Vitamin D Supplements (including some rodenticides using the same mechanism)

How Much Is Dangerous

Even over-the-counter vitamin D supplements intended for human use pose a real risk if enough are ingested relative to a cat's small body size; cholecalciferol-based rodenticides specifically are formulated to be highly concentrated, meaning even a small ingested amount of the rodenticide product itself can be genuinely dangerous, more so than an equivalent-looking amount of a typical human supplement bottle might suggest.

Symptoms

• Increased thirst and urination — often the earliest visible sign, appearing before the more serious downstream effects
• Vomiting
• Loss of appetite
• Lethargy and weakness
• Signs of established kidney failure developing over 1–3 days as calcium deposits progressively accumulate in and damage kidney tissue
• Abnormal heart rhythm in advanced cases, reflecting the direct effects of severely elevated blood calcium on cardiac electrical activity

Time to Symptoms

Initial gastrointestinal and thirst-related signs within 12–36 hours of ingestion; kidney injury typically develops over the following several days and, notably, can continue progressing even after the initial exposure has been addressed and treatment has begun, since the calcium deposition process doesn't immediately reverse once started.

First Aid Steps

• Contact a veterinarian or emergency animal hospital promptly for any suspected ingestion of vitamin D supplements or, especially, a cholecalciferol-based rodenticide product specifically
• Bring the product packaging so the exact formulation and concentration can be identified — this significantly affects both treatment urgency and the specific approach taken, since rodenticide-strength cholecalciferol requires more aggressive intervention than a typical human vitamin supplement dose

What Not To Do

• Do not assume vitamin supplements are automatically low-risk simply because they're framed as "just a vitamin" in everyday thinking — vitamin D specifically has a genuinely narrow safety margin and serious toxicity potential that distinguishes it from many other vitamins
• Do not delay seeking care in the hope that mild early signs will resolve on their own — this toxin's effective treatment window closes faster than many other common poisonings on this list, making early action disproportionately valuable here

Veterinary Treatment

Decontamination as early as possible after exposure, since this toxin has a genuinely narrow window before calcium elevation becomes difficult to control through treatment alone. Aggressive IV fluid therapy, medications specifically aimed at lowering blood calcium levels, and close monitoring of kidney values and calcium/phosphorus levels via repeated bloodwork for at least 1–2 weeks after exposure, since effects can be both delayed in onset and prolonged in course. This is considered among the more difficult rodenticide-category toxicities to manage successfully once significant calcium elevation has already occurred, which underscores the value of early, aggressive intervention before that point.

Toxic Compound

Cholecalciferol (vitamin D3), which in excess causes dangerously elevated blood calcium and phosphorus levels, leading to widespread tissue mineralization — the abnormal deposition of calcium in tissues that should not contain it — most seriously and dangerously in the kidneys, where it causes acute kidney failure. This exact mechanism is shared with certain rodenticides specifically formulated around cholecalciferol as their active ingredient, which are notably more dangerous than anticoagulant-type rat poisons (covered separately under Pesticides) because there is a considerably narrower treatment window and no equivalently simple, reliable antidote available.