Low blood levels of vitamin D are associated with increased risk for everything from heart disease, diabetes and cancer to mood disorders and dementia. So it may not be surprising that vitamin D supplements are popular. However, many people who take vitamin D supplements have no signs of vitamin D deficiency or underlying conditions that would benefit them, and some take doses higher than the safe upper limit.
How much vitamin D do I need?
The current recommended daily allowance (RDA) for vitamin D is 20 micrograms (mcg or mg) or 800 international units (IU) for people over 70 years of age and 15 micrograms (600 IU) for people between 1 and 70 years of age.
The Endocrine Society’s 2024 guidelines state that healthy adults under 75 do not need to take vitamin D supplements. Guidelines only recommend supplements for certain groups, including children (ages 1 to 18), adults over 75, pregnant women, and high-risk prediabetics.
Vitamin D and your health
Vitamin D, also known as the “sunshine vitamin” because it is produced in the body after exposure to sunlight, has long been known to increase the absorption of calcium and phosphorus in the body and help form strong bones. Since the turn of the century, research into the role of vitamin D in various health conditions has rapidly increased.
Although the role of vitamin D in bone health is strongly supported, the evidence that vitamin D prevents other health conditions is still inconclusive.
For example, the Vitamin D and Omega-3 Trial (VITAL), which included more than 25,000 participants aged 50 and older nationwide, found that people taking vitamin D supplements did not have reduced rates of heart attack, stroke, or cancer. However, among people who later developed cancer, those who took vitamin D supplements for at least two years were 25% less likely to die from cancer than those who took a placebo.
Other analyzes of VITAL data found that five years of vitamin D supplementation reduced the risk of being diagnosed with autoimmune diseases such as rheumatoid arthritis and psoriasis by 22%, and four years of vitamin D supplementation was associated with slower rates of cellular aging. However, the VITAL data showed that vitamin D supplements were not effective in preventing depression.
And in 2025, two randomized controlled trials found that vitamin D supplements had no effect on thinking and memory (the VitaMIND trial) or dementia (the Finnish vitamin D trial).
Factors that can affect vitamin D levelsVitamin D levels reflect many factors, including: where you live. People in northern regions (above 37 degrees north latitude) are at higher risk of vitamin D deficiency because their skin receives much less sun exposure during the winter. your age. The skin’s ability to produce vitamin D decreases with age. Over the age of 65, your skin produces only a quarter of the amount of vitamin D that it produced in your 20s. your skin color. People with darker skin usually have lower vitamin D levels than people with lighter skin. On average, African Americans have about half the amount of vitamin D in their blood compared to white Americans. your weight. If your BMI is over 30, your blood levels of vitamin D may be low. Vitamin D is stored in fat, so people with high body fat percentages have less vitamin D in their blood available to their bodies. the food you eat. With the exception of certain fish, few foods naturally contain significant amounts of vitamin D. Most milk is fortified with vitamin D. This is a process introduced by the U.S. government in the 1930s to combat rickets, a bone-weakening disease caused by vitamin D deficiency. Most plant-based milks are also fortified, as are breakfast cereals and some types of orange juice. Certain health conditions. People with conditions such as inflammatory bowel disease, liver disease, and cystic fibrosis have difficulty absorbing vitamin D, which can lead to a deficiency. |
Vitamin D benefits and warnings
High doses of vitamin D can be dangerous. Vitamin D is not soluble in water, so it is not excreted in the urine. Instead, excess vitamin D accumulates in your body’s tissues and bloodstream.
In rare cases, supplements containing too much vitamin D can be toxic. It can cause hypercalcemia, a condition in which too much calcium builds up in the blood and forms deposits in arteries and soft tissues. Taking high doses of vitamin D supplements can make you more likely to develop painful kidney stones.
A study in older adults who were already at risk for falls found that those taking high doses of vitamin D (50 μg to 100 μg, or 2,000 IU to 4,000 IU) had an increased risk of falls compared to lower doses (6.3 μg to 25 μg, or 250 IU to 1,000 IU). A follow-up analysis also suggested that people with the highest blood levels of vitamin D after taking supplements may be at higher risk of falls than those with lower levels.
Ask your doctor whether you should take vitamin D supplements and, if so, in what dosage.
Selected food sources of vitamin D |
||
|
carefully selected ingredients |
microgram (mcg) vitamin D |
FDA Nutrition Facts Label % Daily Value (DV) |
|
cooked salmon, 3 oz. |
11.1 |
55.5% |
|
Tuna, boiled canned, 5 oz. |
1.7 |
8.5% |
|
Sardines, canned oil, 3.75 oz. |
4.4 |
twenty two% |
|
Milk, Low Fat, Fortified, 8 oz. |
2.8 |
14% |
|
Soy milk, unsweetened, fortified, 8 oz. |
1.6 |
8% |
|
Orange Juice, Fortified, 8 oz. |
2.5 |
12.5% |
|
1 large egg yolk |
0.9 |
4.5% |
Source: USDA Food Data Central
Be smart about D
When it comes to vitamin D, it’s best to follow a few simple guidelines.
Pay attention to the numbers. If you’re taking a vitamin D supplement, you probably don’t need more than 15 mcg to 20 mcg (600 IU to 800 IU) per day. Your doctor may recommend a higher dose if you have bone health problems or conditions that interfere with the absorption of vitamin D or calcium. Avoid taking more than 100 mcg (4,000 IU) per day, which is considered a safe upper limit, unless recommended by your medical team.
Choose edibles over pills. If possible, it is better to get vitamin D from food sources rather than supplements (see Selected Food Sources of Vitamin D). Choose foods high in vitamin D, such as fortified dairy products (nutrients added to foods), salmon, and canned fish. Check the product’s nutrition label. The product’s nutrition label includes the amount of vitamin D per serving (mcg) and percent daily value (%DV).
Please inform your doctor. Discuss supplement use with your doctor to ensure the dosage is appropriate for your needs. If you eat a balanced diet that regularly includes a good source of vitamin D, supplements may not be necessary.
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