Who should supplement with vitamin D?

According to the NIH , 1 out of 4 people in the United States have vitamin D levels considered too low to support bone and general health. Some people are at higher risk of vitamin D deficiency, including breastfed infants, older adults, people who do not get enough sun exposure, people with darker skin, people with digestive disorders, those who have had bariatric surgery that reduces the amount of fat absorption in the gut, and people who follow a strict vegan diet. If you fall into any of these categories or you feel you may have symptoms of vitamin D deficiency , talk to your health care practitioner about having bloodwork to test your levels and the possibility of supplementing.

How much vitamin D do I need?

According to the 2020-2025 Dietary Guidelines for Americans , the recommended daily amount of vitamin D is 400 international units (IU) for children up to age 12 months, 600 IU for people ages 1 to 70 years and 800 IU for people over 70 years. However, more important than the amount consumed is the amount of vitamin D in your blood. According to the NIH , levels of 50 nmol/L (20 ng/mL) are adequate for most people to maintain bone health, while levels below 30 nmol/L (12 ng/mL) are too low and could cause your bones to weaken or adversely affect your health.

Who should avoid supplementing with vitamin D?

Any supplement, including vitamin D, has the potential to interact with certain medications and other dietary supplements, according to the FDA . You want to avoid supplementing with vitamin D if you take cholesterol-lowering statins or thiazide diuretics, per the NIH . If you already have high serum levels of vitamin D, calcium or phosphate, or existing kidney problems, you will most likely be advised not to take a supplement as it can increase your risk for toxicity and kidney stones. Get your blood serum level tested first and discuss the results with your health care practitioner before taking any new supplements.

Can I check my vitamin D levels at home?

Yes, you can get a home kit and send your blood sample to the lab. The only way to determine vitamin D deficiency is through a blood serum test where a small blood sample will be collected, such as with a finger-prick test. You then mail your blood sample to a lab to measure vitamin D levels. Beware of "rapid" at-home self-tests, as their validity and reliability have not been proven to be accurate.

Does vitamin D boost your energy levels?

Vitamin D does not directly increase your energy. However, vitamin D plays a vital role in all your cells' functions. To that end, a vitamin D deficiency may result in symptoms like fatigue, musculoskeletal pain or weakness, depression and impaired cognitive function. Fatigue is a commonly reported symptom in people with vitamin D deficiency. Some research, such as a 2023 review in Nutrients , has shown that people with vitamin D deficiency have lessened fatigue after taking vitamin D supplements.

What Happens When You Take Vitamin D Every Day

If you've been spending a lot more time indoors and covered up—either because it's cold outside or you work from home—you may have insufficient levels of vitamin D. Because your body synthesizes vitamin D when exposed to the sun's ultraviolet rays, it's common for people who live in colder regions or who don't spend time outdoors with enough skin exposure to be deficient in this critical nutrient.

Vitamin D is an essential nutrient and hormone associated with healthy bones, muscle function and supporting your immune system, among many other benefits. While it offers an array of impressive benefits, how much vitamin D is really needed? Should you take a vitamin D supplement daily? What happens when you do?

Here we'll discuss what vitamin D is, the types of supplements available, what happens when you take vitamin D supplements daily and how to pick the right one for you.

What Is Vitamin D?

Vitamin D is a fat-soluble vitamin naturally present in some foods, and a hormone produced in the skin in response to sun or UV exposure. According to the National Institutes of Health (NIH), vitamin D promotes calcium absorption in the gut and helps regulate the concentration of calcium and phosphorus in the blood. This, in turn, supports building and maintaining healthy, strong bones and helps regulate skeletal and neuromuscular function.

Aside from supporting your bones, muscles and nerves, vitamin D plays many roles in the rest of the body. More and more research, including a 2020 review in the journal Nutrients, shows that vitamin D reduces inflammation, regulates many cellular processes and metabolism and promotes immunity.

Vitamin D Deficiency

Insufficient amounts of vitamin D can greatly impact your bone health and other functions of your body. Given vitamin D's role in absorbing calcium and building bone, vitamin D deficiency can cause rickets in children and osteomalacia—or "soft bone disease"—in adults, per the National Library of Medicine's resource, StatPearls.

Long-term vitamin D deficiency is associated with reduced immune function and an increased risk of some conditions, such as cardiovascular disease, migraines, depression and certain types of cancer, per a 2021 review published in JAMA Network. Study authors caution, however, that more research is needed to strengthen these associations, as well as how or if supplementation with vitamin D is advantageous.

Vitamin D Supplements

Very few foods naturally contain vitamin D, and most are animal-based. This is why vitamin D supplements are among some of the most popular supplements; it's likely a supplement you should consider. If you shop for vitamin D supplements, you may notice different types, including vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).

Vitamin D2 and D3 differ in chemical structure and sources. Both are absorbed in the small intestine, although some studies suggest that D3 increases vitamin D in serum levels for longer than D2, per a 2021 review published in Nutrients. While there is some debate, currently, the majority of experts believe that D3 is the body's preferred form of vitamin D since the body naturally produces the D3 form when exposed to UV light.

a photo of a woman holding a bottle of supplements — Getty Image

Benefits of Vitamin D

Maintains Your Bone Health

The right amount of vitamin D can support blood serum levels of vitamin D to maintain your bone health. Supplementing with a low daily dose of vitamin D may help reduce your risk of soft or brittle bones, especially for aging adults or adults with digestive or malabsorption problems, but may or may not make a difference in healthy adults. For older adults, taking enough vitamin D combined with calcium can decrease the risk of hip and spine fractures, per a 2023 review published in Nutrients.

Supports Your Immunity

Vitamin D plays an essential role in immunity, as research shows that long-term deficiency can result in adverse health effects. A deficiency in vitamin D decreases the body's ability to fight disease. This, in turn, has been linked to autoimmune diseases like rheumatoid arthritis and inflammatory bowel disease and increased risk of multiple sclerosis, per the 2020 review in Nutrients.

Improves Your Mood

According to a 2020 meta-analysis published in Depression and Anxiety, some studies have suggested that vitamin D may play a critical role in regulating your mood and improving symptoms of depression.

It's worth repeating that your body makes vitamin D when exposed to sunshine. And, getting outdoors in and of itself has been shown to have benefits, including improving mood and cognition, reducing the risk of cardiovascular disease and reducing depression and anxiety, per a 2021 review in the International Journal of Environmental Research and Public Health. So getting outdoors has multiple positive effects, including providing the environment your body needs to produce vitamin D.

Potential Risk of Supplementing with Vitamin D

Many people aren't aware of possible toxicity when it comes to vitamins and minerals—and toxicity from vitamin D is possible. However, vitamin D toxicity most often occurs from supplementation rather than from food or sun exposure.

Taking supplements providing more than 4,000 IU daily of vitamin D is not recommended unless under a health care provider's supervision. According to MedlinePlus, most toxicity occurs with doses above 10,000 IU daily.

Symptoms of vitamin D toxicity mostly include digestive, muscular and neurological ones:

Nausea
Vomiting
Muscle weakness
Loss of appetite
Constipation
Confusion
Disorientation
Involuntary weight loss
Irregular heartbeat
Damage to blood vessels which can damage the heart and kidneys

Additionally, extremely high levels of vitamin D can affect kidney function and result in symptoms such as dehydration, excessive urination and thirst, kidney stones and even kidney failure.

Food Sources

There are very few foods that are naturally rich in vitamin D; however, foods fortified with vitamin D are prevalent in the U.S. food supply. Some food sources include:

Fatty fish like salmon, tuna, herring, swordfish and sardines
Beef liver
Cod liver oil
Egg yolks
Mushrooms
Fortified foods and drinks like dairy products such as cow's milk, cheese and yogurt, soymilk, orange juice and cereals

What to Look for in a Vitamin D Supplement

Amount, Dosage and Delivery

It's important to choose a form of vitamin D that works for you. If your recent blood test indicates that supplementation is needed, your health care practitioner can prescribe the proper amount and form. This is important for optimal absorption if you have a medical condition, like inflammatory bowel disease (Crohn's, celiac disease, ulcerative colitis) or a history of gastric bypass.

"Vitamin D comes in capsule, sublingual (under the tongue) or liquid form. A sublingual may be best for those who have issues absorbing vitamin D," says Gretchen Zimmermann, RD, CDCES, Vice President of Clinical Strategy at Vida Health. "Starting with the form you are most comfortable taking is ideal."

Type of Vitamin D

Research, like the 2022 study published in the Qatar Medical Journal, suggests that D3 is the body's preferred form of vitamin D and may be more effective at raising serum levels. However, you may want to choose based on your lifestyle choices. "Vitamin D2 is produced naturally in some plant and fungi foods, while D3 is produced in animals," says Zimmermann, which may make D2 the more appropriate choice if you follow a vegan diet pattern.

Ingredients List

Take a close look at the ingredients list for filler ingredients, sugar or artificial coloring. "There are ingredients that FDA approves as generally recognized as safe (GRAS), which may be a good basis to ensure that you are not getting harmful additives and preservatives," says Catherine Gervacio, RDN, a registered dietitian nutritionist for Living.Fit.

Reputable Manufacturer and Independent Verification

Since supplements are not regulated by the FDA, choosing a supplement with independent verification can help ensure that the supplement is safe and effective. Some agencies include NSF-certified, ConsumerLab, Labdoor and USP verification. "It's best to get supplements from a reputable manufacturer to ensure quality ingredients," advises Gervacio,

Packaging

Choose a supplement packaged in dark glass or other light-blocking package, which helps protect its efficacy and potency. When you get home, you'll also want to store your vitamins in a cool, dark place if possible.

The Bottom Line

Many people can experience a vitamin D deficiency, especially during winter when there's little sun and people are generally indoors and bundled up. While vitamin D is available in the food supply through some natural and fortified sources, you may still want to take a supplement to ensure your vitamin D levels are sufficient to maintain your bone and general health. If you're thinking of adding a supplement to your diet, speak with your health care practitioner and get your serum levels tested first before choosing a supplement that's right for you.

Frequently Asked Questions

Who should supplement with vitamin D?

According to the NIH, 1 out of 4 people in the United States have vitamin D levels considered too low to support bone and general health. Some people are at higher risk of vitamin D deficiency, including breastfed infants, older adults, people who do not get enough sun exposure, people with darker skin, people with digestive disorders, those who have had bariatric surgery that reduces the amount of fat absorption in the gut, and people who follow a strict vegan diet.

If you fall into any of these categories or you feel you may have symptoms of vitamin D deficiency, talk to your health care practitioner about having bloodwork to test your levels and the possibility of supplementing.
How much vitamin D do I need?

According to the 2020-2025 Dietary Guidelines for Americans, the recommended daily amount of vitamin D is 400 international units (IU) for children up to age 12 months, 600 IU for people ages 1 to 70 years and 800 IU for people over 70 years. However, more important than the amount consumed is the amount of vitamin D in your blood.

According to the NIH, levels of 50 nmol/L (20 ng/mL) are adequate for most people to maintain bone health, while levels below 30 nmol/L (12 ng/mL) are too low and could cause your bones to weaken or adversely affect your health.
Who should avoid supplementing with vitamin D?

Any supplement, including vitamin D, has the potential to interact with certain medications and other dietary supplements, according to the FDA. You want to avoid supplementing with vitamin D if you take cholesterol-lowering statins or thiazide diuretics, per the NIH.

If you already have high serum levels of vitamin D, calcium or phosphate, or existing kidney problems, you will most likely be advised not to take a supplement as it can increase your risk for toxicity and kidney stones. Get your blood serum level tested first and discuss the results with your health care practitioner before taking any new supplements.
Can I check my vitamin D levels at home?

Yes, you can get a home kit and send your blood sample to the lab. The only way to determine vitamin D deficiency is through a blood serum test where a small blood sample will be collected, such as with a finger-prick test. You then mail your blood sample to a lab to measure vitamin D levels.

Beware of "rapid" at-home self-tests, as their validity and reliability have not been proven to be accurate.
Does vitamin D boost your energy levels?

Vitamin D does not directly increase your energy. However, vitamin D plays a vital role in all your cells' functions. To that end, a vitamin D deficiency may result in symptoms like fatigue, musculoskeletal pain or weakness, depression and impaired cognitive function. Fatigue is a commonly reported symptom in people with vitamin D deficiency. Some research, such as a 2023 review in Nutrients, has shown that people with vitamin D deficiency have lessened fatigue after taking vitamin D supplements.