Bloodwork · BUN
Elevated BUN Is Not Normal
A high number deserves investigation, not a shrug
For years, elevated Blood Urea Nitrogen has been accepted as normal in raw and home-cooked dogs, largely on the strength of a single old study. As a nutrition professional, I think it is time to challenge that, and to ask for better research.
Where I stand
This is the hill I will die on.
A high BUN is not just a quirk of fresh feeding. Time and again I have brought a dog’s BUN back into range with a carefully formulated diet, often within three to six months. Normalizing the number, instead of asking why it is high, can delay a conversation you should be having with your vet, and can hide early signs of something more.
Where the idea came from
Two studies, read closely
Tap each. What it found, and what it left out.
It compared 227 raw-fed dogs across BARF, popular, and custom raw diets against 75 kibble-fed dogs over nine months. BUN ran higher in every raw group, and the authors concluded that reference ranges for raw-fed dogs should be revised. I respect the researchers. But by today’s standards the study has real gaps.
- It cannot be found in PubMed or standard peer-reviewed databases.
- Basic design details are missing, and even the date is unclear, 2005 or 2015.
- No documented method for how dogs were chosen or monitored.
- The BARF diets studied differ from modern, refined raw formulations.
- No diet composition, no protein standardization, no look at bioavailability.
Some of the background here draws on HemoPet.
A second study looked at 37 dogs fed raw for a year or more, checking urine for microalbuminuria. Five tested positive, and the authors concluded raw did not cause protein leakage in most dogs. It left more questions than answers.
- 37 dogs is a small sample for population-level conclusions.
- Three positive cases, about 8% of the sample, were lost to follow-up.
- No control group, such as kibble-fed dogs, for comparison.
- No information on the dogs’ ages, and renal function changes with age.
- Two dogs had UTIs, which raises its own questions about screening and cause.
Why the number rises
From protein to BUN
Dogs draw energy from carbohydrates, fats, and protein. Carbs and fats burn cleanly. Protein is where it gets complex, because breaking it down makes ammonia, which is toxic, and the body has to convert and clear it.
BUN is that urea, measured in the blood. It climbs when there is more protein to process than the body needs, or when the kidneys are under stress. On fat, note that dogs use it well as a primary fuel, raw but never cooked. More on that in the Fat Factor.
A better early warning
Ask for SDMA, not just BUN
SDMA, symmetric dimethylarginine, catches kidney change far earlier than BUN or creatinine, and it is not thrown off by muscle mass or protein intake, which makes it more honest in a senior or lean dog. It helps separate a diet effect from real kidney stress. Ask for it alongside the bloodwork.
If the number is high
Test three times
Think beyond the kidneys
A high BUN can mean inflammation
An elevated BUN without obvious kidney dysfunction can be an early flag for inflammation elsewhere. Try not to get attached to a single data point. Look at the whole dog.
Gut
IBD, protein absorption trouble, a leaky gut barrier, microbiome imbalance, food sensitivities, malabsorption, and the toll of chronic diarrhea can all show up in the numbers.
Metabolic
Early metabolic syndrome, insulin resistance, oxidative stress, mitochondrial dysfunction, and protein-handling problems can drive low-grade inflammation.
Immune and allergies
Developing autoimmune conditions, chronic low-grade inflammation, environmental and food allergies, skin inflammation, and recurring ear infections all belong in the picture.
Other systems
Endocrine imbalances, liver stress before dysfunction shows, cardiovascular strain, joint inflammation, and neurological inflammation can all sit underneath a high reading.
The gap in a bag
Commercial renal diets don’t catch everything
Prescription and commercial renal diets are built to a general template. They lower phosphorus and protein to a standard, which helps, but they cannot account for what is happening in your specific dog.
Potassium is a clear example. I recently worked with a dog whose potassium ran high. That dog needed binders and a diet formulated to limit potassium, something a commercial renal diet simply does not do. And it cuts the other way too, since some kidney dogs run low on potassium instead. The point is the same: you have to formulate to the actual numbers on your dog’s panel, not to an average.
When conditions collide
Competing goals in one bowl
Tap a condition to see where it pulls against the kidney plan.
Low fat versus the need for energy.
Pancreatitis calls for a low-fat diet. But a kidney dog often leans on fat for calories, precisely because you are holding protein and phosphorus down. With both at once, you cannot load fat for energy, so the carbohydrate and protein balance has to be threaded carefully to keep the dog fueled without overworking the kidneys or the pancreas.
Glucose control versus renal restriction.
Diabetes wants steady, lower-glycemic carbohydrates, consistent timing, and enough protein and fiber to blunt glucose swings. Kidney disease wants moderate protein and low phosphorus. The starchy carbohydrates a renal diet uses for energy can spike a diabetic, so the two goals have to be balanced against each other rather than followed separately.
Crystal risk versus the kidney plan.
Recurring UTIs put hydration and urinary pH front and center, and the right mineral targets depend on the crystal type, struvite or oxalate. A UTI can also raise inflammation and nudge BUN on its own. Managing the urinary picture while still honoring the renal restrictions takes a formulation that weighs both, not a single template.
Limit it, or replace it, depending on the dog.
High potassium means limiting potassium-rich ingredients and sometimes adding binders. But many wholesome foods are potassium-rich, and some kidney dogs run low instead and need more. This is the case a commercial renal diet cannot solve, because it is built for the average dog, not the panel in front of you.
What it would actually take
The study we still need
The honest answer is that the research is not there yet, and a study that could settle it would be large and expensive. My proposed study would have the following:
How it would be built
Five groups of about 120 healthy dogs aged two to six: a kibble control, home-cooked under and over 41% protein, and raw under and over 41% protein. Monthly bloodwork, urinalysis, SDMA, blood pressure, and body condition scoring across a full year. The cost makes it a project for a large manufacturer like Mars or Purina, a vet school such as UC Davis or Tufts paired with a pet insurer, or a consortium of fresh and raw companies working with a research institution. Diverse teams also help guard against bias.
The path forward
Until the research catches up
- Elevated BUN is not a normal consequence of raw or home-cooked feeding. It warrants a look.
- Modern formulation can prevent it when the diet is properly balanced.
- Any elevation should prompt a dietary review with your vet.
- Think beyond the kidneys. A high BUN can be an early flag for inflammation.
- A qualified nutrition professional helps ensure balanced, individual meals.
I have repeatedly seen dogs move from a high BUN to a normal range within three to six months on a properly formulated diet. If you want help building one, that is the work I do. Wishing you and your dogs good health.
Book a call about your dog’s diet →Resources:
Dodds, W. J. (n.d.). Raw diets and bloodwork results: Should you be concerned? Hemopet. https://hemopet.org/raw-diets-and-bloodwork-results-should-you-be-concerned/
Dzanis, D. A. “The Association of American Feed Control Officials Dog and Cat Food Nutrient Profiles: substantiation of nutritional adequacy of complete and balanced pet foods in the United States.” Journal of Nutrition, vol. 124, no. 12 Suppl, Dec. 1994, pp. 2535S-2539S. doi:10.1093/jn/124.suppl_12.2535S.
Head, M. L., et al. “The Extent and Consequences of P-Hacking in Science.” PLoS Biology, vol. 13, no. 3, 13 Mar. 2015, p. e1002106. doi:10.1371/journal.pbio.1002106.
Zabor, E. C., Kaizer, A. M., and B. P. Hobbs. “Randomized Controlled Trials.” Chest, vol. 158, no. 1S, July 2020, pp. S79-S87. doi:10.1016/j.chest.2020.03.013.
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.