Every time I hand a client their dog's blood work results, clinical practice reveals the same expression: a mixture of concern and confusion. Pages of numbers, abbreviations, and reference ranges that mean little without context. Understanding your dog's blood panel is one of the most empowering things you can do as a pet owner, especially as your dog ages.
The Complete Blood Count (CBC)
The CBC evaluates the cellular components of your dog's blood:
Red Blood Cells (RBC) and Related Values
- RBC count, hemoglobin, and hematocrit: These measure your dog's oxygen-carrying capacity. Low values indicate anemia, which in senior dogs can result from chronic kidney disease, internal bleeding, immune-mediated conditions, or bone marrow issues.
- MCV and MCHC: These describe red blood cell size and hemoglobin concentration. They help a qualified professional determine the type and likely cause of anemia.
- Reticulocyte count: Measures immature red blood cells. A high count suggests the bone marrow is actively producing new cells (regenerative anemia). A low count in the face of anemia (non-regenerative) is more concerning.
White Blood Cells (WBC)
- Total WBC count: Elevated levels may indicate infection, inflammation, stress, or rarely, leukemia. Low levels can suggest immune suppression.
- Neutrophils: The first responders to bacterial infection. Elevated neutrophils are the most common sign of infection on blood work.
- Lymphocytes: Important for immune memory and viral defense. Chronically elevated or depressed levels warrant investigation.
- Eosinophils: Elevated in allergic conditions and parasitic infections.
Platelets
These are essential for blood clotting. Low platelets can indicate immune-mediated destruction, bone marrow issues, or certain infections (like tick-borne diseases, which are important to rule out in senior dogs in endemic areas).
The Chemistry Panel
Kidney Values
- BUN (Blood Urea Nitrogen): A byproduct of protein metabolism filtered by the kidneys. Elevated levels can indicate kidney dysfunction, dehydration, or high-protein diets.
- Creatinine: A more specific marker of kidney function than BUN. Elevated creatinine almost always indicates reduced kidney filtration.
- SDMA (Symmetric Dimethylarginine): This newer marker can detect kidney changes earlier than BUN or creatinine, often when only 25 to 40% of function has been lost. I consider SDMA essential for senior screening.
- Phosphorus: Rises as kidney function declines and contributes to further kidney damage. Monitoring and managing phosphorus is a key part of kidney disease management.
Liver Values
- ALT (Alanine Aminotransferase): The most liver-specific enzyme. Elevation indicates liver cell damage, though it doesn't specify the cause.
- ALP (Alkaline Phosphatase): Can be elevated from liver disease, bone disease, Cushing's disease, or certain medications (especially steroids). ALP tends to rise with age in many dogs, so mild elevations in seniors need to be interpreted carefully.
- Bilirubin: Elevated levels can indicate liver disease or red blood cell destruction.
- Albumin: Produced by the liver, low albumin can indicate liver disease, kidney protein loss, or intestinal disease.
Metabolic Values
- Glucose: Elevated levels may indicate diabetes or stress. Consistently low levels warrant investigation for insulin-producing tumors or liver disease.
- Calcium: Elevated calcium can be an early sign of certain cancers (especially lymphoma and anal gland carcinoma) and should always be investigated in senior dogs.
- Total protein and globulin: Elevated globulins can indicate chronic inflammation, infection, or immune stimulation.
The Thyroid Panel
Hypothyroidism is common in middle-aged and senior dogs. The key test is Total T4, with Free T4 used for confirmation. Classic symptoms include weight gain, lethargy, coat changes, and cold intolerance. Treatment with thyroid supplementation is usually straightforward and can dramatically improve quality of life.
How to Read Your Dog's Results
Three principles will help you make sense of any blood panel:
- Look at trends, not single values. A value that's high-normal and trending upward over three panels is more concerning than a mildly elevated value that's been stable for years.
- Context matters. Dehydration, recent meals, medications, and stress can all affect results. a qualified professional interprets numbers in the context of your dog's overall clinical picture.
- Ask questions. Never leave an appointment without understanding what the results mean for your specific dog. Good canine health professionals welcome questions and want you to be an informed partner in your dog's care.
Keep copies of all blood work results. Create a simple tracking sheet with key values and dates. This personal health record becomes invaluable as your dog ages and you accumulate data points that reveal meaningful trends.
Key Takeaways
- The CBC evaluates blood cells (red, white, platelets) and can reveal anemia, infection, inflammation, and clotting issues.
- Chemistry panel kidney values (BUN, creatinine, SDMA) are critical for early detection of kidney disease in senior dogs.
- Liver enzymes (ALT, ALP) indicate liver health but must be interpreted in clinical context, as mild ALP elevations are common in aging dogs.
- Thyroid testing is important for senior dogs, as hypothyroidism is common and highly treatable.
- Track trends across multiple panels rather than focusing on single values. Keep copies of all results and consult a qualified professional to explain any changes.
