.5 mg per 5 mL, so a 10 lb dog would need about 4 mL.
Can Benadryl help my dog sleep or calm down?
It makes some dogs drowsy, but the effect is unpredictable and some dogs become excited. Ask your vet about safer, more reliable options for anxiety.
Is Benadryl safe for cats?
Vets sometimes prescribe diphenhydramine for cats, but cats often drool and react badly to the taste. Do not give it without your vet's dose.