Your typically playful tabby would rather snooze than swat at her favorite feather teaser. Your Schnauzer has become a chowhound, gobbling his kibble and begging for more — yet he’s steadily losing weight. Are these signs your beloved cat or dog is simply more tired or hungry than usual? Or could your pet be sick?

Any unusual symptoms or changes in a pet’s behavior warrant a call or trip to the vet, says Sheldon L. Gerstenfeld, VMD, author of the “ASPCA Complete Guide to Dogs” and “The Cat Care Book.”

Since an animal can’t say if or where it hurts, the vet will rely first on what you can tell him to diagnose what’s wrong. So before you call, says Gerstenfeld, write down as much as you can about your pet’s symptoms and recent activities, including

  • when symptoms began
  • where your pet has been
  • if your dog or cat has been around other animals
  • if he or she has eaten anything unusual or potentially dangerous
  • if you’ve recently moved or brought a new baby or animal into the house
  • if you have new furniture or rugs (these are often treated with chemicals toxic to pets)

This information will help the vet decide if your pet needs tests. That lethargic kitty may truly just be tuckered out — or she could have cancer. The insatiable Schnauzer could have a thyroid problem or even diabetes. (The breed is prone to both.)

dog and cat going to the vet (Photo: Ermolaev Alexander/Shutterstock) 

Here are common dog and cat symptoms and what they can mean:

Eating more yet losing weight. In both dogs and cats, this odd combination of symptoms can signal diabetes. In cats, increased appetite coupled with weight loss is also a potential sign of hyperthyroidism.

Vomiting or diarrhea. Dogs in particular often have their noses to the ground— or in the garbage — so one episode of vomiting or diarrhea probably just means your pet ate something he shouldn’t have. However, vomiting or diarrhea accompanied by lethargy or lack of appetite could signal a serious gastrointestinal illness, parasitic infection or a blockage caused by swallowing rocks, sticks or kids’ toys. “We had one puppy with an entire arts and crafts center in its intestines,” says Gerstenfeld.

Call your vet immediately if you see blood — either bright red blood or digested blood, which resembles coffee grounds — in vomit or diarrhea. These can be signs of a gastric ulcer or a potentially fatal hemorrhagic condition. If your feline is an outdoor cat, consider the possibility that she might have swallowed rat poison.

Urinating more or less than usual. Diabetes symptoms in animals are similar to those in humans: increased thirst and urination. You may notice your kitty’s water bowl needs to be filled more often or your long-ago housebroken dog is peeing in the house. Other possible diagnoses: kidney disease or cystitis.

Like humans, animals are also more prone to dehydration and less-frequent urination when they age. But a cat who’s having trouble urinating is a medical emergency, says Gerstenfeld. That symptom often indicates a urinary tract problem or bladder stones; without intervention, toxins can quickly build up in the cat’s system. Animals with urinary tract problems or stones may have blood in their urine, though it may not be visible. A vet can detect it with a dipstick.

Breathing problems, chronic coughing or sneezing. These symptoms can be caused by a wide variety of ailments, making it especially important to provide your veterinarian with as much information as you can, says Gerstenfeld.

Some possibilities include a respiratory virus like kennel cough or pneumonia, irritation from the off-gassing of formaldehyde in new rugs or furniture, and blockage in a nostril caused by anything from a blade of grass to a tumor. Bring a pet with labored breathing to the vet immediately.

Related: Clean Carpet, Healthy Pets: How to Have Both 

Skin lumps and bumps. “Around 90 percent of masses in cats and 50 percent of masses in dogs are malignant,” says Gerstenfeld. Pet or massage your furball regularly. That way you’ll pick up on any unusual changes in his or her body. Typically, a growth you can put your fingers all the way around will be benign, such as a lipoma (fatty tumor). The only way to be sure is to have your vet aspirate or biopsy the lump, so have it checked out as soon as you notice it. 

Denise Foley is a veteran health writer and a former contributing executive editor at Prevention magazine.