Vitamin A Poisoning in Dogs

What is vitamin A poisoning?

Vitamin A is an essential vitamin for all species of mammals, birds, and fish. It is necessary for proper growth, vision, reproduction, and skin health. Vitamin A poisoning most commonly occurs when pets are fed raw liver, cod liver oil, or other supplements rich in vitamin A over several weeks to months. 

Poisoning from a single, very large dose of vitamin A, such as a whole bottle of vitamin supplements, is less common but can occur. Cats are more susceptible to vitamin A poisoning than dogs.

Polar bears, seals and walruses accumulate large amounts of vitamin A in their livers, which may result in poisoning if ingested by animals or humans.

What are the clinical signs of vitamin A poisoning?

The signs of vitamin A poisoning can be sudden or delayed in onset. When very large doses of vitamin A are ingested, dogs may quickly develop signs of vomiting, drowsiness, irritability, and peeling of the skin.

More commonly, over-supplementation of vitamin A for weeks to months eventually results in a poor hair coat, rough or dry skin, weakness, weight loss, constipation, excessive bone development, and painful or limited movement. Excessive vitamin A intake during pregnancy has been associated with cleft palate formation and other fetal abnormalities. If you believe your dog has ingested an overdose of vitamin A, immediately call your veterinarian or Pet Poison Helpline, a 24/7 animal poison control center, at 1-800-213-6680.

How is vitamin A poisoning diagnosed?

Most of the time, diagnosis is based on a history of excessive vitamin A supplementation and development of expected clinical signs. X-rays may show excessive bone formation, especially in the neck and chest. Elevated levels of vitamin A in the blood also support the diagnosis. Blood tests to evaluate organ function may also be performed.

How is vitamin A poisoning treated?

If a single, large ingestion of vitamin A occurred within a few hours of treatment, the veterinarian may induce vomiting. Once vomiting is controlled, activated charcoal may be administered, which can decrease absorption of vitamin A by the gastrointestinal tract. Activated charcoal should only be administered by a veterinarian; otherwise, aspiration into the lungs and life-threatening changes in blood sodium levels may occur.

Chronic over-supplementation is typically treated by reducing vitamin A intake through stopping the feeding of raw liver, cod liver oil, or vitamin A supplements. Feeding a commercially prepared, balanced diet or a balanced homemade diet formulated by a veterinary nutritionist is recommended. Once the diet is corrected, blood levels of vitamin A should return to normal within a few weeks. Vitamin A is stored in the liver, and elevated liver values may be present for years.

Excessive bone growth caused by vitamin A poisoning is not reversible, but mobility and comfort may improve once vitamin A levels normalize. In some cases, long-term pain management may be needed.

Pet Poison Helpline, an animal poison control 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.