Are Human Vitamins and Supplements Dangerous for Pets?

By John Gilpatrick

Dog and cat owners are always thinking about their pets’ nutrition. That’s because a diet packed with the appropriate amount of essential vitamins and minerals is one of the best and easiest ways to both prevent and combat many medical problems.

So, you might think, what’s the harm in giving my pet one of my multivitamins? If a vitamin is good enough for a human, it should be good enough for a dog or cat, right?

Not necessarily.

The variation of dietary needs for humans and pets is one reason, and the way each vitamin product is formulated depending on the manufacturer is another.

According to Dr. Susan G. Wynn, a nutrition specialist at BluePearl Georgia Veterinary Specialists and a diplomate of the American College of Veterinary Nutrition, most commercial pet foods provide dogs and cats with the nutritional balance they need, rendering supplements unnecessary.

Because of this, she says, “most pet multivitamins are designed to contain just a portion of the daily requirement for that species, typically about 20 percent, whereas human supplements can contain 100 percent of the daily requirement.”

This means that consuming a human-grade vitamin can potentially give your pet an unhealthy excess of a particular vitamin or mineral.

What to Do If Your Pet Accidentally Consumes a Human Vitamin

For many pets, sneaking behind your back and consuming one of your vitamins that you left sitting on the table is not cause for an emergency. However, you should still take the situation seriously, says Dr. Lisa Murphy, associate professor of toxicology at the University of Pennsylvania School of Veterinary Medicine and director of the Pennsylvania Animal Diagnostic Laboratory System.

“Animals will react differently depending on their age, medical history, and weight, among many other factors,” Murphy says. But, she adds, “no matter the factors, the likelihood of a positive outcome is so much greater with a prompt phone call to the vet.”

Vitamins That Are Toxic to Pets

Murphy says one of the most serious situations involves prenatal vitamins, which are high in iron and can cause iron toxicity in pets. If your dog or cat happens to knock over a bottle of prenatal vitamins and swallows a bunch before you can intervene, you need to call your vet immediately.

Similarly, vitamin D supplements are fairly serious because too much vitamin D can increase levels of calcium and phosphorus, which can eventually lead to permanent problems with the heart and kidneys, among other organs, Murphy says.

Many other vitamins and supplements—like fiber supplements and many multivitamins—are less serious, Murphy says, but if consumed in large enough amounts, any human-grade vitamin may represent a threat to a pet’s health.

Whenever you see your pet ingest a vitamin or other human supplement, make sure to keep the vitamin bottle on hand in case you have to visit your vet or an emergency animal hospital. The doctor will be able to treat your pet more efficiently with information about dosage and ingredients.

What Are Some Symptoms of Illness Related to Human Vitamins?

This is all good when you witness the incident, but what happens if your pet eats a vitamin without your knowledge?

Murphy says many of the symptoms at play are the same for when a dog or cat eats anything out of the ordinary: vomiting, drooling, lack of appetite, and obvious abdominal discomfort. You may see these symptoms persist for 12 to 24 hours. Whether you are certain or not that your pet has ingested a supplement, if these symptoms continue past that point, it’s time to seek some additional medical help, Murphy says.

Do Pets Ever Need Additional Vitamins and Supplements?

“Healthy dogs and cats eating complete and balanced diets do not need extra vitamins and minerals,” Wynn says.

Murphy adds that nutritional content in most commercial pet foods on the market is governed by the Association of American Feed Control Officials (AAFCO). Anything that meets AAFCO’s requirements shouldn’t cause vitamin or mineral deficiencies. “It’s like fortified kid’s cereal, but even better because it’s formulated for a total diet,” she says.

One exception can occur in cases where an animal has a very low metabolism and requires dramatic food reduction in order to prevent weight gain. “If the owner ends up reducing the calories in a balanced diet too much, the other nutrients will be reduced as well, potentially creating nutritional deficiencies,” Wynn says.

Therefore, a pet-grade multivitamin or mineral supplement can help make up the difference. Consult with your veterinarian or a veterinary nutritionist to help you determine if your pet needs dietary supplements.