Sometimes even the most attentive owners mistakenly dismiss signs of serious illness. Here are three you shouldn’t ignore:

1. Listlessness

If your normally active cat or dog would suddenly rather sleep than play, don’t excuse this behavior as mere exhaustion. It’s actually the first, subtle sign your pet can give that something is very wrong. Rush your kitty or pup to a vet–his aloofness could mean he’s suffering from a potentially life-threatening illness, such as a urinary obstruction, kidney disease, pancreatitis, or cancer.

2. Vomiting and coughing

A cat will throw up a hairball now and then, but vomiting more than once a month could indicate kidney failure or inflammatory bowel disease. Coughing, meanwhile, is never normal. It’s often caused by asthma, which can lead to severe chronic lung disease or death without treatment. If your cat is diagnosed, an emergency inhaler and oral medication can help ease symptoms.

Dogs vomit occasionally (like if they eat too much grass), but rush your pup to the vet if she is vomiting a few times a day. There might be a foreign object stuck in her stomach or intestines. Dogs don’t get asthma, so coughing could signal bronchitis, pneumonia, a heart problem, or tracheal collapse (when weak cartilage in the airway hinders breathing). Treatments include anti-inflammatories and surgery.

3. Frequent urination attempts

if your male cat is squatting and straining, he might have a feline urethral obstruction (the tip of a cat’s urethra gets clogged by grit or mucous plugs). Having such an obstruction means your cat can’t urinate for days, resulting in severe pain, temporary kidney failure, and even death. If you own a male dog, similar symptoms can mean bladder stones or other obstructions. Your vet can remove the blockage or operate if needed.

Justine Lee, DVM, DACVECC, is a veterinary emergency critical-care specialist and the associate director of veterinary services at Pet Poison Helpline®. She is the author of the book It’s a Cat’s World…You Just Live in It. Copyright Prevention Magazine September 2009.