Vitamin D Pills
As over-the-counter (OTC) supplements have become more popular, more cats and dogs are getting into them. In 2015, the ASPCA Animal Poison Control Center received 28,523 calls regarding over-the-counter supplements compared to 18,260 calls in 2013 — that’s a whopping 56 percent increase. When these incidents occur, pets may be eating a dropped pill or ingesting the contents of the entire bottle. In some cases, pet owners also might be giving these supplements to their pets on purpose to “self-treat” a disorder. Some OTC products are similar to products we give our pets — or, as in the case of vitamin D, may actually be safely prescribed by a veterinarian for your pet when given at proper dosages — but others can be deadly. For that reason, never give your pet any supplement without talking to your veterinarian first. Animal doses can vary greatly when compared to people.


The metabolite of tryptophan called 5-hydroxytryptophan (5-HTP) is one of the most dangerous supplements for pets to get into. The big problem with 5-HTP is that it is absorbed into the central nervous system very rapidly, while tryptophan must be metabolized first and is absorbed more slowly. 5-HTP is used as an alternative supplement to address a variety of disorders in humans including obesity, depression, anxiety, insomnia, premenstrual syndrome (PMS) and compulsive gambling. 5-HTP increases serotonin concentrations in the brain. When there is too much serotonin, serotonin syndrome can develop. Signs of serotonin syndrome in pets include: lethargy, high heart rate, dilated pupils, agitation, vomiting, high body temperature, vocalizing, tremors, seizures and death. Signs can start as early as 15 minutes after ingestion and last 24 to 48 hours. These animals need to see the veterinarian immediately for treatment. Medication can be given to help control seizures and agitation and reduce the amount of serotonin in the brain. The prognosis is generally good if rapid and aggressive care is instituted. 

Vitamin D

While your veterinarian may sometimes prescribe vitamin D for your pet to help with certain disorders, those dosages will be calibrated to be safe. When intended for humans, vitamin D can be found as a single ingredient supplement or in most multivitamins. The amount of vitamin D in these human supplements can vary widely from as little as 100 IU to 5,000 IU, and prescription strength can be up to 50,000 IU. Vitamin D is important for bone strength and reducing inflammation in both pets and humans. Vitamin D overdoses can cause vomiting, calcification of organs and kidney failure, which can lead to increased drinking and urination. The supplement does this by pulling more calcium out of the intestinal tract and bone, and decreasing urinary output of calcium. Gastrointestinal signs are thought to be related to the effects of excess calcium on stomach muscle action and stomach acid secretion.

Vomiting can start within a few hours after ingestion. Animals need to see the veterinarian for treatment as soon as possible. Keep in mind that what might seem like a small dose to you might be a huge dose if the pet is a Chihuahua or of a similar small size. If calcification of organs occurs, it is not reversible. Kidney failure can begin in 24 to 48 hours. Treatment is based on administering fluids and medications to help lower the calcium in the body. Treatment may be prolonged for several weeks. Prognosis is good if caught early.


Iron is another supplement that can be fatal to pets if given at the wrong dosage. Iron can cause vomiting, stomach ulcers and liver failure. It is most commonly found in OTC prenatal or women’s formula vitamins. The amounts will also vary depending on the supplement. Signs in pets usually start one to six hours after ingestion. Simple stomach upset seen at lower doses usually resolves within six to 24 hours. With larger doses, the iron is deposited in the liver and signs may persist days to weeks. If you suspect your pet has ingested this supplement, you should see a veterinarian immediately. There is an antidote that is a specific iron chelator (binder), which helps remove iron from the body. This may be most effective within the first 24 hours. Iron levels can be checked via blood sample to determine if the antidote is needed. Your pet may also need anti-vomiting medications and stomach protectants.

Final Tips

Keep in mind that even some of the supposedly “safer” supplements can be dangerous if they are sweetened with xylitol, which is commonly used in chewable human vitamins and supplements to make them more palatable. Xylitol can cause low blood sugar, liver failure and seizures in dogs.

Please remember to keep all of your OTC products safely away from your pets and be aware that dose determines the level of poisoning. Make sure you have the bottle when you call your veterinarian, as amounts and ingredients can really vary from product to product.

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