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Health & Wellness

The basics of blood work for pets

What to know about why, and when, your vet will recommend running your dog or cat's blood work.

From time to time, your veterinarian might recommend running blood tests on your dog or cat, especially if your pet is older. It may seem strange to run blood work on an apparently healthy pet, but it’s good to get baseline numbers for our pets, and occasionally health issues are discovered through these routine tests.

“Running routine blood work is common practice for most veterinarians, especially if your pet is over 7 or 8 years of age,” Dr. Kelly Diehl, DVM, MS, Dipl. ACVIM (SAIM), a former vet and the senior scientific programs and communications adviser at Morris Animal Foundation, says. “Yearly blood work once a pet turns 7 years old can catch many diseases before they become bigger problems. And the earlier a disease is discovered, the better the long-term outcome for our pets will be.”

If your veterinarian recommends blood work, don’t fear. Blood draws don’t hurt your pets — there may just be a bit of discomfort when the needle is first inserted. 

Your vet will likely run a comprehensive panel, including a complete blood count (CBC), full chemistry and, if your pet is older, a thyroid level. This may sound like a lot, but these tests give your vet important information about your pet’s overall health.

What is a complete blood count?

“It’s important that pet parents educate themselves about the commonly measured items in a blood panel,” Dr. Diehl says. “If you’ve had any blood work yourself, you’ll probably recognize some of the components, but it’s important to remember that normal reference values for dogs, cats and people can vary a lot.”  

A CBC tells your veterinarian about your pet’s red blood cells, white blood cells and platelets levels. White blood cells fight infection, and an increase in the number of white blood cells in anyone can indicate mild or severe infections. Sometimes, overwhelming infections can deplete white cell lines, leading to a decrease in their numbers.

The body depends on red blood cells to carry blood to organs and muscles. Low numbers of red blood cells are called anemia, which can be life-threatening. When a pet is anemic, their tissues stand the chance of being deprived of oxygen. Red blood cell levels can also be too high, as is often the case in extreme dehydration

Then, there are platelets, which are necessary for blood clotting. When platelet levels are too low, your pet runs the risk of life-threatening clotting disorders.

“Your veterinarian will often check a chemistry panel for a procedure requiring general anesthesia, such as a teeth cleaning,” Dr. Diehl says. “Of course, additional blood work is often recommended if a pet is sick.”

RELATED: How much does a vet visit cost?

What is a blood chemistry panel?

Another test your vet may recommend is a chemistry panel, which tells them about kidney and liver health and electrolyte, blood glucose levels and protein levels in pets. This test will indicate elevations in blood urea nitrogen (BUN) and creatinine may indicate kidney disease or may also be elevated in dehydrated pets.

The chemistry panel will also give liver values (alkaline phosphatase), which can be elevated in older pets as a normal result of aging. Elevations in alkaline phosphatase (ALP) may also be seen in pets taking oral steroids, pets with liver or bone disease and young, growing pets. Alanine transaminase (ALT), on the other hand, is a liver value that, when elevated, can indicate ongoing liver damage.

Elevated glucose levels may show up on the blood chemistry panel if your dog or cat is diabetic. Occasionally, glucose is mildly elevated due to stress, which is one of the reasons it’s so important for your vet to know a pet’s normal levels.

Total protein levels are decreased in animals with poor nutrition or diseases that lead to protein loss, such as kidney or intestinal disease. Protein levels are elevated in dehydrated pets, those with some chronic infections and in some cases of leukemia.

Electrolyte imbalances will show up on a blood chemistry panel and can be life-threatening. Usually, changes are due to a variety of conditions, from vomiting to endocrine diseases to intestinal parasites.

Thyroid levels in dogs and cats

Baseline thyroid levels will let your veterinarian know if your pet has an underlying thyroid condition. Older cats are prone to overactive thyroids (hyperthyroidism), while older dogs have the opposite problem — sluggish thyroids, which lead to hypothyroidism. With regular testing, your veterinarian can tell if and when your pet develops a problem. 

How often should a pet have blood work done?

Senior pets should have blood work performed at least once a year and when they are battling systemic illness. Obtaining baseline levels will help your veterinarian stay on top of changes and prevent you both from being behind should an illness arise.

“The good news for pet parents is that most veterinary laboratories can return results in 24-48 hours for routine blood work,” Dr. Diehl says. “There are special tests, however, that take several days to even a few weeks to get results.”

You should always work with your veterinarian when it comes to running a pet’s blood work. If you suspect your pet might have an underlying problem, you should contact your vet right away.

The Dig, Fetch's expert-backed editorial, answers all of the questions you forget to ask your vet or are too embarrassed to ask at the dog park. We help make sure you and your best friend have more good days, but we’re there on bad days, too.

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