A Vet Tech Explained Senior Bloodwork to Me Like I Was Five

The woman in room two had highlighted her dog's bloodwork in three colors before she got out of the car. Yellow for every line with an H next to it, pink for the L's, green for the two she'd already looked up on her phone in our lot. The dog, Junie, fourteen, black lab, was on the floor working on a treat crumb somebody dropped near the scale. Junie was fine. Her owner's hands were not.

I've watched a version of that a few hundred times. The senior panel is the most upsetting piece of paper we hand anyone, and most of the upset is vocabulary. Nobody explains the columns. The machine flags anything outside a range with a letter that looks like a grade on a test, and then you take it home.

So here's what I say in the room while the doctor finishes up next door, and I'm putting it at the top because it's the whole point: a flagged number is a question, not an answer. I'm a technician. I don't diagnose, and neither should you, and I mean that kindly. What follows is vocabulary, so the eleven minutes you get with your vet go toward your actual question instead of toward somebody explaining what BUN stands for.

(Kelsey wrote that headline, not me. I've never explained anything to anyone like they were five. I've explained things slowly. There's a difference and I'll defend it.)

Why the paper looks worse than the dog

Reference ranges come from a pile of other dogs. Yours is not that pile. Plenty of healthy animals live their whole lives a hair outside a range on one value, and the flag is automatic.

No human looked at your dog and decided to put an H there.

Ranges move between labs, too. Our in-house analyzer and the send-out lab we use don't run the same numbers, so a value flagged in October and clean in March may not have budged at all.

What I actually want off a panel is a direction. One panel is a photograph; two panels a year apart start to say something. That's the argument for running boring wellness bloodwork on a healthy senior, which I know feels like paying $180 to be told nothing is wrong. You're paying for next year's comparison.

Junie was in that day because she'd started taking the stairs one at a time, one of those quiet changes people file under old age and mention on the way out the door. The bloodwork was routine. The highlighters were her owner's own idea.

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BUN and creatinine, the kidney-shaped questions

BUN is blood urea nitrogen. Protein gets broken down, urea is what's left over, kidneys clear it out. Creatinine comes out of muscle at a fairly steady rate and also leaves through the kidneys. They travel together, which is why they sit next to each other on the page.

Both climb when kidneys aren't clearing the way they used to. Both also climb when a dog is simply dry. A dog who threw up on the drive in, or ate a big meal an hour before the draw, can hand you a number that looks alarming and means she needs water and a do-over.

Creatinine has a wrinkle nobody mentions: it comes from muscle. A skinny, muscle-wasted fifteen-year-old can produce a creatinine that looks beautifully normal, because there's not much muscle left to make it. A thick-necked young shepherd can sit near the top of the range for life and be fine. The number means something different depending on the body it came out of.

So the question those two ask is: dry, or kidneys losing ground? A urine sample usually settles it faster and cheaper than another blood draw. Which is why we ask you to walk in carrying your dog's pee like a party favor.

The liver numbers people google at midnight

ALT is an enzyme that lives inside liver cells. When those cells are irritated or dying, ALT leaks into the blood: more leaking, higher number. It doesn't tell you why, and it doesn't tell you how well the liver is working. Irritation and function are separate questions printed on the same page.

ALP, alkaline phosphatase, causes more Sunday-night panic than anything else on the sheet. In dogs it comes from more than one place, including the biliary system and bone, and it climbs with steroids, including the dog's own cortisol. Older dogs run a mildly high ALP all the time. Sometimes it matters enormously, sometimes it's background noise for six years, and your vet is weighing it against the dog in front of them. The internet can't do that part.

Albumin, the one I read first

Albumin is a protein the liver makes. It holds fluid inside blood vessels. I look at it before anything else, which is a personal habit, not a protocol. Don't quote me to your vet as doctrine.