When you go to your doctor for an annual exam, they frequently recommend drawing blood to check your cholesterol, thyroid, and glucose levels. They may order other tests as well based on your exam and history. Most often, your results will return as normal, indicating good health.
Veterinarians also recommend yearly blood work for pets for the same reasons. Even though your young dog or cat may seem completely healthy, we want to establish a baseline for liver, kidneys, glucose, etc., to monitor trends as pets age. It’s important to remember that cats and dogs age much more quickly than humans. That yearly exam is more like you seeing your doctor every five to seven years. A lot can change in that time.
So does it make sense to do yearly blood work on your pet, and what are veterinarians looking for? For our dog patients, a yearly heartworm and tick-borne disease test is very important. There are several brands of tests that can be used, but a common one is the 4Dx test, which stands for four diagnostic tests in one. With three drops of blood, it tests for antigens to heartworms and antibodies to three different bacteria spread by ticks: Lyme, Anaplasma, and Ehrlichia.
Positive results mean that your dog is infected with heartworms and/or has been exposed to a tick disease. Antibody tests don’t tell us if there is an active infection, only that your dog was exposed at some point. Often, your veterinarian will treat your dog the first time a tick disease test is positive, but that positive will remain for years. Having a dog test positive for a tick disease also tells us that flea and tick preventatives haven’t been used properly, long enough, or at all and that the dog’s humans may also have been exposed to tick diseases. If your dog tests positive for Lyme, getting a Lyme vaccine to help prevent infection in the future is very worthwhile.
Because cats are more resistant, but not immune, to tick diseases, their heartworm test doesn’t include tick disease testing. The Feline Triple tests for heartworms, feline leukemia (FeLV), and feline AIDS (FIV). This test is most commonly done in young cats to make sure they didn’t pick up FeLV or FIV from their mother or if a cat comes in with a cough, which could be a sign of heartworms. Most veterinarians don’t recommend this test yearly but may recommend testing for FeLV and FIV on an adult cat or one that spends time outside.
Besides testing for specific diseases, routine blood work also gives veterinarians a lot of information about internal organs. The tests are pretty much the same as your physician would run and tell similar things. A complete blood count (CBC) gives us information about red and white blood cells and the platelets circulating in the bloodstream. Too few red blood cells indicate anemia, which could indicate chronic inflammation or disease, bone marrow problems, or kidney issues. Too many white blood cells indicate infection somewhere or leukemia. Too few platelets indicate a clotting problem, and a high number of platelets means inflammation somewhere in the body. Parasites of the red blood cells, such as Babesia, can sometimes be seen. A CBC is very important before surgical or dental procedures. If your pet doesn’t have enough platelets to help blood clot, we don’t want to cut them.
The broad term chemistries—mainly enzymes, electrolytes, proteins, and hormones—essentially encompasses all the tests of the internal organs. For young animals, we generally check glucose, liver enzymes (ALT, ALP), kidney values (BUN, creatinine, SDMA), proteins (albumin, globulin), and electrolytes (sodium, potassium, chloride). These numbers tell us if the pet is potentially heading toward diabetes, if the liver and kidneys are working normally, if there’s any protein being lost in the intestines or kidneys, and if their adrenal glands are properly regulating their electrolytes.
Once an animal is older (generally at least nine years of age), we add on additional testing, such as cholesterol and thyroid hormone levels. While pets don’t live long enough to develop hardening of the arteries, increasing cholesterol levels point to an underactive thyroid gland. Older cats can develop an overactive thyroid gland, but this rarely occurs before age nine. Dogs can become hypothyroid, causing weight gain and a poor haircoat, at any time, though more commonly as they age.
Urine is something else we frequently test, particularly in older animals. The concentration of the urine gives us a look at how the kidneys are functioning and is more sensitive than the blood kidney values. We can also pick up urinary tract infections, bladder cancer, crystal or bladder stone formation, diabetes, and the occasional bladder parasite with a urine sample. The first morning urine sample is often the most helpful (unless your veterinarian suspects a bladder infection, then a sterile sample collected at the vet’s clinic is better), so we love it if you can collect a fresh sample before your appointment.
Poop is another bodily output that should be checked yearly. Many heartworm preventatives also protect against some common intestinal worms, but not all. If your veterinarian sends off fecal samples to a lab, they’re looking both for parasites and worm eggs in the stool sample as well as antigens to adult worms, such as roundworms, hookworms, whipworms, and tapeworms. Cats are not immune to intestinal worms even if they are kept inside all the time. Roundworm eggs can be found in potting soil or insects.
It’s in the best interest of your pet to have blood work done every year. Sometimes, anxiety and temperament mean we can’t get blood easily; these are the pets that should get pre-visit antianxiety medication first. Your veterinarian can monitor trends to catch kidney disease very early, changing thyroid values, and have a baseline to compare to in case your pet gets sick. If you have questions about your veterinarian’s recommendations, be sure to ask.