Vitamin D toxicity in dogs is a serious, potentially life-threatening poisoning that’s becoming increasingly common in the UK. Dogs are far more sensitive to excess vitamin D than humans are. Even relatively small amounts can cause dangerously high calcium levels, kidney damage and organ failure. All dogs are vulnerable, but young and inquisitive dogs are most at risk. Talk to a vet without delay if your dog has consumed a vitamin D supplement or rat bait.

Vitamin D toxicity (cholecalciferol or vitamin D3 poisoning) happens when dogs ingest excessive amounts of vitamin D. The most common source is rodenticide (rat bait), which contains high concentrations of vitamin D, but human supplements and multivitamins are also a frequent risk. Even a few human supplement tablets may be toxic, depending on their strength and your dog’s body weight. Excess vitamin D causes dangerously high calcium and phosphorus levels, leading to kidney failure and heart complications. The outcome depends on how much vitamin D your dog consumed and how quickly treatment begins. Severe cases often require intensive hospital care. 

What is vitamin D (cholecalciferol) toxicity in dogs?

Vitamin D toxicity in dogs occurs when they consume excessive quantities of vitamin D3 (cholecalciferol), leading to toxic levels of calcium in their blood. 

• Vitamin D plays an important role in controlling the balance of calcium and another mineral called phosphorus in your dog’s body. 

• Vitamin D may be a popular and beneficial supplement for sun-starved UK humans. But dogs are particularly sensitive to overdose. 

• Excessive intake of Vitamin D overwhelms your dog’s normal calcium regulation.

Effects of Vitamin D on your dog's body include:

• Increased calcium absorption from the gut

• Release of calcium from bones

• Reduced calcium excretion by the kidneys

These actions lead to hypercalcaemia (high blood calcium) and hyperphosphataemia (high blood phosphate), which can damage your dog’s kidneys, heart, gastrointestinal tract and other tissues.

Common causes of vitamin D toxicity in dogs

Dogs can suffer vitamin D toxicity through any of the following:

• Ingesting rodenticides containing cholecalciferol (check labels carefully and retain in case of accidental ingestion)

• Eating human vitamin D supplements or multivitamins

• Ingesting prescription medications containing vitamin D

• Consuming certain psoriasis treatment creams

• Inappropriate dietary supplementation

Vitamin D rodenticides are particularly dangerous because very small quantities can cause severe poisoning, including uncontrolled bleeding and hypercalcaemia.

Symptoms start to develop within 12–36 hours, but kidney damage can occur within 24–72 hours. The sooner treatment begins, the better the outlook for recovery. Talk to a vet without delay. 

Symptoms of vitamin D toxicity in dogs

Signs often develop within 12-48 hours of ingestion. However, some effects may take longer to show up.

• Vomiting, dehydration

• Eating less or nothing at all

• Drinking and urinating (peeing) more 

• Developing lethargy or weakness

• Abdominal pain

• Diarrhoea or becoming constipated

Additional symptoms develop as toxicity progresses:

• Muscle tremors

• Depression or collapse

• Abnormal heart rhythm

• Reduced urine production

• Signs of kidney failure

Severe cases can be life-threatening due to acute kidney injury or cardiac (heart) complications.

Are some dogs more at risk of vitamin D toxicity than others?

All dogs are susceptible to vitamin D toxicity. However, some have a greater risk:

• Young and inquisitive dogs are more likely to chew bait blocks or supplement bottles

• Small breeds: a toxic dose can be reached with smaller quantities

• Dogs living in environments where exposed rodenticides are being used

• Dogs with pre-existing kidney disease are more vulnerable to kidney injury

• Dogs with access to human medications or supplements

• Certain breeds and individuals prone to scavenging and chewing: Labradors, Spaniels

How is vitamin D toxicity diagnosed in dogs?

Vets diagnose vitamin D toxicity based on the history of exposure to the toxin and clinical signs.

Your vet may also:

• Carry out a full physical examination

• Run blood tests to check calcium and phosphorus levels, kidney function (urea, creatinine), electrolytes and general health

• Continue to monitor blood electrolytes: sodium, potassium, chloride, magnesium, calcium, phosphate, and bicarbonates

• Perform urine analysis, including concentration 

• Check blood pressure

• Perform an ECG (electrocardiogram) to check for abnormal heart rhythm 

Early blood testing is essential to provide a baseline, as calcium levels may keep going up for another 24–48 hours.

What’s the treatment for vitamin D toxicity in dogs?

There isn't a specific antidote to reverse vitamin D toxicity. Treatment focuses on lowering calcium levels, protecting the kidneys and preventing further absorption of vitamin D and calcium.

Early treatment significantly improves chances of survival and recovery.

• An injection to empty your dog’s stomach, if ingestion of vitamin D has happened very recently (within the last hour or so). Strictly by a vet and only if safe to do so.

• Administering activated charcoal helps to bind any remaining toxins and minimise absorption from the gut.

• Intravenous fluids (a ‘drip’) to flush kidneys and prevent dehydration.

• Prescription medication to reduce blood calcium (corticosteroids, bisphosphonates), gastric protectants, and anti-nausea medicine.

• Careful ongoing monitoring of kidney values and electrolytes.

• Intensive hospital care for severe cases.

Treatment may continue for several days. Some dogs require prolonged monitoring and support if they develop kidney injury.

How to look after a dog with vitamin D toxicity at home

Vitamin D toxicity cannot be treated safely at home. Always seek prompt help from a vet if you think your dog has been exposed to risk.

Your vet may advise home monitoring after initial treatment:

• Provide your dog with constant access to fresh water

• Give prescribed medications exactly as directed, at the correct time and dose

• Feed your dog a veterinary-recommended diet

• Carefully monitor your dog’s eating, drinking and urination

• Watch for vomiting, lethargy or weakness

• Attend all follow-up blood tests and scheduled check-ups

Never attempt to treat suspected poisoning at home without veterinary advice.

Tips on how to prevent vitamin D toxicity in dogs

• Store rodenticides securely and avoid using them in areas where pets can access.

• If use is unavoidable, opt for covered ‘rat bait stations’ which your dog can’t get into.

• Keep vitamin supplements and medications in secure containers and out of reach.

• Dispose of unused medications safely.

• Check for pet food recalls and only use reputable brands from trusted suppliers. Talk to your vet for advice.

• Remind human guests to secure their bags and belongings as well!

Is my family at risk of catching vitamin D toxicity?

No. Vitamin D toxicity is not contagious. However, safe storage is essential to protect both children and pets.

• Store rodenticides in secure containers

• Keep supplements in child-proof packaging

• Avoid leaving medication on countertops

When you should be worried about vitamin D toxicity in dogs

Seek help from a vet immediately if your dog is:

• Vomiting repeatedly

• Drinking and urinating excessively

• Very lethargic or weak

• Showing muscle tremors

• Collapsed

• Suspected to have eaten rodenticide or high-dose supplements

• Getting worse as time goes on, despite treatment

Joii can help with:

• Assessing the urgency of veterinary treatment

• Monitoring recovery after hospital discharge

• Guidance on safe storage and prevention

Safe treats for dogs