What Happens to Your Body When You Take Vitamin D Supplements Every Day Long Term?

Vitamin D is one of the most commonly used supplements, popular among people who are deficient or think they may have one. But what happens when you take vitamin D tablets daily for a while? Here are three potential benefits – and one risk – to keep in mind.

If you don’t get enough vitamin D through diet or sun exposure, a daily vitamin D supplement may benefit your bones.

When you ingest vitamin D, your kidneys kick in and convert it into calcitriol, the biologically active form of the vitamin. According to Stanford Medicine endocrinologist and internal medicine physician Marilyn Tan, MD, FACE, FACP, calcitriol then promotes calcium absorption through the intestines, which ultimately helps bone growth. Vitamin D also promotes phosphorus absorption, which leads to bone mineral growth, she added.

However, if you do not have a vitamin D deficiency, taking supplemental vitamin D is unlikely to have a significant effect on bone health. A 2022 study found that healthy people taking vitamin D had no fewer fractures than those taking a placebo.

Another advantage of taking vitamin D for those who do not consume enough: better oral health. Your teeth, like your bones, rely on calcium to grow, and vitamin D deficiencies have been linked to poorer oral health.

Wassim Diab, MD, FACP, MHA, an internist and vice chair of the department of medicine at Northwell Health’s Staten Island University Hospital, said vitamin D also helps maintain a healthy balance of minerals in the body, which promotes mineralization of teeth.

Low levels of vitamin D can also throw you out of balance. In addition to weakening bones, deficiencies are associated with “muscle pain and weakness, increasing the risk of falls and fractures,” Diab said.

Research suggests that increasing vitamin D levels can improve balance, strength and gait in people with deficiencies.

Although it is rare, there is such a thing as excess vitamin D. Ingesting excessive amounts can lead to hypercalcemia, a condition in which there is too much calcium in the blood. Symptoms include nausea, vomiting, abdominal pain, cognitive impairment and dehydration.

“Prolonged exposure can lead to serious complications, including kidney failure and potentially dangerous heart rhythm disturbances,” Diab said.

According to Tan, hypercalcemia is riskier for people with chronic kidney disease, which can affect the kidneys’ ability to convert vitamin D into calcitriol, as well as those who have difficulty absorbing the vitamin. To aid absorption, she recommends taking the supplement, which is fat-soluble, with a fatty meal or snack.

However, for most people, especially those who have been diagnosed with a deficiency, vitamin D is a low-risk supplement. “Moderate vitamin D supplementation under the direction of a physician, including monitoring kidney function, calcium levels, and vitamin D blood levels, is generally safe and beneficial,” Diab said.

A simple blood test can tell you if you have a vitamin D deficiency, which is surprisingly common. In the United States, approximately 41% of the population does not get enough essential vitamins.

For most people under the age of 70, the recommended daily intake of vitamin D is 600 IU (15 mcg), which increases to 800 IU (20 mcg) for older adults. It can be difficult to achieve these goals because only a limited number of foods contain or are fortified with vitamin D. Additionally, access to sunlight, which triggers vitamin D production, is not always possible and carries risks.

Although vitamin D deficiencies are usually asymptomatic in adults, they can sometimes lead to fatigue, muscle pain or weakness, bone pain and mood changes, Tan said. If you have symptoms or just want to make sure your vitamin D needs are met, talk to your doctor about getting a test.