Most dogs take diphenhydramine at 1 mg per lb (2–4 mg/kg) every 8–12 hours, with a plain “diphenhydramine only” product and a veterinarian’s direction.

Most vets dose diphenhydramine at 2–4 mg/kg per dose each 8–12 hours, using plain diphenhydramine only.

Most vets use 2–4 mg/kg every 8–12 hours, but puppies should get a veterinarian’s OK and a low-end, weight-based dose.

A common starting dose is diphenhydramine 1 mg per pound per dose, given every 8–12 hours, once your vet says it fits your dog.

A typical diphenhydramine dose for many dogs is 1 mg per pound per dose, given every 8–12 hours when a vet says it fits.

A 30-lb dog commonly lands around 25–50 mg of plain diphenhydramine per dose, spaced 8–12 hours apart, with a veterinarian’s go-ahead.

A typical 40-lb dog dose is 40 mg of plain diphenhydramine per dose, given every 8–12 hours, unless your veterinarian has set a different plan.

A common starting dose for a 25-lb dog is 25 mg per dose, given every 8–12 hours, using diphenhydramine as the only active ingredient.

A 40-lb dog is commonly dosed at 40 mg of diphenhydramine per dose, but the right amount depends on your dog and the product.

For a 30-lb dog, vets often use 1 mg per lb per dose, yet health issues and mixed-ingredient products can change what’s safe.