How Much Benadryl Can I Give My Dog [Dosage Calculator]

This content was reviewed and fact-checked by veterinarian Dr. Aukse Caraite, DVM.

Whether your dog is suffering from allergies, an insect bite, or a stressful situation like travel or fireworks, Benadryl (diphenhydramine) is one of the most commonly recommended over-the-counter medications for quick relief. But while it’s safe for most dogs when dosed correctly, giving the wrong amount can be dangerous. That’s why we created this Benadryl dosage calculator for dogs—to help you quickly and safely determine how much Benadryl to give based on your dog’s weight. In this guide, you’ll also find dosage charts, safety tips, and answers to frequently asked questions to ensure you’re treating your pup effectively and responsibly.

How Much Benadryl Can I Give My Dog?

The standard Benadryl dosage for dogs is 1 mg of Benadryl per pound of body weight, given 2 to 3 times daily (every 8–12 hours). Most veterinarians follow this guideline when recommending over-the-counter dog antihistamines like Benadryl for pets experiencing allergies, itching, insect bites, or mild reactions. Children's Liquid Benadryl formulation is often recommended for dogs under 10 pounds, as it allows for more precise dosing than splitting standard adult Benadryl tablets. However, if your dog dislikes taking pills or you find it difficult to cut tablets, Children's Liquid Benadryl is safe for dogs of all sizes.

Benadryl product recommendations based on their type and strength:

Product Type	Common Strengths	Best For
Adult Benadryl tablets	25 mg, 50 mg	Medium to large dogs (25+ lbs)
Children’s liquid Benadryl	12.5 mg per 5 mL (1 tsp)	Small dogs under 10 lbs
Smaller-dose tablets	15 mg	Small to medium dogs (10–15 lbs)

Benadryl Table Dosage Chart for Dogs (By Weight)

Benadryl Liquid Dosage Chart for Dogs

Dosing chart for dogs taking liquid Benadryl.

Types of Benadryl to Avoid Giving Your Dog  

⚠️ While diphenhydramine hydrochloride is the active ingredient in most U.S. Benadryl products (commonly referred to as "American Benadryl"), not all Benadryl products are safe for dogs. In countries like the U.K. and Denmark, Benadryl may contain acrivastine or cetirizine, which are ingredients not well-studied in dogs.

🛑 If you're in Europe, always check that the product contains diphenhydramine—it’s the only active ingredient in Benadryl that’s considered safe for dogs when dosed properly.

Benadryl Forms to Avoid

When using American Benadryl (diphenhydramine), avoid the following formulations:

• Liqui-gels or gel capsules: These soft capsules are difficult to cut or dose precisely. They also absorb differently in dogs compared to humans, potentially leading to inconsistent or incorrect dosing.
• Adult liquid Benadryl: This version typically contains alcohol, which is toxic to dogs even in small amounts. Always use alcohol-free children’s liquid Benadryl if you need a liquid form.
• Benadryl Allergy Plus Congestion: Contains phenylephrine HCl, a nasal decongestant that is dangerous for dogs and can cause elevated blood pressure, vomiting, and severe health issues.
• Extra strength Benadryl: Often available in 50 mg tablets, which may be safe for large dogs under veterinary guidance, but can easily lead to overdose if not dosed accurately. Most vet-approved dosing is based on 25 mg tablets, making standard strength the safer option.
• Time-release or extended-release (ER/XR) tablets: Dogs digest medication differently than humans, and time-release coatings can result in delayed or uneven absorption, leading to accidental overdose or reduced effectiveness.

Safety Dosage Guidelines

Make sure you adhere to these safety tips before giving Benadryl to your dog.

1. Use only plain Benadryl with only diphenhydramine as the active ingredient.

• Avoid products with added ingredients like:
  • Acetaminophen (can be toxic to dogs)
  • Pseudoephedrine or other decongestants (dangerous and potentially fatal)
  • Alcohol or xylitol in liquid formulas (both are toxic to dogs)

2. Follow the proper dosage: Measure accurately, especially with liquid formulations. Start with a lower dose for small or sensitive breeds.

3. Avoid if your dog has:

• Urinary retention or prostate issues
• Heart disease
• Glaucoma
• High blood pressure
• Seizure disorders
• Hyperthyroidism

4. Check with your veterinarian first if:

• Your dog is under 12 weeks old
• Your dog is pregnant or nursing
• Your dog takes other prescription medications

5. Watch for side effects: These include drowsiness, dry mouth, urinary retention, and mild digestive upset. Rare but serious side effects include Hyperactivity or agitation, rapid breathing or heart rate, vomiting or diarrhea, or seizures

What to Do If A Dog Reacts Badly to Benadryl

Dogs showing worsening symptoms, such as blood in their vomit or stool, difficulty breathing, weakness, or collapse, should be taken to the veterinarian immediately.

1. Contact a veterinarian immediately: Even if your dog seems fine, contact your veterinarian or an emergency pet poison hotline right away. This includes services like the ASPCA Animal Poison Control Center or Pet Poison Helpline at 1-855-764-7661. If you can't reach your vet, you can chat live with a registered online veterinary professional via our online vet chat or video chat support (24 hours a day, 7 days a week). You can also schedule an at-home veterinary appointment with The Vets, a mobile veterinary service that provides at-home vet care nationwide for just about everything.

2. Gather important information: When speaking to a vet, provide the quantity consumed (estimate if unsure), the time of ingestion, and the dog’s weight and breed (to assess potential risk).

3. Follow veterinary instructions: The vet may suggest monitoring at home or emergency treatment at the clinic.

• Keep your dog calm and prevent them from eating anything else.
• Be prepared to transport your dog to the vet quickly if advised.
• Bring any remaining Benadryl or packaging to help the vet assess the situation.

🧬 MDR1 Sensitivity and Benadryl

Some dogs carry a genetic mutation in the MDR1 (Multi-Drug Resistance 1) gene, which affects how their body processes certain medications. This mutation is prevalent in herding breeds like Collies, Australian Shepherds, and Shelties.

While Benadryl (diphenhydramine) is generally considered safe for most dogs, those with the MDR1 mutation may be more sensitive to its effects or to other medications that might be used alongside it—such as sedatives, anti-nausea drugs, or decontamination treatments in emergency scenarios. Knowing your dog’s MDR1 status is crucial if:

• You ever need to use Benadryl alongside other medications.
• Your dog is receiving long-term allergy management.
• You want to avoid adverse drug reactions during emergency treatment.

The EasyDNA MDR1 test is a reliable way to determine if your dog has this mutation. It allows your vet to tailor medication choices safely, including when Benadryl is considered.

Pro tip: If your dog is a herding breed or mixed with one, consider testing before using any medications, even over-the-counter ones like Benadryl.

Calculate Benadryl Dosage For Dogs Manually

Use these formulas to manually calculate your dog's Benadryl dosage.

Tablet

Use this method if you're using standard Benadryl tablets (typically 25 mg per tablet):

1. Standard dose: 1 mg per 1 lb of body weight
2. Tablet strength: Most adult Benadryl tablets contain 25 mg of diphenhydramine
3. Formula: Dog’s weight in pounds ÷ 25 = number of tablets to give

Example: 50 lb dog → 50 ÷ 25 = 2 tablets

Liquid

Use this method if you're using liquid Benadryl (12.5 mg per 5 mL):

1. Standard dose: 1 mg per 1 lb of body weight
2. Liquid concentration: 12.5 mg per 5 mL = 2.5 mg per 1 mL
3. Formula: Dog’s weight in pounds ÷ 2.5 = mL to give

🧪 Example: 25 lb dog → 25 ÷ 2.5 = 10 mL

Frequently Asked Questions

The Bottom Line & Alternatives

Benadryl can be a safe and effective over-the-counter remedy for dogs suffering from allergies, insect bites, mild anxiety, or travel sickness—but only when dosed correctly. Whether you’re using tablets or liquid, knowing your dog’s weight and the exact dosage is key to avoiding complications and ensuring fast relief. Always use plain diphenhydramine without added ingredients like decongestants, acetaminophen, or alcohol. Stick to the standard guideline of 1 mg per pound of body weight, and consult your vet before giving Benadryl—especially if your dog has health conditions, is on other medications, or is under 12 weeks old.

If Benadryl isn’t providing enough relief or you’re looking for gentler, longer-term alternatives, you might want to explore CBD oil for dogs—which some pet owners use to naturally manage both allergies and anxiety. You can also check out our guide to the best allergy medicine for dogs for prescription and non-prescription options beyond Benadryl. Concerned your dog’s symptoms may be caused by an underlying allergy? Getting a dog allergy test can help identify food or environmental triggers so you can treat the root cause—not just the symptoms. For dogs dealing with stress, travel anxiety, or loud noises like fireworks, Benadryl may not always be the ideal long-term solution. In that case, explore our calming strategies and products in how to calm dogs with anxiety.

With the charts, calculators, and tips in this guide, you now have everything you need to safely and confidently dose Benadryl—and understand when it might be time to try something more targeted.

Like It? Subscribe & Share!

* indicates required

First Name *

Email Address *

Dog Breed

Leave this field empty if you're human:

Sources

Canine Bible uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process and product review methodology to learn more about how we fact-check, test products, and keep our content accurate, reliable, and trustworthy.