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If your usually happy pup suddenly isn’t acting like themself, you’re not alone in wondering how to tell if your dog is sick. Dogs are experts at masking discomfort, which means even small changes can be meaningful. At 10 West Bird & Animal Hospital in San Antonio, TX, we help pet owners sort through the confusing mix of dog illness symptoms so they know what’s normal and what’s worth a closer look.

Below are some of the most common signs your dog is sick, along with guidance on when to take your dog to the vet.

1. Changes in Appetite

A sudden drop in appetite, or a sudden increase, can be one of the earliest symptoms your dog is sick. Skipping meals occasionally may be no big deal, but consistent changes often signal underlying digestive issues, dental pain, or metabolic conditions.

2. Vomiting or Diarrhea

Not every upset stomach is an emergency, but repeated vomiting or diarrhea isn’t something to wait out. Frequent GI issues can indicate infections, dietary indiscretion, toxins, pancreatitis, or other conditions that need prompt attention.

3. Low Energy or Lethargy

If your energetic sidekick seems to lose their spark overnight, take note. Lethargy is one of the most common sick dog symptoms and often pairs with other problems such as fever, pain, or infection.

4. Breathing Changes

Any noticeable shift in the way your dog breathes deserves attention. This includes:

• Rapid breathing
• Labored breathing
• Persistent coughing
• Wheezing

A calm respiratory pattern is normal. Anything else is a sign to call your veterinarian so your dog’s heart and lungs can be checked.

5. Excessive Thirst or Frequent Urination

If you’re filling the water bowl more often than usual or making extra trips outside, your dog may be dealing with a hormonal condition, kidney concerns, or diabetes. These dog illness symptoms tend to progress gradually, making early detection especially important.

6. Sudden Weight Loss or Weight Gain

Unexplained weight changes aren’t just cosmetic. They can be associated with thyroid disease, digestive disorders, chronic illnesses, or medication reactions. Even if your dog seems otherwise fine, unexpected weight shifts are a reason to schedule a wellness exam.

7. Behavioral Changes

Behavior is one of the clearest windows into how a dog feels. You may notice:

• Irritability
• Avoiding family members
• Increased clinginess
• Restlessness
• Uncharacteristic aggression

These changes often reflect pain or discomfort, even when no physical clues are obvious. Paying attention to emotional cues is a key part of understanding how to tell if your dog is sick.

8. Limping or Mobility Issues

A limp doesn’t always mean a sprain. Older dogs may be battling arthritis, while younger dogs might have soft-tissue injuries or joint problems. If your dog hesitates to jump, climb stairs, or rise from rest, it’s time to evaluate whether pain is involved.

9. Skin, Coat, or Ear Problems

The outside often reveals what’s happening inside. Signs to watch for include:

• Constant scratching
• Hair loss
• Red or flaky skin
• Ear odor
• Ear discharge

These symptoms may point to allergies, infections, parasites, or hormonal imbalances.

10. Bad Breath

We all expect a little “dog breath,” but truly foul odors usually indicate dental disease. Left untreated, oral infections can spread and cause broader health issues, making regular dental checkups especially important.

Worried Your Dog Might Be Sick?

Catching sick dog symptoms early can make a big difference in treatment and comfort. If you’ve noticed any of these signs your dog is sick, trust your instincts. Subtle changes matter. 

Our doctors and staff provide comprehensive care, including advanced diagnostics, dental care, laser therapy, and other services. To schedule an appointment or discuss your concerns, call (210) 696-1700. We’re here to support your pet’s health every step of the way.