If you suspect your dog has ingested too much Benadryl, immediate action is crucial. Here are the steps to take: Contact Your Veterinarian Immediately: The first and most important step is to contact your veterinarian or a local emergency animal clinic.
Detailed Benadryl dosage information. What happens if I miss a dose? Since Benadryl is used when needed, you may not be on a dosing schedule. If you are on a schedule, use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose.
What are the long-term effects of giving my dog too much Benadryl?How long does Benadryl stay in a dogs system?What happens if a dog gets too much Benadryl and has a seizure?

Yes, giving a dog too much Benadryl can definitely be harmful. Benadryl (diphenhydramine) is an over-the-counter antihistamine that is commonly used to treat allergies in both humans and dogs.
Can Too Much Benadryl Kill A Dog? It depends on the individual dog and the dosage of benadryl they are taking. Some dogs may be able to tolerate a higher dosage of benadryl while others may not.

How much benadryl do I give a dog for car sickness?
What Happens If My Dog Has Too Much Benadryl? No matter how safe Benadryl is, if its given in too high of a dose, your dog will suffer from it. An overdose can be mild or it can be severe; it all depends on how much youve given and your dogs current health.
How much Benadryl is fatal for a dog? The lethal dose (LD50) for diphenhydramine in dogs ranges between 24 to 30 mg/kg BW by IV administration, and death has been attributed to neuromotor excitement and convulsions, followed by respiratory failure and myocardial depression (16).