Blood Work for Dogs and Cats

Angela Beal, DVM, FFCP
By Angela Beal, DVM, FFCP on Apr. 29, 2024
A vet holds a dog and cat.

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Blood work for dogs and cats is a valuable diagnostic tool veterinarians use to check your pet’s overall health, find disease, and watch how disease changes.

These tests are important for healthy and sick pets because they can help your veterinarian track your pet’s health and figure out the right treatment or management strategy if something abnormal is found.

What Is Blood Work for Dogs and Cats?

Blood work for dogs and cats is done during your pet’s annual or biannual wellness visit to screen them for disease, while other specific tests are done if your pet is sick or injured. Blood tests are common diagnostic screenings veterinarians use to check dogs and cats, and they are relatively simple and noninvasive.

If your pet needs a blood test, a veterinary professional will put a sterile needle into your pet’s vein, usually in a limb or their neck, and draw the amount of blood needed.

Another team member will typically help hold your pet for the procedure and apply pressure to the puncture site after the blood draw to prevent a hematoma—a solid swelling of clotted blood within the tissues.

Types of Blood Work for Dogs and Cats

Blood work for dogs and cats measures substances in the blood such as cells, proteins, hormones, chemicals, minerals, and electrolytes.

Depending on your pet’s condition, your veterinarian may recommend your pet have one or more of these blood tests:

  • Complete blood count (CBC)— A CBC checks your pet’s red blood cells (RBCs), white blood cells (WBCs), and platelets to find conditions such as dehydration, infection, and anemia.

  • Biochemistry profile— A biochemistry profile checks your pet’s organ function, measures electrolyte levels, and finds certain enzyme levels.

  • Heartworm test— A heartworm test shows if your pet has heartworm disease and can also find certain tick-borne illnesses such as Lyme disease.

  • Thyroid panel— A thyroid panel checks your pet’s thyroid function. Hypothyroidism, caused by underproduction of thyroid hormone by the thyroid gland, and hyperthyroidism, caused by overproduction of thyroid hormone, are common in dogs and cats.

  • Cancer screening—A blood test is available to find some common cancers in dogs.

  • Genetic testing— Blood tests can figure out if your pet has a high risk for certain genetic conditions.

  • Gastrointestinal (GI) panel— A GI panel tests for conditions such as primary GI diseases, pancreatitis, and exocrine pancreatic insufficiency (EPI).

  • Allergy testing— Blood tests are also available to help show the environmental substances that may be causing a pet’s allergy symptoms.

Anatomy of a Vein in Dogs and Cats

In blood work for dogs and cats, veins are blood vessels that collect blood that doesn’t have much oxygen from around the body and return it to the heart. These vessels hold about 75% of a pet’s blood.

Veins are preferred to arteries for drawing blood because they are closer to the skin surface, making them easier to access.

In addition, veins have thinner walls and fewer nerves than arteries, so they are easier to poke through and don’t cause as much pain as an arterial puncture does. Veins also have lower blood pressure than arteries, and bleeding is easier to stop after a vein is poked as compared with an artery.

Why Would a Dog or Cat Need Blood Work?

Blood work for dogs and cats is helpful in many situations. Your veterinarian may recommend blood work for your cat or dog for one or more of the following reasons:

  • Wellness screening—Pets are excellent at hiding illness, and annual blood tests, such as a CBC and biochemistry panel, help find conditions in the early stages when they are easier to manage.

  • Parasite exposure—Annual screening blood tests are helpful to check for heartworm disease and tick-borne illnesses.

  • Sickness—If your pet is sick, blood work can help figure out the cause and allow your veterinarian to make the right treatment plan.

  • Injury—For pets who have significant trauma, such as being hit by a car, blood work is needed to figure out what treatment can stabilize their condition.

  • Anesthesia—Blood work is needed before a pet has anesthesia to make sure they are healthy enough for a procedure.

  • High-risk pets—If your pet’s breed is predisposed to a certain disease, blood work can show if they are likely to develop the condition, which helps your veterinarian start management strategies and keep an eye on them.

Benefits of Blood Work for Dogs and Cats

Blood work for sick and injured pets helps your veterinarian diagnose and treat their condition. Screening tests can help you and your pet by:

  • Setting a baseline for your pet’s normal values

  • Providing peace of mind that your pet is healthy

  • Tracking changes in your pet’s values from year to year

  • Helping find underlying health problems in the early stages

  • Helping prevent veterinary emergencies caused by underlying health conditions

Cost of Blood Work for Dogs and Cats

Special blood tests vary greatly in price, but routine blood work, including a CBC and biochemistry panel, typically costs $100 to $200 for dogs and cats.

Heartworm tests usually cost $35 to $75 and a thyroid panel ranges from $50 to $150.

Preparation for Blood Work for Dogs and Cats

Ask your veterinarian if you should prepare for blood work for dogs and cats. To prepare your pet for a blood test, your veterinarian may recommend the following:

  • Fasting—In some cases, you must withhold food for six to 12 hours so that fat droplets (lipemia) don’t interfere with the results.

  • Providing water—Ensure your pet has access to fresh, clean water to prevent dehydration. Even mild dehydration can skew blood work results.

  • Avoiding strenuous exercise—Tiring physical activity can change some blood work values, so make sure your pet stays calm before their blood draw.

  • Minimizing stress—Stress can affect your pet’s blood test results, so lower your pet’s stress by keeping them as calm as possible. Suggestions include keeping your dog leashed, keeping your cat in their carrier, bringing high-value treats, and waiting in the car until your veterinarian is ready for your pet. Your veterinarian may also recommend calming supplements.

  • Following other directions—For specific tests, your veterinarian may provide instructions such as giving a medication beforehand. Make sure you follow these directions carefully, so your pet’s blood work results are correct.

Complications of Blood Work for Dogs and Cats

Complications from blood work for dogs and cats aren’t common but may happen, especially if your pet is wiggly or nervous during the blood draw procedure.

Possible complications include:

  • Continued bleeding

  • Swelling

  • Bruising

  • Pain

  • Scarring around the vein

If your pet continues to bleed, keep pressure on the area until the bleeding stops. Any bruising, swelling, or pain should clear up in a few days.

If scarring around the vein happens, veterinary professionals may have a hard time using the vein for future blood draws.

Blood Work for Dogs and Cats FAQs

What does a full blood panel show for cats?

A full blood panel for a cat shows the cat’s electrolyte and mineral levels, enzymes showing liver and kidney function, and glucose and protein levels.

What does a full blood panel show for dogs?

A full blood panel for a dog is like a cat’s full blood panel, but some veterinary practices also include the dog’s heartworm status.

Do dogs really need annual blood work?

Yes. Annual blood work is an important part of your dog’s health care plan. Blood work for dogs allows your veterinarian to set a normal baseline for your pup and helps them find conditions in the early stages, when they are easier to manage.

Angela Beal, DVM, FFCP


Angela Beal, DVM, FFCP


Angela Beal is a veterinarian in Columbus, Ohio, who loves helping pet owners provide the best possible care for their beloved companions....

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