OldieThe results come back, and there it is: a line of numbers, and one of them is flagged. High, low, an arrow, a bit of bold type. Most of us read the flag before we read anything else, and our stomachs drop a little.
This post looks at how those flags get drawn in the first place, and at what veterinary sources say about testing older dogs. It isn't about what any result means for your dog. Only your vet can say that.
Why older dogs get tested at all
The American Animal Hospital Association's canine life stage guidelines list, for senior dogs, a blood count, a chemistry panel and a urinalysis, each every 6 to 12 months1. Those are the guidelines' own recommendations for the group, and your vet may see your dog's situation differently.
So a lab report isn't a sign that something is wrong. For a senior dog it's often just the routine. A routine that repeats is also what makes a single page of numbers easier to read, because there's something to compare it with.
How a normal range gets drawn
The range printed beside each number is called a reference interval. Cornell University's Animal Health Diagnostic Center explains that its intervals are built so that they include about 95 percent of results from healthy animals. In its words, up to 5% of normal animals may have values that fall slightly outside the intervals for a given test2.
Read that twice. The line isn't drawn between healthy and sick. It's drawn so that a small slice of healthy animals land just outside it. A flag means a value fell outside the range. It doesn't tell us why.
More tests, more chances for a flag
The same Cornell page does the arithmetic on running many tests at once. It gives the chance of at least one slightly abnormal result in a normal animal as 1 minus 0.95 raised to the number of tests, and says that works out to 0.46 for 12 tests and 0.66 for 21 tests2.
A full chemistry panel runs a lot of tests. We read that as a reason a lone flag, on its own, is often less dramatic than it looks. We won't push it further than that, because a flag can also matter a great deal, and telling the two apart is the vet's job.
Where the range comes from matters too
Cornell also notes that its intervals were established with its own laboratory's equipment, methods and reagents, and are only valid for results from that laboratory2. It adds that they apply to adult animals2. In plain terms, a number from one lab and a number from another aren't always measured against the same yardstick. That's one more reason to keep the reports from the same place together and ask the vet to read them side by side.
Questions worth bringing to the vet
None of this is a way to interpret a report at home. These are ordinary questions, and your vet decides what any of it means.
- Which of these flagged values matter to you, and which do you expect to be a small step outside the range?
- How does this compare with last time? Can we look at the old report together?
- Is there anything about your dog's history, breed or medications that changes how you read it?
- Would you like to repeat anything, and when?
- What should we write down at home between now and the next visit?
Keep the dates and the reports together, in a place everyone caring for the dog can find. Oldie is a care tracker for senior dogs: medications, care tasks, vaccines and weight, shared with everyone in the household. More about Oldie.
A flagged number does deserve a conversation. It just doesn't deserve a verdict before the conversation has happened.
This post is general information only, not a diagnosis. Your vet knows your dog.
Questions, or a topic you'd like us to dig into next? Reach out any time: help@myoldie.com. We read everything.
Sources
- Diagnostic Testing for Each Life Stage. American Animal Hospital Association, 2019 Canine Life Stage Guidelines. Accessed 2026-11-02.
- Reference Intervals. Cornell University College of Veterinary Medicine, Animal Health Diagnostic Center, Clinical Pathology. Accessed 2026-11-02.
This is general information, not a diagnosis. Your vet knows your dog.