Cephalexin Side Effects in Dogs – What to Watch Out For

Today, I’d like to talk about Cephalexin, a common antibiotic prescribed for dogs. While it’s an effective weapon against bacterial infections, like all medications, it comes with its own set of side effects.

As a dog owner myself, I know how worrying it can be when our furry friends aren’t feeling well, and as a vet, I know how important the right treatment is, which is why I want to help you with this topic.

Key Takeaways

  1. Cephalexin is an antibiotic used to treat specific bacterial infections in dogs, such as skin, urinary tract, and respiratory infections.
  2. The dosage is typically based on the dog’s weight, with a common range of 10 to 15 mg per pound, administered every 8 to 12 hours.
  3. Common side effects include gastrointestinal issues, allergic reactions, and, in rare cases, effects on kidney and liver function or neurological symptoms.
  4. If Cephalexin is not suitable for a dog, alternatives like Amoxicillin or Clavamox may be considered, subject to a vet’s advice.

What is Cephalexin?

This medication is an antibiotic that belongs to the cephalosporin family. It’s primarily used to treat bacterial infections in dogs, including skin infections, urinary tract infections, and respiratory infections. By inhibiting the growth of bacteria, it helps in quick recovery.

It’s important to note that it’s not effective against viral infections. Cephalexin works by disrupting the bacteria’s cell wall formation, leading to the death of the bacteria. It is often chosen for its effectiveness and minimal side effects compared to other antibiotics.

Common Side Effects in Dogs

Like any medication, Cephalexin can cause side effects. While most are mild, some can be severe. Here’s what you need to know:

1. Gastrointestinal Issues

Many dogs experience gastrointestinal disturbances like vomiting, diarrhea, and loss of appetite. These symptoms are usually mild and resolve with time. In some cases, these symptoms may be alleviated by administering the medication with food.

However, persistent or severe gastrointestinal symptoms should be reported to a veterinarian, as they may indicate a more serious condition or an adverse reaction to the medication.

2. Allergic Reactions

Some dogs may exhibit allergic reactions to Cephalexin. Symptoms include hives, swelling, difficulty breathing, or a sudden onset of diarrhea or vomiting. Immediate veterinary attention is crucial in these cases. Allergic reactions can escalate quickly and may become life-threatening, necessitating emergency treatment.

Owners should be vigilant and inform the vet of any known allergies before starting the treatment.

3. Effects on Kidney and Liver Function

In rare cases, Cephalexin can affect kidney and liver function. Monitoring these organs is essential, especially in dogs with pre-existing conditions. Regular blood tests may be required to ensure the medication is not causing harm to these organs.

If there are signs of organ dysfunction, alternative treatments should be considered.

4. Neurological Symptoms

Though rare, some dogs may show signs of:

  • agitation,
  • confusion,
  • or seizures.

If these occur, contact your veterinarian immediately. These symptoms are more likely in dogs with a history of neurological disorders. It is also crucial to differentiate these symptoms from those of the underlying infection, as they can sometimes appear similar.

When to Use It?

Cephalexin is specifically prescribed for bacterial infections such as skin infections, bone infections, wound infections, or respiratory tract infections in dogs. It’s vital to understand that this medication is not effective against viral or parasitic infections, underscoring the importance of accurate diagnosis by a veterinarian.

When used without proper veterinary guidance, Cephalexin can be misapplied for conditions it doesn’t treat, leading not only to ineffective treatment but also to potential harm to your pet. Overuse of any antibiotic, including Cephalexin, can contribute to the development of resistant strains of bacteria.

This makes future infections more challenging to treat, not only in your pet but in the canine population at large. It’s crucial to follow your vet’s advice and not use it as a catch-all antibiotic.

Dosage and Administration

Give Your Dog a Pill

The dosage of Cephalexin is typically calculated based on the dog’s weight, with the usual range being 10 to 15 mg per pound of body weight, administered every 8 to 12 hours.  Your vet might adjust this dosage based on the severity of the infection and the overall health of your dog.

It’s important to administer the medication at evenly spaced intervals to maintain a consistent level of the drug in the dog’s system.  Cephalexin is available in tablet or liquid form, and while some dogs may take it easily with food, others may require a pill pocket or other method to ensure ingestion.

It’s essential to complete the entire course of the medication, even if your dog seems to improve before the medication is finished, to ensure that the infection is fully resolved and prevent recurrence.

Alternatives to Cephalexin

Clavamox Dogs

If your dog shows signs of an allergic reaction to Cephalexin or if it’s not effective in treating the infection, there are several alternatives. Other antibiotics like Amoxicillin or Clavamox may be suitable. These alternatives work differently and may be more suitable for dogs with specific sensitivities or infections resistant to Cephalexin.

Amoxicillin, for instance, is often used for similar infections and is sometimes preferred for its gentler impact on the digestive system. Clavamox, a combination of amoxicillin and clavulanic acid, is effective against a broader range of bacteria.

Always discuss these options with your vet to find the most appropriate and safe alternative for your pet.

How to Prevent Side Effects?

Dogs Eating Habits

To minimize side effects, it’s also advisable to monitor your dog’s eating habits and stool consistency, as changes can be early indicators of side effects. Keeping your dog well-hydrated is crucial, especially if they experience gastrointestinal side effects like vomiting or diarrhea.

Along with hydration, providing a balanced diet can help maintain your dog’s overall health and resilience while on medication. Regular check-ups with your vet are vital not only to monitor your dog’s response to the medication but also to adjust the treatment plan if necessary.

If side effects become severe or persistent, your vet may decide to alter the dosage or switch to a different antibiotic. It’s also important to inform your vet of any other medications or supplements your dog is taking, as these can interact with Cephalexin.

“Dogs have a unique ability to metabolize certain antibiotics, including Cephalexin, differently than humans. This is partly due to their faster digestion rate and the specific way their liver enzymes work. It’s fascinating how veterinary medicine tailors treatments like antibiotic courses to suit these unique aspects of canine biology, ensuring effective and safe treatment for our four-legged friends.”


Can Cephalexin be used to treat ear infections in dogs?

Yes, this medication can be prescribed for ear infections in dogs, especially if they are caused by bacteria. However, it’s important to have a vet diagnose the specific type of infection, as some ear infections may be caused by fungi or mites, against which Cephalexin is ineffective.

How long does it usually take for Cephalexin to start working in dogs?

The medication typically begins to work within one to two days after starting the medication. It might take longer to see visible improvements in your dog’s symptoms. It’s crucial to continue the medication for the full prescribed duration.

Is Cephalexin safe for pregnant or nursing dogs?

The safety of Cephalexin in pregnant or nursing dogs isn’t fully established. If your dog is pregnant or nursing, it’s essential to consult your veterinarian for the safest treatment options.

Can Cephalexin interact with other medications my dog is taking?

Yes, it can interact with other medications, which may lead to increased side effects or reduced effectiveness. Always inform your vet about any other medications, supplements, or herbal treatments your dog is receiving.

What should I do if I miss a dose of Cephalexin for my dog?

If you miss a dose, give it as soon as you remember. If it’s almost time for the next dose, skip the missed dose and continue with the regular schedule. Do not double the dose to catch up.

Are there any specific storage instructions for Cephalexin?

The medication should be stored at room temperature, away from light and moisture. The liquid form of the medication should be shaken well before use and typically has a shorter shelf life. Always check the expiration date and storage instructions on the label.


While Cephalexin is a valuable tool in treating bacterial infections in dogs, being aware of its potential side effects is crucial for every responsible dog owner. Observe your dog’s reaction to the medication and maintain open communication with your veterinarian to ensure the health and well-being of your furry friend.