Vitamin D Poisoning in Dogs

What is vitamin D poisoning?

Vitamin D is necessary for the body to absorb calcium, a mineral essential for healthy bones. It is also essential for muscle movement, nervous system function, and immune system function. However, excessive amounts of vitamin D may result in poisoning.

There are two forms of vitamin D: vitamin D2 (ergocalciferol) is produced by plants, fungi, and yeasts, while vitamin D3 (cholecalciferol) is produced by animals.

Poisoning commonly occurs when dogs ingest rodenticides (rat and mouse poisons) that contain vitamin D3 or supplements that contain either form of vitamin D. Vitamin D2 has a much wider margin of safety than vitamin D3 and larger amounts are generally tolerated better by animals.

Many topical psoriasis medications contain potent amounts of vitamin D (calcipotriene, tacalcitol, or calcitriol) and poisoning can occur when pets lick the cream off someone’s skin or directly from the product tube. Improperly formulated pet foods, both commercially produced and homemade, have also resulted in poisoning.

What are the signs of vitamin D poisoning?

Signs of vitamin D poisoning typically start 12 to 36 hours after ingestion. The severity of signs depends upon the amount of vitamin D ingested. Smaller doses may cause signs that include:

• Vomiting
• Diarrhea
• Increased drinking and urination
• Abdominal pain
• Depression
• Lack of appetite

Higher doses can cause elevated levels of calcium and phosphorous in the body, which may result in kidney failure. Severe poisoning may cause signs that include:

• Increased respiratory rate
• Difficulty breathing
• Bleeding in the intestines
• Slow heart rate
• Abnormal heart rhythms
• Mineralization of body tissues

Without appropriate treatment, the animal may die.

How is vitamin D poisoning diagnosed?

Most cases of vitamin D poisoning are diagnosed in dogs that have the expected signs and a known or suspected exposure to vitamin D-containing supplements, rat or mouse poisons, or psoriasis medication. Bloodwork that shows elevated levels of calcium, phosphorous, or markers of kidney damage increases the suspicion of vitamin D poisoning. A urine sample may be tested to help assess kidney function. In some cases, specialized testing may be necessary to rule out other causes of elevated calcium.

How is vitamin D poisoning treated?

As with any poisoning, early treatment allows the best chance for full recovery. If your dog has eaten vitamin D supplements, medications, or rat or mouse poison, contact your veterinarian or Pet Poison Helpline, a 24/7 animal poison center, at 1-800-213-6680 immediately.

The treatment needed depends on the amount ingested and time since ingestion. Early decontamination and treatment decrease the risk of serious poisoning. If a pet ingests vitamin D, diagnostics and treatment include decontamination, blood work monitoring, supportive care, and medication to assist in excretion of calcium or to prevent reabsorption of calcium. If hypercalcemia or kidney injury develops, more aggressive medications and fluid therapy are initiated.  

What care is required after treatment?

Unfortunately, the effects of vitamin D poisoning can last many weeks to months. Bloodwork is typically recommended after the pet is discharged from hospital. If changes to bloodwork occur, monitoring may be required for many weeks. Some dogs may require further hospitalized care, since calcium levels may increase again following initial treatment. Kidney damage may occur in dogs that develop high calcium levels. They may require long-term management for kidney failure.

Pet Poison Helpline, an animal poison center based out of Minneapolis, MN, is available 24/7 for pet owners and veterinary professionals that require assistance treating a potentially poisoned pet. The staff provides treatment advice for poisoning cases of all species, including dogs, cats, birds, small mammals, large animals, and exotic species. As the most cost-effective option for animal poison control care, Pet Poison Helpline’s per-incident fee includes follow-up consultations for the duration of the poison case. Pet Poison Helpline is available in North America by calling 800-213-6680. Additional information can be found online at www.petpoisonhelpline.com.