New rabbit reference intervals may refine calcium disorder workups

Version 2 — Full analysis

A newly published study in the American Journal of Veterinary Research gives rabbit clinicians something they haven't had before: reference intervals for intact parathyroid hormone alongside updated intervals for ionized and total calcium in healthy domestic rabbits. In a species where calcium handling is notably different from that of dogs and cats, the paper offers a more defined framework for interpreting lab results tied to calcium balance and parathyroid function. (vetree.app)

The study, published September 3, 2026, was a prospective observational project involving 50 clinically healthy, client-owned adult rabbits between 1 and 7 years old. Samples were collected at a private veterinary hospital over five months, with CBC, serum biochemistry, and point-of-care testing performed, and additional serum testing completed through Michigan State University’s Veterinary Diagnostic Laboratory. According to the study summary, the authors followed American Society for Veterinary Clinical Pathology guidance for reference interval determination. (vetree.app)

The reported intervals were 0.50 to 5.90 pmol/L for intact parathyroid hormone, 12.60 to 16.50 mg/dL for serum total calcium, 1.35 to 1.82 mmol/L for whole-blood ionized calcium measured by i-STAT, and 1.53 to 1.84 mmol/L for serum ionized calcium measured on a benchtop analyzer. The authors also reported a statistically significant difference between whole-blood and serum ionized calcium values, with mean results of 1.64 ± 0.10 mmol/L and 1.70 ± 0.07 mmol/L, respectively, though they considered that difference clinically insignificant. Notably, the study appears to be the first to report a reference interval for intact parathyroid hormone in domestic rabbits using a chemiluminescent assay. (vetree.app)

That matters because rabbit calcium biology has long complicated interpretation. Reviews and reference texts have emphasized that rabbits absorb calcium differently from many other mammals, often maintain comparatively high total serum calcium, and regulate parathyroid hormone at a different ionized calcium set point. Prior literature has also noted that most available reference ranges in pet rabbits have focused on total calcium, even though ionized calcium is the biologically active fraction and may be more informative in some clinical settings. (sciencedirect.com)

Outside commentary specific to this paper was limited at the time of writing, but the broader literature helps explain why the findings are likely to be useful. Published rabbit clinical pathology reviews have repeatedly warned that species differences can make routine mammalian assumptions unreliable, particularly when evaluating hypercalcemia, renal disease, urolithiasis, and bone or dental disorders. Earlier work has also shown that ionized calcium in rabbits may remain in a narrower physiologic range than total calcium, reinforcing the value of having analyte- and sample-specific intervals rather than relying on generalized chemistry panels alone. (pmc.ncbi.nlm.nih.gov)

Why it matters: For veterinary professionals, especially those in exotic, emergency, internal medicine, and clinical pathology settings, this study could sharpen decision-making in rabbit cases where calcium metabolism is part of the differential. A rabbit with suspected renal compromise, nutritional imbalance, soft tissue mineralization, metabolic bone disease, or a possible parathyroid abnormality may now be evaluated against species-specific intervals for intact parathyroid hormone and ionized calcium, not just total calcium. The distinction between whole-blood and serum ionized calcium reference intervals may also help clinicians avoid comparing unlike sample types or platforms. (vetree.app)

There are still practical limits. The population was relatively small, drawn from a single private hospital, and consisted of healthy adult mixed-breed rabbits, so clinicians should be cautious about extending the intervals to juveniles, geriatric rabbits, rabbits with concurrent disease, or potentially breed-specific populations. Even so, in exotic companion mammal medicine, well-characterized reference data can be hard to come by, and this study adds a clinically relevant tool where the evidence base has been thin. That is an inference based on the study design and the gaps described in prior rabbit pathology literature. (vetree.app)

What to watch: Next steps will likely include validation across larger and more diverse rabbit populations, uptake by diagnostic laboratories, and future case-based studies testing how these intervals perform in rabbits with renal disease, dental disease, urolithiasis, and suspected calcium-regulation disorders. (vetree.app)