Vitamin D is an essential nutrient for most animals, including humans and dogs. While humans and certain animals are able to synthesize Vitamin D from the sun via their skin, dogs mainly get Vitamin D from their diets. Although dogs need Vitamin D to survive and thrive, too much Vitamin D can be toxic to dogs.

Dogs and Vitamin D

Dogs need a certain amount of Vitamin D in their diets to maintain a healthy balance of calcium and phosphorus in their bodies. This helps keep their bones healthy and plays an important role in the functions of muscles, nerves and all cells in the body.

There are two predominant types of Vitamin D. Ergocalciferol (D₂) is derived from plants. Cholecalciferol (D₃) is derived from animal sources. Dogs are not able to synthesize a significant amount of Vitamin D from the sun the way humans and some other animals can and therefore must get it from their diets. Dogs in the wild likely get most of their Vitamin D from eating animal fat. Some may come from eating plants.

Most commercial dog foods are supplemented with Vitamin D, but their levels can vary. Additional supplementation of Vitamin D is not usually needed. Ask your veterinarian for advice about Vitamin D and your dog. If needed, your vet can check your dog's levels and help you make any necessary adjustments.

Causes of Vitamin D Poisoning in Dogs

Dogs store Vitamin D in their fat and liver. Because it is not water-soluble, they are unable to excrete excess amounts in their urine.

It can take as little as a dose of 0.1 mg/kg to cause vitamin D poisoning. That's about 0.45 mg per 10 pounds of body weight. The fatal dose is around 2 mg/kg, which equals about 9 mg in a 10-pound dog.

There are three main ways dogs can ingest dangerous amounts of Vitamin D.

Dog Food With Too Much Vitamin D

Some experts used to think that commercial dog food did not contain enough Vitamin D. However, several brands of dog food had voluntary recalls when it was found that their diets contained an excessive amount of Vitamin D. Fortunately, most reputable commercial dog food companies test their food for proper levels.

Getting Into Vitamin D Supplements

Some dogs like to get into anything and everything they can find. When a dog finds Vitamin D supplements, they are usually human supplements that the owner accidentally left within reach. If your dog gets into your medications and eats your Vitamin D supplements, he can easily get enough to cause toxicosis.

Ingesting Rat Poison With Cholecalciferol

There are several types of rodenticides out there, all of which can harm dogs. Because rat poison tastes good to dogs, it is relatively common for dogs to find it and eat it.

Symptoms of Vitamin D Poisoning in Dogs

The signs of Vitamin D toxicity typically appear within about 12-36 hours of ingestion. Signs may be subtle at first and progress to severe.

Left untreated, Vitamin D poisoning can lead to kidney failure and even death.

Treatment of Vitamin D Poisoning in Dogs

If you suspect your dog has consumed too much Vitamin D, get your dog to a veterinarian as soon as possible. Bring any packaging you have for your dog's diet, your own Vitamin D supplements, and any rodenticide you use.

Your vet will begin by getting a detailed history from you and then examining your dog. If Vitamin D ingestion happened recently, you vet may decide to induce vomiting, then administer activated charcoal to absorb Vitamin D from the GI tract.

Lab tests will be needed to look at your dog's organ function and cell counts. Your vet will likely want to look closely at the calcium, phosphorus, and Vitamin D levels in the blood. The kidney values and electrolytes will also be monitored.

Treatment involves hospitalization with intravenous fluids to support and assist the kidneys. Blood levels will be monitored regularly during hospitalization. The vet may also administer a diuretic to encourage the kidneys to excrete excess calcium. A gastrointestinal protectant is also commonly used, such as furosemide. In some cases, an oral steroid will be given to minimize the absorption of calcium in the GI tract and bones.

How to Prevent Vitamin D Poisoning in Dogs

It's important to keep your dog safe from accidental Vitamin D poisoning. If you have Vitamin D supplements, make sure they stay in a location that your dog cannot access. Avoid using rodenticides of any kind in and around your home. Choose a dog food that contains appropriate Vitamin D levels. Fortunately, manufacturers tend to rapidly recall any diets they find to have too much Vitamin D. Stay up to date on dog food recalls so you can avoid feeding your dog one that is unsafe.