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For many dogs, diphenhydramine is dosed at 1 mg per pound (2–4 mg/kg) every 8–12 hours, after a vet says it fits your dog.

Most adults take 25–50 mg per dose every 4–6 hours, up to 300 mg in 24 hours, unless a clinician gives different directions.

Most vets start diphenhydramine at 1 mg per lb, but puppies need a vet’s OK, a plain product, and weight-based measuring.

Most dogs take diphenhydramine at 2–4 mg/kg per dose by mouth every 8–12 hours, with a veterinarian setting the safest target for your dog.

Most dogs get diphenhydramine at 1 mg per pound per dose, which equals 0.4 mL per pound when the liquid is 12.5 mg per 5 mL.

Most adults can take 25–50 mg every 4–6 hours, with a typical OTC daily cap of 300 mg, unless a clinician gives different directions.

For many toddlers, diphenhydramine is best skipped unless a child’s clinician has given a weight-based dose for a clear allergy reason.

Most Benadryl allergy tablets contain 25 mg of diphenhydramine HCl per pill, while some products use 50 mg or a liquid-measured strength.

A safe amount depends on your puppy’s exact weight, age, and the product label—so the right move is to confirm the dose with a vet first.

A 16-lb dog often gets 16 mg diphenhydramine per dose, every 8–12 hours, using a plain antihistamine only.