Vitamin D poisoning, or Cholecalciferol poisoning, in cats occurs due to a calcium overload of the liver and kidneys. Vitamin D is quickly absorbed by the body and stored in the adipose (fat) tissue shortly after ingestion. A healthy amount of vitamin D is converted to calcifediol by the liver to be metabolized by the kidneys and distributed in the blood plasma. Just the right amount of vitamin D will aid the body’s control of the nervous system, muscles and aid in the formation of bone, as the organs regulate a proper balance of phosphorus, plus calcium. However, when large amounts of vitamin D are absorbed, the body produces too much phosphorous and calcium (hyperphosphatemia and hypercalcemia), resulting in kidney failure as well as cardiac abnormalities.

Vitamins and minerals are needed to maintain bodily functions in your cat, but an overdose of these essential elements can have ill effects. Vitamin D poisoning in cats occurs when your cat has ingested more vitamin D than the body can handle, causing a lethal overdose. Vitamin supplements, rat poison, and even some plants contain high levels of the D vitamin known as cholecalciferol. When a feline ingests high levels of cholecalciferol accidently, or if the owner overdoses the cat with vitamin D, the body is overwhelmed and the once helpful vitamin becomes a poison.

Vitamin D poisoning in cats caused by ingestion of a pesticide, a supplement overdose, or accidental consumption, will cause the feline’s calcium levels to drastically increase. This high level of calcium, also known as hypercalcemia, can cause a mineralization (hardening) of the lungs, stomach wall, kidneys, and blood vessels. Once the high levels of calcium have caused mineralization to occur throughout the body, the feline will undergo kidney failure, complications of the heart, and internal bleeding. 

Clinical signs of vitamin D poisoning in cats will generally develop between 18 and 36 hours after ingestion. Initial symptoms of vitamin D poisoning in cats include:

As the body reacts to the high level of vitamin D, the cat’s calcium and phosphorus serum levels rise within 12 to 24 hours after ingestion, causing secondary symptoms of: 

Vitamin D poisoning in cats is caused by accidental consumption of a vitamin D containing product or overdose of a vitamin D products, plant, or supplement. Common vitamin D containing products that cats can come in contact with and have poison potential include: 

Diagnosis of vitamin D poisoning in cats is primarily established through a physical examination and the signs the cat is presenting. The veterinarian will ask you what types of plants, pesticides, and household medications your cat could have easy access to on a daily basis. He or she will also ask you what type of medications and supplements your cat is currently taking, as he reviews your cat’s medical history. Diagnostic testing will most likely begin with a urinalysis, biochemistry profile, and complete blood count. Vitamin D toxicity will cause your cat’s phosphate and calcium levels to rise drastically. Therefore, diagnostic tests of the urine and blood will help your veterinarian in diagnosing the problem at hand. Vitamin D poisoning also causes internal bleeding as your cat’s clotting factors deplete, therefore, an anticoagulation test is also a common diagnostic test performed. 

Vitamin D poisoning in cats is an emergency situation and your veterinarian will want to begin treatment as soon as possible. Your veterinarian may try to induce vomiting in an attempted to remove an ingested substance before it is absorbed. If the poison has already been absorbed by the body, the doctor may try an activated charcoal which will bind to the toxin, preventing further absorption. Intravenous fluid therapy is commonly given to the cat to aid in eliminating the poison through urination and a blood transfusion may be necessary to those who have lost blood due to internal bleeding. All vitamin D poisoned felines will be hospitalized during treatment. 

Unfortunately, the prognosis for vitamin D poisoning in cats is rather poor, even with treatment if symptoms have become present. They key to a cat surviving vitamin D poisoning is timing. If a pet owner is present to see the feline ingest an excessive amount of vitamin D or if you realize you have overdosed your cat with a vitamin D supplement, rush your cat to the emergency veterinary center immediately.