Pre-Anesthetic Blood Tests

What does preanesthetic bloodwork assess?

While the exact biochemical parameters measured in preanesthetic bloodwork vary, depending on the particular bloodwork panel your veterinarian recommends, preanesthetic bloodwork typically involves two primary components.  These components are the CBC (Complete Blood Count) and a serum biochemistry.  These tests provide valuable information about your pet’s internal health status.

CBC (Complete Blood Count):

A complete blood count assesses the cells that are present in your pet’s blood.  Abnormalities in your pet’s cell counts may indicate an underlying disease and affect your pet’s surgical/anesthetic risks and recovery.

A complete blood count specifically looks at three types of cells that are found in the blood:

  • Red blood cells: these cells carry oxygen through the blood to your pet’s tissues. A CBC assesses the quantity, shape and hemoglobin content of your pet’s red blood cells. These tests detect a number of diseases, including anemia (low red blood cells) and polycythemia (elevated red blood cells).
  • White blood cells: these cells typically respond to inflammation and infection. A CBC not only measures your pet’s overall white blood cell count, but also provides separate counts for each unique type of white blood cell. Elevated white blood cells counts often indicate infection or inflammation; the specific white blood cell type that is abnormally elevated can often provide additional information about a possible diagnosis. Abnormally low white blood cells counts may indicate a more serious infection or possible immunodeficiency.  Less commonly, dramatic white blood cell count abnormalities may indicate cancer.
  • Platelets: platelets are responsible for blood clotting. A low platelet count suggests that your pet may be at greater risk of excessive blood loss during surgery.

Serum biochemistry:

The serum biochemistry examines levels of a number of chemicals in the blood associated with organ function.  The exact parameters that are checked in a blood panel will vary depending on the particular panel your veterinarian recommends; young, healthy pets may receive a smaller biochemistry panel than seniors. In general, a serum biochemistry will include values that assess your pet’s liver, kidneys, blood glucose, serum proteins and possibly other parameters.

  • Liver function: is assessed through a number of values on the serum biochemistry. These values include alkaline phosphatase (ALP), alanine transferase (ALT) and can include others (ie. AST, GGT, total bilirubin). Elevations in these values may suggest an increased risk of liver disease in your pet.
  • Kidney function: is assessed by measuring the blood urea nitrogen (BUN) and creatinine. Both of these substances are normally cleared by the kidney. Increased levels of BUN and creatinine suggest that they are not being effectively cleared by the kidney, due to dehydration or kidney disease.
  • Glucose: is a measure of the sugar in the blood. Dramatically elevated blood glucose levels may indicate diabetes.
  • Serum proteins: include albumin (ALB), globulin (GLOB) and total protein (TP). Low protein levels are associated with a number of medical conditions. Pets with low protein levels may experience delayed post-surgical healing.  Elevated serum protein levels may indicate dehydration.
  • Electrolytes: such as potassium (K), sodium (Na) and chloride (Cl) may be tested and may become increased or decreased with various disease states that may affect surgical healing or suitability for anesthesia.

Why is Preanesthetic Bloodwork Recommended?

Preanesthetic bloodwork is typically recommended for most animals that are undergoing anesthesia.  This allows your veterinarian to assess your pet’s overall health, ensuring that your pet is a good candidate for anesthesia.  If preanesthetic bloodwork shows any abnormalities, these can be addressed by making any necessary adjustments to your pet’s treatment plan.

For geriatric or ill pets, additional blood tests, electrocardiograms, or x-rays may be recommended before surgery as well. If serious problems are detected, surgery can be postponed until the problem is corrected. 

Along with the bloodwork we perform a thorough physical exam on your pet before administering anesthetics, this is to ensure that a fever or other illness won’t be a problem. We also adjust the amount and type of anesthetic used depending on the age and health of your pet. We have advanced anesthesia monitoring equipment and will make surgery as safe and efficient as possible. 

How might the test results affect my pet’s treatment?

If your veterinarian finds abnormalities in your pet’s preanesthetic bloodwork, there are several potential outcomes.

Some abnormalities are mild and unlikely to be clinically relevant.  For example, a white blood cell count that is just marginally above the normal range, in the absence of clinical signs, may be an indication of stress and not of any underlying disease.

A marginally elevated blood glucose without other abnormalities may also be seen with stress.  If your pet has a very mild elevation, your veterinarian may proceed with anesthesia without any further testing or interventions.  In some cases, your veterinarian may recommend rechecking the value in the future, to ensure that more significant abnormalities do not develop, even if the elevation does not appear to be significant at the time of testing.

In some cases, preanesthetic bloodwork detects abnormalities that can be corrected prior to anesthesia.  For example, if your pet’s preanesthetic bloodwork indicates mild dehydration, your veterinarian may administer intravenous fluids prior to anesthesia.  This allows your pet to be as medically stable as possible prior to undergoing anesthesia.

In other cases, however, more significant abnormalities might be detected on preanesthetic bloodwork.  In these cases, your veterinarian may recommend postponing surgery until additional testing or treatment can be performed. Examples of situations where this may occur include anemia, elevated liver or kidney values, or diabetes.  In the case of significant bloodwork abnormalities, postponing surgery until the pet’s condition can be thoroughly diagnosed and addressed helps maximize the chances of a safe anesthetic procedure and smooth recovery.

Contact Us

Phone: 802-888-7776

Text: 802-888-7776

Email: [email protected]

Fax: 802-888-4325


147 Stancliff rd

Morrisville, VT 05661

Hours of Operations
Monday8:00am – 5:00pm
Tuesday8:00am – 5:00pm
Wednesday8:00am – 5:00pm
Thursday8:00am – 5:00pm
Friday8:00am – 5:00pm
Saturday8:00am – 12:00pm

Closed Sundays and major holidays, at which times we are still available for emergencies.


We are available for emergencies 24/7 for existing clients. If your pet is having an emergency please call 802-888-7776. You will be prompted on how to reach a doctor.