Safe dosage in mg, tablets, and liquid — calculated by your dog's weight, age, and symptom type. Always confirm with your vet.
Benadryl (diphenhydramine) is one of the most commonly used over-the-counter medications for dogs — for allergic reactions, bee stings, hives, motion sickness, and mild anxiety. The dosing principle is simple: 1mg per pound of body weight, up to a maximum of 50mg per dose.
This calculator gives you the exact dose in milligrams, number of standard 25mg tablets, and liquid dosing volume — along with the next safe dose timing, and specific cautions for your dog's situation.
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Diphenhydramine (the active ingredient in Benadryl) is one of the few human medications that veterinarians commonly recommend for home use in dogs. It works by blocking histamine receptors, reducing allergic symptoms including itching, hives, swelling, and runny eyes.
| Dog Weight | Dose (mg) | Standard Tablets (25mg) | Children's Liquid (12.5mg/5ml) |
|---|---|---|---|
| Under 10 lbs | 5–10mg | ¼ tablet | 2–4 ml |
| 10–25 lbs | 10–25mg | ½–1 tablet | 4–10 ml |
| 25–50 lbs | 25–50mg | 1–2 tablets | 10–20 ml |
| 50–75 lbs | 50mg (max) | 2 tablets | 20 ml |
| Over 75 lbs | 50mg (max) | 2 tablets | 20 ml |
This is the most dangerous mistake pet owners make. Never give your dog: Benadryl-D (contains pseudoephedrine, which is toxic), any Benadryl formula with "decongestant," any liquid formula containing xylitol (a sweetener toxic to dogs — check all ingredients), combination products with pain relievers (acetaminophen is toxic to dogs), or any "non-drowsy" formula (these often contain different active ingredients). Stick to plain diphenhydramine only and verify the ingredients label every time.
Dogs with glaucoma, enlarged prostate, or cardiovascular disease should not receive diphenhydramine — it can worsen these conditions. Dogs on MAOIs, amitraz, or other antihistamines should not receive Benadryl without veterinary guidance due to interaction risk. Puppies under 12 weeks and pregnant or nursing dogs should only receive medications under direct veterinary supervision.
Call your vet or go to an emergency animal hospital immediately if your dog shows: difficulty breathing, extreme facial or throat swelling, vomiting or diarrhea after the dose, pale or white gums, collapse or weakness, or no improvement in severe symptoms within 30 minutes. Anaphylaxis in dogs is a medical emergency — antihistamines alone cannot treat it.