--- title: What We Know About Vitamin D Deficiency and Vitamin D Supplements description: Do you have vitamin D deficiency? Should you be tested? Here’s what experts say about vitamin D supplements, based on the latest evidence canonical: https://time.com/3761581/vitamin-d-deficiency/ author: Alice Park article:opinion: false article:content_tier: free article:published_time: 2015-03-27T16:58:26.000Z article:modified_time: 2026-05-11T05:04:49.806Z article:section: Health og:title: Who Should—and Who Shouldn't—Take Vitamin D og:description: Do you have vitamin D deficiency? Should you be tested? Here’s what experts say about vitamin D supplements, based on the latest evidence og:url: https://time.com/3761581/vitamin-d-deficiency/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt960fbf24c09035ec/69878566f887dcda1de8acdb/vitamins.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 2560 og:image:height: 1440 og:image:alt: Vitamins og:type: article twitter:card: summary_large_image twitter:title: Who Should—and Who Shouldn't—Take Vitamin D twitter:description: Do you have vitamin D deficiency? Should you be tested? Here’s what experts say about vitamin D supplements, based on the latest evidence twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt960fbf24c09035ec/69878566f887dcda1de8acdb/vitamins.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Who Should—And Who Shouldn't—Take Vitamin D > Sponsored content. Supplied in partnership with TIME. 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Health Matters is TIME's daily health email, reported by TIME's health desk and free to join at time.com/newsletters. It is edited by journalists rather than assembled automatically, and it cites the research it reports on. #### Is Health Matters free? Yes. Health Matters is a free daily newsletter from TIME, available at time.com/newsletters. #### Who reads TIME's Health Matters newsletter? Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators.  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Mar 27, 2015 4:58 PM UTC  Studio shot of various pills in bottles Studio shot of various pills in bottles Getty Images  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Mar 27, 2015 4:58 PM UTC Does your diet need a little extra D? For researchers, it’s one of nutrition’s most vexing questions. “It’s the wild, wild west,” says Dr. JoAnn Manson, chief of preventive medicine at Brigham and Women’s Hospital and professor of medicine at Harvard Medical School. “The issue has become murkier over time rather than clearer.” Research is mixed about whether doctors should routinely test for vitamin D levels, like they do for cholesterol, and whether people should be supplementing their diets with vitamin D pills. Case in point: a [study just released](http://archinte.jamanetwork.com/article.aspx?articleid=2204033) in _JAMA Internal Medicine_ showed that vitamin D did not lower the risk of falls among an elderly population in Finland. The study, which compared the effects of exercise against vitamin D supplements on falls and resulting injuries, did find, however, that exercise cut the chances of more severe injury from falls in half compared to those who didn’t exercise. **MORE** [Want to Stay Healthy? Don’t Rely on Vitamins](http://healthland.time.com/2013/11/11/want-to-stay-healthy-dont-rely-on-vitamins/?iid=time%5Fspeed) But that doesn’t mean that vitamin D isn’t worth taking at all. The [Institute of Medicine (IOM)](http://time.com/wp-content/uploads/2015/03/vitamin%5Fd%5Fand%5Fcalcium%5F2010%5Freport%5Fbrief.pdf), and the [U.S. Preventive Services Task Force (USPSTF)](http://www.uspreventiveservicestaskforce.org/Page/Topic/recommendation-summary/vitamin-d-deficiency-screening) both recently reviewed all of the evidence on vitamin D and its health effects and concluded that in many cases, D supplementation is beneficial—with some important caveats. The two groups say that 600 international units (IU) are generally enough for most healthy adults and that higher doses of vitamin D don’t necessarily produce more health benefits. They also stress that those benefits are limited to bone health; there isn’t enough evidence to support the idea that taking the vitamin can protect against heart disease, [cancer](http://time.com/16148/vitamin-d-may-double-chances-of-surviving-breast-cancer/), diabetes or [cognitive decline](http://time.com/3089339/study-research-vitamin-d-deficiency-dementia-alzheimers/), all benefits suggested by some smaller studies. “More isn’t necessarily better,” says Manson, who served on the IOM committee. “In some cases, it can be worse.” Overdoing vitamin D can lead to calcium in the urine, which can cause kidney stones. Extremely high doses—around 10,000 IU a day—can trigger calcium deposits in the blood vessels, which can lead to clots that cause heart attacks. The IOM panel recommended no more than 4,000 IU of vitamin D daily to avoid these potential problems. **MORE** [Want to Build Endurance? Cut Back on Vitamin C and E Supplements](http://time.com/3663/want-to-build-endurance-cut-back-on-vitamin-c-and-e-supplements/?iid=time%5Fspeed) When people are tested for vitamin D deficiency and come up short, some researchers caution against treatment. In addition to the dosage risks, there’s also evidence that the lab tests for the type of vitamin D circulating in the blood, 25-hydroxyvitamin D, may not be the most reliable measure of a person’s D levels. Plus, not all labs use the same standard test for picking up 25 hydroxy D, and they set different standards for what are considered normal levels. “Clinicians are often left chasing a number, and trying to get patients’ blood levels up to a certain point,” says Manson. “But when you think about how many people are screened for vitamin D, and the concerns about the reliability in how it’s measured, and the differences in what is considered normal ranges across laboratories, it’s really concerning.” Better data may be coming soon, however. Several large trials are underway in which people are randomly assigned to take different levels of vitamin D supplements so researchers can study their health outcomes, from bone problems to heart disease, cancer, diabetes and more. Manson is overseeing [the largest of these](http://www.vitalstudy.org/), called VITAL, which has 26,000 participants. The results from these studies, which are being conducted in the U.S., Europe, Australia and New Zealand, should be available in 2017\. “We should have conclusive answers in about three years,” Manson says. The studies will also look specifically at whether vitamin D levels and metabolism differ across racial and ethnic groups. Some studies have hinted that disparities by race in heart disease and certain cancer risks may be due to vitamin D, and the randomized trials will hopefully provide more information on whether that’s true. In the meantime, Manson says doctors and patients should follow the IOM and USPSTF guidelines: doctors should not order vitamin D blood tests for all of their patients, and people shouldn’t take more than 600 IU of the vitamin if they are otherwise healthy. The only people who may need regular testing for vitamin D deficiency, and possible supplementation, are those with malabsorption problems like Celiac disease, those who have had bypass surgery, or people who have already had fractures and have been diagnosed with osteoporosis. People taking certain medications, including treatment for tuberculosis, may also need to consider vitamin D pills. For everyone else, however, universal screening isn’t necessary—and there isn’t any reason to take more than the recommended daily allowance of vitamin D. _Read next:_ [_The 4 Most Confusing Things About Sugar_](http://time.com/3746378/confusing-things-sugar/?iid=time%5Freadnext) ### You Asked: Your Top 10 Health Questions Answered  You Asked: Are Cleanses Healthy? Potions that claim to clear your body of toxins might sound alluring, but do they deliver? Illustration by Peter Oumanski for TIME  You Asked: Is Eating Dessert Really That Bad For Me? 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