Rhubarb's toxic principle is soluble calcium oxalates, concentrated most heavily in the leaves and roots (the stalk itself is lower-risk). When absorbed from the GI tract, these oxalates bind systemic calcium, which can cause acute hypocalcemia with tremors and tetany, and the resulting calcium oxalate crystals can accumulate in the kidneys and contribute to acute kidney injury.
No specific safe amount is established for cats. Because the leaves and roots carry the highest concentration of oxalates and the resulting effects (hypocalcemia, kidney injury) can be serious, any ingestion of rhubarb leaves or roots warrants contacting a vet.
The leaves and roots contain the highest concentration of the soluble calcium oxalates responsible for toxicity; the stalk carries comparatively lower risk, though rhubarb as a whole is not recommended for cats.
Contact a veterinarian or pet poison hotline right away, noting which part was eaten. The leaves are especially dangerous, so do not wait for symptoms.
General public resources referenced while researching this tool's topic.
General educational guidance based on the references above, not veterinary advice. See our editorial policy for how we choose sources.
This tool is intended for educational purposes only and should not be used as a substitute for emergency veterinary advice, diagnosis, or treatment.
If your pet may have consumed toxic foods, chocolate, medications, chemicals, or other dangerous substances, seek immediate help from a licensed veterinarian or emergency animal service in your area. Do not delay professional care based on calculator or search results alone.
Pet poison hotlines (24/7, US and Canada):
ASPCA Animal Poison Control Center: (888) 426-4435
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Pet Poison Helpline: (855) 764-7661
Pet Poison Helpline states its service covers the U.S., Canada and the Caribbean. The ASPCA line is also used by Canadian pet owners. A consultation fee may apply to both. In Canada, your nearest 24-hour emergency vet clinic is the best first call; elsewhere, use local emergency veterinary directories.
How we calculate results: This tool uses commonly referenced veterinary toxicity thresholds and food safety guidelines. Actual toxicity can vary based on your pet's size, health status, and exact substance consumed. These results are estimates only and do not replace a veterinary assessment.