Senior Care · Updated 2026-03-26

Senior Dog Bloodwork, Explained: What The Numbers Mean And Which Ones To Watch

A plain-language walkthrough of a senior dog's wellness bloodwork — CBC, chem panel, thyroid, urinalysis — and what trends to watch over years.

Why senior bloodwork matters more than it seems

By the time a senior dog shows symptoms of kidney disease, roughly two-thirds of kidney function is already gone. The same compression applies to thyroid disease, early Cushing's, and many cancers. Annual (and then biannual) bloodwork is the way to catch the slope before the cliff. It costs $150–$350 per year for the standard senior panel and is, in our experience, the single highest-return spend in older-dog care.

This guide explains what shows up on the panel, what moves in the wrong direction mean, and how to work with your vet to track trends rather than individual numbers.

What's on a senior panel

A typical senior workup includes:

• Complete Blood Count (CBC): red cells, white cells, and platelets
• Chemistry panel: liver enzymes, kidney values, electrolytes, proteins, glucose
• Thyroid: total T4, sometimes free T4 by equilibrium dialysis
• Urinalysis: concentration, protein, sediment
• Sometimes: pancreatic lipase, bile acids, blood pressure

CBC — the cellular snapshot

Red blood cell measures

PCV (packed cell volume) and hematocrit below 37% in a dog suggest anemia. Causes range from chronic disease to blood loss to marrow suppression. A gradually declining PCV over three years, even if still in range, is a flag.

White blood cells

Total white count and differential. A high neutrophil count with low lymphocytes ("stress leukogram") often means cortisol, not necessarily disease. Eosinophils trending up suggest allergic or parasitic processes.

Platelets

Below 100,000/μL is low and should be retested — lab artifacts are common. Below 50,000 is clinically meaningful.

Chemistry panel — the body's accountants

Kidney values

BUN (urea) and creatinine are the classic markers. SDMA is a newer, more sensitive marker of early kidney decline, picking up dysfunction at roughly 40% loss rather than 65%. A creatinine trending upward over two annual visits, even if still "in reference range," is meaningful. Ask your vet to show you the trendline — a PDF across three years is more informative than one data point.

Liver enzymes

ALT, ALP, AST, GGT. ALP is elevated in many older dogs for benign reasons (steroid response, nodular hyperplasia). A persistently elevated ALT is more concerning. Liver values rarely tell a complete story alone; they flag the need for bile acids testing or imaging.

Electrolytes

Sodium, potassium, chloride. Sudden changes (hyponatremia, hyperkalemia) raise flags about Addison's disease or kidney issues. Bicarbonate changes flag acid-base disturbances.

Proteins and glucose

Total protein, albumin, globulin. Low albumin with high globulin is a pattern that sends the workup in specific directions. Glucose elevations — especially persistent — need a second test and possibly fructosamine to rule out diabetes.

Thyroid — common and commonly missed

Hypothyroidism in dogs is most often diagnosed in middle-aged to older large-breed dogs. Total T4 alone is not definitive; a free T4 by equilibrium dialysis plus TSH is the confirming panel. Classic signs — weight gain, lethargy, skin changes, cold intolerance — come on so gradually that owners describe them as "he's just getting older." A T4 in the low-normal range in a dog with symptoms is worth a free T4 follow-up.

Hyperthyroidism in dogs is rare (it's primarily a cat disease). Don't confuse the two.

Urinalysis — the under-valued test

A first-morning urine, caught cleanly, tells you more than almost any single blood value. Specific gravity is the concentration. A dog with normal kidneys concentrates urine above 1.030 when dehydrated; a dog who cannot concentrate above 1.020 is losing function. Protein in the urine, in the absence of infection, is a nephropathy flag — run a urine protein:creatinine ratio (UPC) to quantify.

The trend matters more than the snapshot

A single set of numbers in mid-reference range is a data point. Three sets of numbers, with your dog's creatinine climbing from 1.1 to 1.4 to 1.6 across three years, is a kidney conversation. Ask your vet for a printed trend graph at your next visit. If they don't usually do this, ask anyway — the clinic's software almost certainly supports it.

The add-ons worth considering

• Blood pressure: hypertension is silent in dogs but common with kidney disease. A baseline reading is useful.
• Bile acids test: the right follow-up to persistent liver value elevations when ultrasound hasn't shown structural change.
• Echocardiogram: for large-breed dogs with any cardiac breed predisposition (Dobermans, Great Danes, Boxers), a baseline echo is worth the one-time cost.
• Abdominal ultrasound: once in the senior years for dogs in high-risk categories — early masses are sometimes found incidentally.

What I would not panic about

• A slightly elevated ALP in an otherwise healthy senior
• A single out-of-range value without pattern
• A normal T4 in a dog with non-specific lethargy — retest if symptoms persist; don't start medication on a single equivocal reading

Where to go next

Pair this with our choosing a vet guide — a clinic that prints trend graphs, answers questions, and doesn't push products is the clinic you want running these panels. For financial planning, the pet insurance guide covers what is and isn't covered for senior wellness testing.

The one habit to start

Ask for a printed copy of every lab report at the time of the visit. Keep a folder. When a future vet asks "what were her kidney values two years ago?" you'll be the owner who hands over the printout. That's the owner senior dogs deserve.