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Cephalexin Side Effects in Dogs

Oh no! Your veterinarian has diagnosed your dog with an infection! They sent you home with a bottle of weird, sulfur-smelling capsules called Cephalexin. Should you give the pills to your dog? What are the Cephalexin side effects in dogs you should watch for?

In this post, we will cover everything you need to know about cephalexin, and how to give it to your dog to minimize any bad side effects.

The good news is that most dogs tolerate this medication with no problems! Chances are, your dog will come through this without having any nasty side effects.

Cephalexin Side Effects in Dogs

Cephalexin is a broad spectrum antibiotic. It is in the same family as the antibiotic penicillin.

A broad spectrum antibiotic is one that can kill a lot of different kinds of bacteria. Cephalexin is a very commonly used antibiotic in veterinary medicine, because it kills many of the bugs that cause infections in dogs.

Most dogs can take cephalexin without having any side effects,  but some dogs are more sensitive, and some can even be allergic! If your dog has ever had a reaction to penicillin, be sure to talk with your veterinarian about whether Cephalexin is a good option for them.

Always follow the instructions and make sure your dog completes the entire course of antibiotics. Antibiotic resistance is a real danger, evidenced by the video below:

The Antibiotic Apocalypse (antibiotic resistance in pets)
Watch this video on YouTube.

Also, there is new research out in humans that indicates that taking probiotics after using antibiotics may actually prevent the intestinal bacteria from returning to normal.

If you want to use a probiotic while giving your dog Cephalexin, then be sure to give the probiotic a few hours after the antibiotic. If you give them together, the antibiotic may just wipe out the probiotic in the stomach as they are digested together.

Cephalexin Smells Weird

Just a warning- Cephalexin has a strange odor. It is described as a sulfur-like smell by some. I always thought it smelled like a wet dog myself. Every time I opened a bottle and counted out a prescription, the wet dog analogy would strike me.

So if you open your prescription and smell something funky, don’t worry! This is normal; there is nothing wrong with the medication.

Why Use Cephalexin?

Cephalexin is a great option for a host of different kinds of infections. Since it is broad spectrum, veterinarians don’t have to know for sure exactly what kind of bacteria they are treating (saving you money).

Skin infections, urinary tract infections and respiratory infections are all often treated using Cephalexin. If the infection doesn’t respond in a week or 10 days, your veterinarian may switch to a different antibiotic.

They may also extend the course of treatment if the antibiotic is working, but the infection is still around. That’s why vets like to do follow-up rechecks when a dog is taking antibiotics.

Alternatives to Cephalexin

Sometimes, a dog doesn’t respond well to a medication. I have one dog who is very sensitive to another antibiotic. No matter what we do, she vomits within 30 minutes of getting it every single time. So that antibiotic isn’t a good option for her, and we have to use another when she is sick.

If you are having problems with cephalexin side effects in dogs, then talk to your vet. There may be other options for you to try.

Other Antibiotics

Cefpodoxime is the name of another antibiotic that is used for many of the same infections as Cephalexin. It comes in tablets, and the dose for it is usually much lower than the Cephalexin. It is also only given once a day, rather than every 12 hours. This dosing schedule might work better for your family.

Cefpodoxime is a lot more expensive, though. One reason that Cephalexin is so commonly prescribed is that is is one of the least expensive antibiotics.


Cephalexin is a common antibiotic used in dogs. The side effects are often mild, and are usually just signs of an upset stomach. You can prevent this by giving the medication with a meal. If you run into any problems with giving cephalexin to your dog, contact your vet.

Good luck! I hope your dog is back to full health soon!

I want to thank you for taking the time to read this post. Please feel free to email me or comment by using the form below. You can find me at: [email protected]


Jen Clifford has a B.A. in Biology from Reed College. She was a field biologist for several years and then spent 10 years working in veterinary medicine as a receptionist and technician.  Jen is currently a freelance writer living in the Pacific Northwest with her tribe of pets. She is a passionate animal lover who is dedicated to helping people find solutions to their pet-related challenges. You can find more of her work on her website

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