Hannah Zulueta The Window Between the First Abnormal Number and the Diagnosis
Most guidance says start the diet at Stage 2. The dogs in the research did not wait that long.
The vet says the number is elevated, hands you a recheck date two to four weeks out, and sends you home to wait. A single blood draw needs a second look before either of you can trust it.
A real diagnosis takes three draws.
One elevated creatinine or SDMA raises a question. It could be the kidney. It could be a big meal, a hot car ride, or a dog who did not drink enough water that morning. Three draws answer it: the first draw that raises the question, a second draw done right to rule out the obvious impostors, and a third draw two to four weeks later to prove the finding holds. Only then does staging, and the diet conversation, actually begin.
Why It Takes Three Draws to Get There
Chronic kidney disease means the kidney has abnormalities in structure or function that have been present for at least three months, with real effects on the body (Polzin, 2011). One abnormal lab value does not confirm that on its own. It has to persist, or come with other evidence, before it counts.
Here is what actually happens between the first flagged lab value and an IRIS stage landing on your dog’s chart.
Once that third draw confirms the finding, most dogs land at Stage 1 or Stage 2. And that is exactly where the real question in this article begins.
The Test That Sees Earlier
Early kidney disease in a dog can be present for months without a single visible sign. Your dog eats, plays, and acts completely normal while the numbers underneath are already shifting. For decades, BUN and creatinine were the only routine window into kidney function, and both share the same blind spot. Neither one rises in a meaningful way until roughly three quarters of kidney function is already gone (Polzin, 2011). SDMA changed that math. It can flag a problem with roughly 25 to 40 percent of kidney function lost, often well before creatinine ever moves, and before your dog ever looks sick (Nabity et al., 2015; Hall et al., 2016).
That gap is the difference between catching this while there is still kidney reserve to protect, and catching it after the reserve is already spent.
Why the First Number Doesn’t Always Mean What It Looks Like
An elevated BUN or creatinine can come from two very different places. One is the kidney tissue itself losing function. The other is simply reduced blood flow reaching the kidney, from dehydration, a big meal, heat, or stress, with the tissue itself still intact (Polzin, 2011). This is called a pre-renal pattern, and it is the reason the second draw carries so much weight.
Vets read the blood values alongside urine concentration for exactly this reason. A dog with elevated creatinine and well concentrated urine likely has a hydration problem, and the number should improve once that is corrected. A dog with elevated creatinine and dilute urine has a kidney problem, and that is the one that gets staged and managed. See Decoding the Urinalysis and Acute vs. Chronic Kidney Disease for how these two pictures get told apart.
What the Stage Actually Buys You
Dogs diagnosed at Stage 1 or 2 have measurably more room than dogs diagnosed at Stage 3 or 4, where survival is typically counted in months rather than years (O’Neill et al., 2013). Diet is one of the few levers that actually moves that gap. In a study following dogs with Stage 2 to 3 chronic kidney disease, those fed a renal diet survived a median of 594 days. Dogs fed a regular maintenance diet survived a median of 188 days (Jacob et al., 2002).
That is more than a year of life from a bag of food.
Catching this early buys time: time to adjust the food, time to watch a trend instead of reacting to one number, and time to manage anything else your dog is carrying before the kidney is doing all of the compensating by itself.
So Should You Wait for Stage 2?
Most nutritional guidance still draws the starting line at Stage 2, once creatinine crosses roughly 1.4 mg/dL (Hall et al., 2018). Below that line, a Stage 1 dog with no azotemia yet is often told to wait and recheck. One study asked the obvious follow up question directly: does a dog diagnosed at Stage 1, before creatinine ever crosses into azotemia, actually benefit from starting sooner?
Thirty six dogs with confirmed Stage 1 disease, some with dilute urine, some with mild proteinuria, were transitioned onto a therapeutic renal food and followed for a year. Creatinine, BUN, and SDMA all dropped from baseline by three months and stayed down at twelve months. Owners reported better coat quality and a visibly better quality of life (Hall et al., 2018).
The dogs in that study started at Stage 1. Once your dog’s third draw has confirmed the finding, the research argues for doing the same. See What to Feed a Dog With CKD for the sorting question that comes next, or Just Diagnosed: Now What if you are still in the early days of all of this.
What I Would Do If This Happened to Me
Last spring, Orbit gave me a live version of everything above. She inhaled a foxtail while we were breaking down camp, and that story got its own article. What that piece leaves out is the number that showed up on her labwork the same week.
We had just come off a hot, dry camping trip. She was not fasted when we brought her in, and she was not particularly hydrated either. Her SDMA came back slightly elevated. My vet’s read matched everything above: recheck in thirty days, done properly this time, before either of us decided anything. I agreed with him.
I did not change her food. She was not azotemic, and the finding was fresh and unconfirmed. I did not want to build a new diet plan around a number that might simply resolve once she was rested and drinking normally again. But she is ten, and I was not going to sit on my hands for thirty days either. I started her on Rehmannia Eight, a gentle Kidney Yang tonic, while we waited out the recheck.
Thirty days later, she went back fasted, hydrated, and well rested. Her SDMA was normal. Every value was normal.
I still do not know for certain that the first number was only the heat and the unfasted draw. I was never going to know that from one draw. That is the entire point of this article. What I did in the meantime was small, supportive, and reversible: I gave her body a gentle hand while we waited for real information, and I did not restrict her diet on the strength of a single unconfirmed number.
A Few More Questions
How many blood draws does it actually take to diagnose kidney disease in a dog?
Typically three: the draw that first flags an elevated creatinine, BUN, or SDMA, a second draw done fasted and hydrated to rule out dehydration or a recent meal, and a third draw two to four weeks later to confirm the finding holds. See Labwork Frequency by Stage and The IRIS Stages for what monitoring looks like once a stage is confirmed.
Can heat, stress, or an unfasted blood draw cause a false elevated SDMA in dogs?
Yes. Dehydration, a recent meal, exercise, and heat can all push BUN, creatinine, and SDMA higher without any real change in kidney function. This is exactly why a second draw done fasted, hydrated, and rested comes before anything gets diagnosed as kidney disease. See Reading the Bloodwork for what each value is actually measuring.
Should I start a kidney diet at Stage 1, or wait until Stage 2?
The research argues against waiting. A twelve month trial of Stage 1 dogs, none of them yet azotemic, found that starting a therapeutic renal food early lowered creatinine, BUN, and SDMA, and the improvement held for the full year (Hall et al., 2018). See What to Feed a Dog With CKD for the sorting question that comes next.
What is Rehmannia Eight used for in early kidney disease?
Rehmannia Eight (Jin Gui Shen Qi Wan) is a classical Kidney Yang tonic, sometimes used to gently support an aging kidney while labwork is being confirmed or monitored. It is not a substitute for diagnosis or diet, and whether it fits a particular dog depends on that dog’s individual pattern. See Rehmannia Six vs Eight for how the two classical formulas differ.
What is the difference between acute and chronic kidney disease in dogs?
Acute kidney injury comes on fast, often from a specific cause, and can sometimes fully resolve. Chronic kidney disease has been present for months or longer and is generally not reversible, though it can be slowed. The same blood panel can look nearly identical in both until the history and the urine tell the two apart. See Acute vs. Chronic Kidney Disease for how that distinction actually gets made.
The Wait Protects the Sample
Three draws exist to rule out a bad sample, not to buy time once a real diagnosis is in hand. The dogs in the research above started on a renal diet the moment Stage 1 was confirmed. Once your dog’s third draw says the same thing, there is no clinical reason to wait any longer than they did.
Build the Stage 1 Bowl With MeHall, J. A., Yerramilli, M., Obare, E., Yerramilli, M., Almes, K., & Jewell, D. E. (2016). Serum concentrations of symmetric dimethylarginine and creatinine in dogs with naturally occurring chronic kidney disease. Journal of Veterinary Internal Medicine, 30(3), 794-802. https://doi.org/10.1111/jvim.13942
Hall, J. A., Fritsch, D. A., Yerramilli, M., Obare, E., Yerramilli, M., & Jewell, D. E. (2018). A longitudinal study on the acceptance and effects of a therapeutic renal food in pet dogs with IRIS-Stage 1 chronic kidney disease. Journal of Animal Physiology and Animal Nutrition, 102(1), 297-307. https://doi.org/10.1111/jpn.12692
International Renal Interest Society. (2026). IRIS staging system. https://www.iris-kidney.com/iris-staging-system
Jacob, F., Polzin, D. J., Osborne, C. A., et al. (2002). Clinical evaluation of dietary modification for treatment of spontaneous chronic renal failure in dogs. Journal of the American Veterinary Medical Association, 220(8), 1163-1170.
Nabity, M. B., Lees, G. E., Boggess, M. M., Yerramilli, M., Obare, E., Yerramilli, M., Rakitin, A., Hu, X., & Aguiar, J. (2015). Symmetric dimethylarginine assay validation, stability, and evaluation as a marker for the early detection of chronic kidney disease in dogs. Journal of Veterinary Internal Medicine, 29(4), 1036-1044. https://doi.org/10.1111/jvim.12835
O’Neill, D. G., Elliott, J., Church, D. B., McGreevy, P. D., Thomson, P. C., & Brodbelt, D. C. (2013). Chronic kidney disease in dogs in UK veterinary practices: Prevalence, risk factors, and survival. Journal of Veterinary Internal Medicine, 27(4), 814-821. https://doi.org/10.1111/jvim.12090
Polzin, D. J. (2011). Chronic kidney disease in small animals. Veterinary Clinics of North America: Small Animal Practice, 41(1), 15-30. https://doi.org/10.1016/j.cvsm.2010.09.004
