Hannah Zulueta Canine Nutrition / Kidney Disease
Reading the Bloodwork
You are holding a lab report full of abbreviations, and somebody circled two of them. Nobody translated. Tap the value you are staring at.
Creatinine
Muscle makes creatinine at a steady rate, every day, and healthy kidneys clear it. When clearance falls, creatinine rises. It is the backbone of staging.
Two honest caveats. It rises late, often after most of the filtering capacity is already gone. And it tracks muscle: a heavily muscled dog runs naturally higher, and a dog losing muscle to illness can show a falsely comforting number. That is why creatinine is never read alone.
SDMA
The newer marker. SDMA rises when roughly 40 percent of function is lost, where creatinine often waits until 75 percent. It also cares less about muscle, which makes it steadier in thin old dogs and in heavily muscled ones.
SDMA did not replace creatinine. The two are read together, and when they disagree, your vet looks at muscle mass and rechecks in a few weeks.
BUN, blood urea nitrogen
Urea is the leftover from protein digestion, and the kidney clears it. BUN rises with failing clearance, but it also rises with dehydration, with a recent meal, and with a high-protein bowl.
A fresh-fed dog often runs a BUN above the kibble-based reference range without anything being wrong. Useful for the picture, weak as a verdict.
Phosphorus
The mineral the failing kidney cannot spill, and the number with the strongest evidence behind managing it. The target tightens by stage.
This one is the first lever the bowl can pull, and it has its own room, phosphorus, binders, and the hidden additives.
Potassium
In kidney disease potassium can drift either direction: most dogs slowly waste it, and a smaller group cannot clear it and run high. Neither direction shows on the outside until late, and the two problems need opposite plans, which is why the number gets checked rather than guessed.
UPC, urine protein to creatinine
The blood tells you how the kidney is filtering. The urine tells you whether the filter is leaking, and a leak speeds the disease. Under 0.2 is clean, 0.2 to 0.5 is borderline, and above 0.5 is a leak worth acting on.
The one thing
One bad number on one hard day does not stage a dog. Trends, taken the same way every time, tell the truth.
Getting a sample the numbers can trust
The values are only as good as the draw, and the draw is something you control.
Morning, fasted+
Food raises creatinine and BUN for hours afterward, so a meal before the draw can nudge a borderline dog over a line that was never crossed. Fast for eight to twelve hours, easiest as a morning visit after a skipped breakfast. Water is always fine. Never withhold water from a kidney dog.
Skip the organ treats the day before+
Liver and kidney treats are concentrated protein, and a generous handful the night before a draw can push BUN and creatinine upward for no reason the kidney is responsible for.
Calm and hydrated+
Dehydration concentrates the blood and raises the kidney numbers on its own. Hard exercise right before a draw can do the same. A hot car ride and a stressed dog can move a borderline panel.
Same conditions, every time+
Same fasting window, same time of day, ideally the same laboratory. You are building a trend, and a trend is only readable when the samples are taken the same way.
What else can throw a test+
A hemolyzed sample, where red cells rupture in the tube and spill potassium, falsely raising it. Heavy muscle, which runs creatinine naturally high in some breeds, and muscle loss, which runs it deceptively low. Certain medications, which your vet will weigh. If a scary result arrives out of nowhere, ask whether the sample was clean before anyone acts on it.
The other half: urinalysis
The blood panel is half the picture. The urine is the other half, and it should be on the order at every kidney recheck, asked for by name.
Urine specific gravity
Specific gravity measures how concentrated the urine is, how much the kidney packed into the water it released. A healthy kidney conserves hard when the body needs water, producing concentrated urine. A failing kidney loses that ability early, so the urine runs watery and pale even when the body is trying hard to hold water.
Persistently dilute urine, sitting near the concentration of blood itself, is one of the earliest kidney signs there is, often moving before creatinine does. A first-morning sample tells this story best, since overnight is when a healthy kidney concentrates hardest.
Protein in the urine
The urinalysis screens for protein with a dipstick, and dipsticks are rough, prone to both false alarms and misses. A positive screen gets confirmed with the UPC ratio, the number from the tab above, and persistence across samples is what names a real leak.
The habit worth building: any time urine is tested, ask whether protein was checked, and if the screen was positive, ask for the UPC by number.
How the sample is taken
Skip the jar from home. Urine changes fast once it leaves the dog: crystals form or dissolve, cells break down, and bacteria multiply on the ride over, all of which can paint a false picture. A sample collected at the clinic is fresh, and when protein or infection is in question, the vet can draw urine directly from the bladder with a quick sterile needle, which gives the cleanest answer there is.
One test does not make the diagnosis
A single alarming panel is a reason to recheck, not a verdict. The staging system vets follow calls for the numbers to be confirmed on at least two occasions, in a stable, hydrated dog, with other causes ruled out. And chronic means chronic: the disease is defined by trouble that persists over months, not by one bad morning. If the first abnormal panel arrived on a sick day, ask about rechecking once your dog is stable before anyone names a stage.
Your vet reads this. You track it.
Everything on this page is so you can follow the conversation, not replace it. Interpreting a panel against your dog’s history, medications, hydration, and body condition is your veterinarian’s work, and the best outcomes come from a running dialogue: you bring the questions and the trends, your vet brings the interpretation and the plan. Bring every report home, keep them in one folder, and you are building the one record nobody else has: your dog’s own baseline, over time.
The labs are the boundaries. Your dog is the compass.
Bring me the numbers and the trends, and I will build the bowl that fits inside them.
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Hannah Zulueta obtained her Certificate in Canine Nutrition from CASI Institute. She is also studying for her Doctorate in Acupuncture, Traditional Chinese Medicine, and Herbalism from the esteemed Pacific College of Health and Medicine. If you’re as keenly interested in health for yourself, visit her website for human health: Satori Acupuncture and Herbs.
She resides in San Diego with her three dogs, Maggie, Orbit, and Mr. Higgins.
She is available for one on one consultations. She develops evidence-based recipes that meet both NRC and AAFCO nutritional standards while integrating the therapeutic food principles of Traditional Chinese Veterinary Medicine into her formulations.
Additionally, you can find her sharing free content on Instagram.
