Are you taking too much vitamin D? How to find the right supplement dosage for you

• Yes, you can take too much vitamin D, which causes vitamin D toxicity.
• Signs you had too much vitamin D include vomiting, weakness, and nausea.
• To treat vitamin D toxicity, stop taking vitamin D supplements or consuming vitamin d-rich foods.

Vitamin D toxicity, also known as hypervitaminosis D, is a rare condition that occurs when a person has consumed too much vitamin D.

Vitamin D is a nutrient that helps the body absorb and regulate calcium in the blood. So when a person has too much, it can lead to dangerously high levels of blood calcium, a condition called hypercalcemia.

Vitamin D toxicity is rare and may often go unrecognized, according to Catharine Ross, a professor of nutrition and physiology and head of Nutritional Sciences at Pennsylvania State University. Here's how to spot vitamin D toxicity and what to do about it.

Symptoms and diagnosis

Symptoms of vitamin D toxicity are directly related to excess calcium in the blood, which can cause nausea, vomiting, loss of appetite, frequent urination, weakness, and bone pain.

Over time, the extra calcium can form deposits in the arteries and soft tissue instead of in the bones. Ultimately, this can cause kidney stones and may contribute to heart damage.

"This is the major impact of acute vitamin D toxicity, and it may be occurring slowly in people taking high vitamin D for years," says Paul Price, Distinguished Professor Emeritus of Molecular Biology at University of California San Diego.

To diagnose vitamin D toxicity, a physician will administer a blood test that will show how much calcium is in the blood. If a person has vitamin D toxicity, then calcium levels will be abnormally high.

Ross notes that taking consistently high levels of vitamin D over long periods of time may not cause apparent toxicity in the short term, but may contribute to a higher risk of common symptoms further down the line.

Treatment

If a person shows signs of vitamin D toxicity, the first step toward treating it is to immediately stop taking any and all vitamin D and calcium supplements, as well as reducing intake of foods rich in vitamin D like salmon and cod liver oil.

Doctors may also administer medications to help the body metabolize less vitamin D and pass more calcium.

You may also be prescribed bone resorption inhibitors. These medications are usually used to treat osteoporosis because they prevent the release of calcium into the bloodstream. However, Price's research has shown that bone resorption inhibitors may also prevent acute episodes of vitamin D toxicity.

These inhibitors, he says, could be useful to prevent calcification of soft tissue in patients who, for health reasons, can't reduce their intake of vitamin D.

For most people, though, the answer will be to simply stop your supplements, which will allow your body to process the excess calcium and, over weeks or months, return to normal.

Daily recommended value

Vitamin D is a nutrient that helps your body absorb and regulate calcium. Therefore, it plays an essential role in helping you grow and maintain bone tissue throughout life.

Our bodies get vitamin D in two ways: through sun exposure and from certain foods. How much you need depends on your age, according to the National Institutes of Health. For example, adults require less than people over 70, who produce less vitamin D through their skin.

The National Institutes of Health recommend that most adults need 600 international units (IU) each day to cover their basic needs for bone health. However, for overall health, it's best to get somewhere between 600 IU to 4,000 IU per day.

Fish is a great way to cover your bases, while vegans and vegetarians can look to almond milk and mushrooms. Three ounces of fatty fish, like salmon, or a cup of portobello mushrooms will take care of your daily vitamin D needs.

Ross says that if you occasionally consume the maximum recommended amount - 4,000 IU - it won't hurt you. But if you are consistently reaching or exceeding this limit for months or years on-end, that's when it may lead to symptoms of toxicity.

Causes

Ross says that the vitamin D your skin produces through sun exposure is hard to quantify but in general, it's supplements - not sunlight - that tips the scales towards toxicity.

If you get a severe sunburn, for example, you should be more concerned about skin damage than vitamin D toxicity. Moreover, vitamin D deficiency is more of a concern than toxicity.

This is especially true for children, who can develop rickets if they're vitamin D-deficient, leading to soft and poorly developed bones. The American Academy of Pediatrics recommends supplements for infants who are breast-feeding, or not getting sufficient vitamin D through formula.

Ultimately, based on your age, your lifestyle, and other factors, your doctor will tell you whether you should consider a supplement.

Vitamin D supplementation on the rise

Between 2006 and 2014, the number of people taking over 4,000 IUs daily rose from less than 0.5% to over 3%. That was according to a 2017 study in the Journal of American Medicine, which pulled data from 39,000 participants in the National Health and Nutrition Examination Survey.

The study also found that over the same period, those taking more than 1,000 IUs per day jumped from less than 1% to over 18%. This amount is not known to cause immediate health problems, but the findings indicate that more people than ever are seeking out extra vitamin D and may be at risk of overdoing it.

This doesn't mean that no one should take a vitamin D supplement. Other than infants and those over 70 who likely require supplements, people should get their blood levels checked routinely to determine if supplements are advised.

Insider's takeaway

If you decide you're interested in taking a vitamin D supplement, read the label, buy from a reputable brand, and check to make sure that the product has been third-party tested for safety and potency. Supplements are only loosely regulated by the Food and Drug Administration.

"There are purified vitamin D3 supplements on the market at 10,000 IU per capsule," Ross says, "so some manufacturers are, knowingly, not playing safe with the public." Again, it is inadvisable to take more than 4,000 IU per day for long periods of time.

She adds that the few studies done on intake levels this high were short-term, lasting less than a year, so the result of taking 10,000 IU over a long time is unknown. But, as with many things in life, consuming anything to excess is probably not a great idea for your long-term health.

Vitamin D research has received a lot of attention in recent years, and many potential benefits are emerging. Supplements are not necessarily off the table but don't go in thinking more is better - unless you love kidney stones.