Vitamin D Poisoning in Dogs
What is vitamin D poisoning?
Vitamin D poisoning occurs when a dog ingests a toxic dose of vitamin D. There are two forms of vitamin D – plant-derived vitamin D2 and animal-derived vitamin D3 (also called cholecalciferol). A common source of vitamin D poisoning is when a dog accidentally ingests rodenticides containing vitamin D. Some examples of these products include Muritan, Mouse-B-Gone, Mouse Killer, Quintox Mouse Seed, Ceva True Grit Rampage, Quintox Rat and Mouse Bait, and Rampage Rat and Mouse Bait. Another source of vitamin D poisoning is the accidental ingestion of certain human medications. Rarer causes of vitamin D poisoning include tainted dog foods, over-supplementation with vitamin D, or poorly balanced diets containing high concentrations of liver, milk, fatty fish, or eggs.
What causes vitamin D poisoning?
Vitamin D is important for maintaining the calcium balance in the body. It does this by enhancing calcium absorption from the gut and kidneys, and in emergency situations it can use calcium from the bones to prevent life-threatening low calcium levels. Calcium is important for normal heart, muscle, and nerve function in addition to bone formation. When a toxic dose of vitamin D is ingested, it causes an abnormal balance of calcium and phosphorus, leading to deadly consequences.
"Vitamin D poisoning causes an imbalance of calcium and phosphorus"
What are the clinical signs of vitamin D poisoning?
Vitamin D poisoning causes a variety of clinical signs. The initial clinical signs, occur anywhere from 8 to 48 hours after ingestion. These initial signs include depression, weakness, and appetite loss. Vomiting, increased drinking and urination, constipation, and dehydration typically follow these signs. In severe and advanced cases, dark, tar-like stools and breathing difficulty may be seen, indicating bleeding in the gut and lungs respectively. Other signs include a slow heart rate, abnormal heart rhythm, and mineralization of the soft tissues around the body.
"Initial signs of poisoning include depression, weakness, and appetite loss."
How is vitamin D poisoning diagnosed?
Vitamin D poisoning is primarily based on a history of vitamin D ingestion and clinical signs consistent to exposure. Laboratory blood tests may confirm suspicions by indicating elevated calcium, phosphorus, and kidney function values. Urine tests will show a lower urine concentration and the presence of calcium. X-rays may show mineralization of soft tissue structures. Tests that confirm your dog has vitamin D poisoning include parathyroid hormone levels, ionized calcium levels, and vitamin D levels, but not all clinics will have access to these tests in house, and blood samples may need to be sent to an outside laboratory.
How is vitamin D poisoning treated?
Vitamin D poisoning treatment will depend on how soon your dog is seen after ingestion. If ingestion is caught within 6 hours, gastrointestinal decontamination will be performed. This includes inducing vomiting and administering activated charcoal. If discovered more than 6 hours after ingestion, calcitonin, prednisone, diuretics, and bisphosphonates may be used to block calcium absorption and increase calcium excretion through the urine.
"Treatment depends on how soon your dog is seen by a veterinarian after ingestion."
Supportive therapy is also needed and includes aggressive fluid administration, dietary restriction of calcium, anti-vomiting medications, and gastrointestinal protectants.
What care will my dog require after treatment?
During and after treatment for Vitamin D poisoning, blood calcium and phosphorus levels must be monitored every 24 to 48 hours for at least a week after exposure, but can be required for several weeks. Supportive care should continue until laboratory values normalize. If your dog makes a full recovery, regular activities can resume. Some dogs may have long-term impairments, such as kidney disease, heart disease, or gastrointestinal disease, and these complications from vitamin-D poisoning will need life-long management.
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