Vitamin D Supplements poisoning in dogs and cats
Toxic agent: Cholecalciferol (vitamin D3) · Reviewed 2026-08-18
Phone a vet now, before reading on. Have ready: your pet's weight, roughly how much was eaten and when, and the packaging if there is any. ASPCA Animal Poison Control (+1 888 426 4435), Pet Poison Helpline, or Animal PoisonLine in the UK.
Vitamin D is fat-soluble, so it does not wash out — it builds up. A dropped bottle of high-strength D3 capsules can drive a dog's blood calcium high enough to calcify its kidneys.
What it actually does
Cholecalciferol massively increases calcium absorption from the gut and its release from bone. Blood calcium and phosphorus rise together, and once their product exceeds a threshold, calcium salts precipitate into soft tissue — kidneys, heart, blood vessels and stomach lining. The mineralisation is often permanent, which is what separates this from most poisonings.
How much matters
Human supplement strengths have risen sharply, which has made this worse:
| Toxic from about 0.1 mg/kg | of cholecalciferol |
|---|---|
| A 5000 IU capsule | 0.125 mg — so a 5 kg dog needs only a handful |
| High-strength drops | can carry 4000 IU per drop |
| Also found in | psoriasis creams containing calcipotriene, and cholecalciferol rat baits |
The long half-life is the problem: treatment is measured in weeks of monitoring, not days, because calcium can climb again after it appears controlled.
What you will see, and when
Onset: 12 to 36 hours. Typical course: Two to four weeks of monitoring, sometimes longer.
- 12–24 hoursVomiting, loss of appetite, marked thirst and urination
- 24–72 hoursWeakness, constipation, blood in vomit as the stomach lining mineralises
- 3+ daysKidney failure, irregular heart rhythm, calcification of soft tissue
What the vet will do
Decontamination early, then intravenous fluids with diuresis, and drugs that lower calcium — steroids, then bisphosphonates or calcitonin in serious cases. Calcium and phosphorus are rechecked for weeks because rebound is common.
Outlook
Guarded. Survivable, but soft tissue mineralisation and reduced kidney function are frequently permanent.
Dogs and cats are not the same here
Both, and cats are at least as susceptible. Psoriasis cream licked off a human's skin is a recognised feline exposure.
Where it comes from in a normal house
- High-strength human vitamin D capsules and drops
- Cod liver oil and multivitamins
- Cholecalciferol-based rodenticides
- Calcipotriene psoriasis ointment
- Some fortified pet supplements given on top of a complete diet
The thing people get wrong
“It is a vitamin, so an overdose just passes through.”
That is true of water-soluble vitamins. Vitamin D is fat-soluble and accumulates, and the damage it causes — mineralised kidneys — does not reverse when the level comes down.
PawLife keeps your pet's weight, medication and feeding history in one place, so when you make this call you can answer the vet's questions in seconds. The full food safety database is free.
Get PawLife on the App StoreFrequently asked questions
How much Vitamin D Supplements is dangerous?
The long half-life is the problem: treatment is measured in weeks of monitoring, not days, because calcium can climb again after it appears controlled.
How long after exposure to Vitamin D Supplements do symptoms start?
12 to 36 hours. Vomiting, loss of appetite, marked thirst and urination. Two to four weeks of monitoring, sometimes longer.
Is Vitamin D Supplements worse for cats or dogs?
Both, and cats are at least as susceptible. Psoriasis cream licked off a human's skin is a recognised feline exposure.
Is it true that: It is a vitamin, so an overdose just passes through.
That is true of water-soluble vitamins. Vitamin D is fat-soluble and accumulates, and the damage it causes — mineralised kidneys — does not reverse when the level comes down.
Related emergencies
Sources
This page is information, not veterinary advice. Toxic doses vary with body weight, age, breed and individual sensitivity, and the figures above exist to explain what a vet is assessing, never to decide that an amount is safe. If you are reading this because something has already been eaten, call a vet.