How Much Benadryl Can I Give My Cat?

We recently drove from Massachusets to Missouri for a full military move. So, with 4 cats, I seriously contemplated whether it would be a good idea to sedate my cats using Benedryl. I didn’t use it for that but I did for my cat who had an allergy and was losing her hair. I asked my vet about this and did some research to find the general amounts for cats, what types are there and if it’s safe.

Well, how much Benadryl can I give my cat? My vet office doses Benadryl at about 1 milligram per pound for cats. To start you could go with .5 milligrams per pound of body weight. If you wanted to use liquid Benadryl, you’ll most likely need about five or six milliliters of liquid (available at a concentration of 12.5mg/5ml) for a 15-pound cat to get a more precise dose.

First off, talk to your vet before giving your cat Benadryl and if it’s ok.

Especially if they’re scratching excessively, your vet can detect any other issues other than allergies too with that visit.

Tanta allergy hair loss on lower back with scabs

Cortisone treatments might be prescribed if it’s really extreme.

And get this, not only is using Benadryl relatively safe for cats but it’s helpful to calm them for longer trips and can relieve them from basic allergy symptoms.

With cats, those allergies inflame the skin (the itches) and with us humans it attacks our sinuses.

You can Get Basic Benadryl from Walmart.

Now let’s dig a bit deeper into how this works so you can make a better decision to use this with your cat.

Giving Your Cat Benadryl: Taking A Closer Look

The first thing to do is make sure the active ingredient is diphenhydramine

This is an antihistamine which tames symptoms of allergies

This means that it deals specifically with histamines inside the body. 

These are what your immune system makes to get rid of things in your body that bug you.

Get this:

When you get allergy symptoms from pollen, pet dander, or dust like:

  • Redness of the skin
  • Swelling
  • Sneezing
  • Inflammation
  • Itchy eyes
  • A runny nose

That’s the histamines attacking it and trying to get it out of your body.

Like a bouncer at a club.

That’s where the anti-histamines come in to help relieve those allergy symptoms.  

Taking Benadryl blocks them from doing so, preventing symptoms.

Note:  If you’re treating your cat using Benedryl and they have an allergic reaction or your cat gets worse or doesn’t get better, go see a Veterinarian immediately.

If there’s no improvement you could also discuss with your vet other antihistamines that work better than Benadryl.

Allergic reactions of cats taking Benedryl could be:

  • swelling of the face
  • difficulty breathing
  • Collapse

Please take your cat to an emergency veterinary facility for immediate medical care for a potentially fatal allergic reaction.


Precautions And Guidelines Before Giving Your Cat Benadryl

Like I mentioned above, only use plain Benadryl (diphenhydramine) as the active ingredient.

Always stay away from those types that also contain other medications and ingredients for other symptoms because they contain other active ingredients.

Like if you have a cold, or congestion which uses acetaminophen or pseudoephedrine (which can be found in some non-drowsy formulas)… this can be lethal to cats.

[Read more here.]

Benadryl comes in two types:

  • 12.5 and 25 milligrams (mg) tablets or capsules.
  • 12.5 mg per 5 milliliters (mL) liquid suspension. (depending on what the bottle says)

Normally tablets aren’t used since the dose is so small.

Plus it’s easier for a more exact amount (dose) using the liquid Benadryl.

Giving pills to cats is just bananas but I give some ideas below.

  1. For a 5 lb cat:  give 2 ml of liquid
  2. For a 10 lb cat:  give 1/2 of a 25 mg tablet
  3. For a 25 lb cat:  give 1 (25 mg tablet)

My vet recommends giving the dose once every 12 hours for 2 weeks to determine the effectiveness.

Precautions For Giving Benadryl To Your Cat:

I mentioned before about being absolutely sure that the Benadryl has only one active ingredient in regular strength:


Please always consult with your vet to make sure this will be ok.

Especially if your cat is taking other meds for other issues… like tranquilizers. (do not give Benadryl to your cat if they are on tranquilizers.)

This is the list of drugs which Benadryl can react with:

  • Amitraz
  • Selegiline
  • Epinephrine
  • Depressants of the Central Nervous System
  • Furazolidone
  • Warfarin sodium
  • Heparin calcium or sodium

Please don’t give your cat this thinking it will eliminate or mask a symptom their having.

Make sure you know what the underlying issue is.

Be cautious when giving to cats with:

  • heart problems
  • bladder disorders
  • Hyperthyroidism
  • high blood pressure
  • pregnant cats

Always ask your vet.

Liquid Benedryl For Cats Dosage Chart

The max dose for cats liquid version is 1 mg per 1 lb of body weight. (I would go .5 mg to start)

The max dose for cat pill version is .5 mg per 1 lb of body weight. (So, 16 lb cat x .5 = 8. That’s a quarter of a 25mg Benadryl tab.)

The dose for cats is typically 2-4 mg for the average sized cat and this can be given every 8-12 hours.

For example:

a 2 mg dose for a cat = 0.8 mL

a 3 mg dose for a cat = 1.2 mL

a 4 mg dose for a cat = 1.6 mL –

Go get yourself a 1 mL – 3 mL syringe depending on what you need for your cat.

You can find oral syringes at most stores or get them online.

Using these will help with the accuracy of the dose.

For comparison, one tablespoon contains 30 mL!

For my 17 lb. cat, my vet said 1 ml or a 1/4 tsp. Of Benadryl – 2 times a day.

Dosage is a very touchy subject, I’ve just listed here many ways to administer this. Always ask your vet.

How To Give Your Cat Benadryl

Every cat is different.

Their tastes and how they like to eat are all different.  

Like I said before, giving cats any type of medication is bananas.

Note: They may foam at the mouth, scream a little and run around to get away from you.

Prepare a kit with a variety of ways to help alleviate the stress for your cat after giving meds.

And a towel, for the mess.

Below is a great video by Cats And Pats:


You could try these various ways to give your cat Benadryl listed below:

Compounding of medication for cats

This simply means mixing your drug with others to meet the needs of your cat.

If you’re not able to give your cat the pill or liquid med at home, your vet might have the drug compounded into a flavored liquid that your cat will take.

Food Grade Diatomaceous Earth – make sure it’s food grade.

You can give your cats food grade diatomaceous earth for their symptoms as well. This is mainly used for flea prevention but you could also add it to your cat’s diet.

[Visit here to see how to give this to your cat]

It can help clear up the underlying allergy problem and your cats overall health.

What Are The Side Effects Of Benedryl For Cats?

There are side effects for everything, right?!

Well, the same way we get and suffer from them you cat will too.  

Don’t panic too much because it means the meds are taking effect to fight those allergies.

Side effects of Benadryl for cats:

  • Hyperexcitability in cats
  • Sedation
  • Tired
  • Sleepy
  • Dizzy
  • Coordination off
  • Constipation
  • Dry mouth
  • Dry nose
  • Dry throat
  • Hard time urinating
  • Upset stomach
  • Blurred vision
  • Tremors
  • Loss of appetite
  • Nausea

Always try your best not to overdose.

In case of an overdose your cat can have these symptoms:

  • Breathing difficulties
  • Seizures
  • Coma
  • Death


Benadryl is semi-effective in eliminating the symptoms of allergies in cats.  It’s definitely not as strong for them as is for us humans.  

They’ll likely be too drowsy to scratch or lick.

It should work about one hour after you give it to them.

In some cases…

A week or two can go by before its effects are noticed.

Causes Of Cat Allergies

In the last few months, I’ve been dealing with one of my cats who had a “ghost” allergy.

Meaning, I had no idea what was making her lose hair on her lower back by the tail.

I took her to the vet and he stated I could put her through a plethora of tests to try and pinpoint what was going on.

Which is why communication and making notes of how you care for your cat is so important.

Because I did this, we broke it down to the food I was feeding them.

It was a food allergy that was causing her hair loss and small scabby bumps.  It was either a flea allergy or food allergy. (miliary dermatitis)

I changed her food to fresh and it went away in a couple months!

Doing more research led to finding a few more ways that can cause allergies in your cat:

  • Biting Insects – Fleas (most common – dermatitis) They don’t have to bite your cat to cause itching, it’s their saliva that causes the allergy.
  • Airborne Allergens – Pollen, grass, and mold (feline atopic dermatitis)
  • Cutaneous Adverse Food Reactions – food allergies in cats
  • Medications – Vaccines

The bottom line is this…

It’s ok to give your cat Benadryl, it’s relatively safe.

Just make sure you ask your vet exactly what to, what to buy and ideas on how to give it to them.

It’s always best to give the liquid form, using a syringe (no needle) for a more exact dose.

Just know, Benadryl hasn’t been approved for veterinary use by FDA.

As a matter of fact, a majority of veterinarians suggest using Benadryl for cats suffering from allergy symptoms. (We all want happy cats!)

I’d love to know your thoughts on this or your experiences.

Leave me comments below! I read them all.

Related Questions:

Can cats take Benadryl for sneezing? It’s a good idea to see a vet if your cats are sneezing a lot. If your cat has mild seasonal allergies and is sneezing, Benadryl can help to stop it. But if your cat has a lung infection or any other respiratory disease, Benadryl will not relieve the sneezing.

Can I give a cat Benadryl for sleep? Benadryl has a sedative type effect for both cats and humans. If you need your cat to sleep or if you taking your cat on a plane, Benadryl is safe to take.

Can I give my cat children’s Benadryl? Giving your cat the children’s Benadryl with no dyes or flavor is ok, just make sure the dose is correct for the weight of your cat. This would be for the liquid form: 1 mg per 1 lb of body weight. Try an get a non-flavored version if possible, I don’t think cats would like that cherry flavor.

But if that’s all there is, get it.

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