Here’s Why Too Much Vitamin D Can Cause Major Health Problems

A man's recent overdose on vitamin D landed him in the hospital for three months. Here's how much vitamin D you really need, according to health authorities.

At this point, it’s pretty commonly known that one significant source of vitamin D is the sun. To be specific, researchers suggest getting between five and 30 minutes of direct sunlight absorbed in the skin at least twice a week. While there are some dietary sources of vitamin D you can rely on—like salmon, eggs, some mushrooms, and fortified dairy products—the sun tends to be a powerful and widely accessible resource for vitamin D exposure.

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For dietary sources of vitamin D, the Recommended Dietary Allowance (RDA) for vitamin D according to the National Institutes of Health is 600 international units (IU) for adults up to 70, and 800 IU for adults over 70. If an adult isn’t getting a sufficient amount of vitamin D—especially during colder months when it’s difficult to be outside, or there’s less sunlight available in the day for sun exposure—their doctor may recommend they should take a vitamin D supplement.

Getting sufficient vitamin D is vital, especially for adults over the age of 70. Vitamin D is connected to calcium intake, which helps with building bone tissue. Given that bone density starts to break down after the age of 50, choosing calcium-rich foods and getting sufficient vitamin D (which converts to calcium in the liver) is vital for strengthening aging bones and preventing bone health issues.

However, taking too much vitamin D can have negative ramifications on your health.

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Signs of vitamin D toxicity

Recently a middle-aged man was hospitalized for three months after experiencing vomiting, nausea, abdominal pain, leg cramps, tinnitus, dry mouth, increased thirst, diarrhea, and a 28-pound weight loss. The result was due to an overdose of vitamin D supplements. The patient was taking 150,000 IU instead of the daily requirement, according to Medical News Today.

For most individuals ages nine years and up, the tolerable upper intake limit (UL) for vitamin D is 4,000 IU. A quick browse at your local pharmacy will show you that most vitamin D supplements on shelves offer a range—anywhere between the RDA and the UL. Some supplements even go above the UL, offering 5,000 IU per dose. (These products are often produced for some older individuals, or people with illnesses whose digestive systems don’t appropriately absorb the vitamins and minerals the body needs.)

While vitamin D toxicity is rare, it can happen if the body is exposed to too much through supplementation. Vitamin D toxicity cannot happen through sun exposure because the body works to regulate the production of it, and consuming vitamin D through food is relatively rare already. Supplements are most likely the cause of any vitamin D toxicity an individual would experience.

Long-term vitamin D toxicity causes elevated levels of calcium in the blood. High levels of calcium can lead to tissue and blood vessel damage, as well as some of the severe symptoms explained—nausea, weakness, vomiting, and frequent urination.

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How to choose the right vitamin D supplement

The first step in choosing the best vitamin D supplement for you is to talk to a doctor. Find out what a good level of supplementation would be for your body—and whether you need to take it year-round, or just during the months when your skin isn’t getting as much sun exposure.

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Again, while it is rare to experience vitamin d toxicity, it is important to not overdo it on how much you are taking over time. Remember, 800 IU may be a reliable amount for your daily needs, and you only need to stand in the sun for a few minutes each week to get a sufficient amount for your health. The 5 Best Hormone-Safe Sunscreens, Recommended by Doctors

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Kiersten Hickman
Kiersten Hickman is a journalist and content strategist with a main focus on nutrition, health, and wellness coverage. She holds an MA in Journalism from DePaul University and a Nutrition Science certificate from Stanford Medicine. Her work has been featured in publications including Taste of Home, Reader's Digest, Bustle, Buzzfeed, INSIDER, MSN, Eat This, Not That!, and more.