RDA for Adults
RDA in International Units (IU) and Micrograms (mcg)
Adults age 18 to 70
600 IU (15 mcg)
Adults age 71 and older
800 IU (20 mcg)
Pregnant and lactating people
600 IU (15 mcg)
The recommended dietary allowance for adults per the U.S. Dietary Guidelines for Americans.
Understanding your tolerable upper limit (UL) for vitamin D is crucial for avoiding potential toxicity from too much vitamin D. When evaluating your total vitamin D intake, consider your food intake, sunlight exposure, and any supplements, including multivitamins.
Recommended amount: The amount of vitamin D for healthy adults to take from supplements generally considered safe is up to 1,000 to 2,000 IUs per day.Tolerable upper limit: The UL reflects the maximum daily amount of a vitamin unlikely to cause any adverse health effects. The upper limit for vitamin D for all adults 18 and older is 4,000 IU (100 micrograms).Toxicity: Too much vitamin D is toxic because it affects calcium in the body. Excessive vitamin D intake leads to very high calcium levels, which causes vomiting, muscle weakness, dehydration, and kidney stones, among other symptoms. In severe cases, vitamin D toxicity causes kidney failure, irregular heartbeat, soft tissue calcification, and even death. Vitamin D toxicity is unlikely to result from food sources or sunlight alone. Instead, it occurs from regularly taking high-dose vitamin D supplements.
For further guidance, speak with your healthcare provider, a registered dietitian nutritionist, or pharmacist.
Where to Get Vitamin D
Vitamin D is essential for bone health and immune function. It can be obtained from both food sources and sunlight. While some foods naturally contain vitamin D, others are fortified to help boost your intake. This overview will highlight key natural and fortified sources of vitamin D, as well as the role of supplements and sunlight exposure in maintaining adequate levels.
Again, if you regularly consume any or all of the sources below, including multivitamins, you should check all of your labels to ensure that you do not cumulatively consume too much vitamin D.
Food Sources of Vitamin D
Some foods naturally contain vitamin D, whereas others are fortified. Natural sources of vitamin D include:
Cod liver oil (450 IU per teaspoon or 75% of your daily value, DV)Farmed rainbow trout (645 IU per cooked 3-ounce serving, 108% DV)Mushrooms (0.4 IU per cup of sliced white mushrooms)Sardines (180 IU per 3.75-ounce can serving, 30% DV)Sockeye salmon (570 IU per cooked 3-ounce serving, 95% DV)
Fortified Foods
Fortified foods have vitamin D added to boost the nutrition content. Fortified sources of vitamin D include:
Almond milk (105 IU per 8-ounce serving, 18% DV)Breakfast cereals, 2% cow’s milk (110 IU per 8-ounce serving, 18% DV)Orange juice (105 IU per 8-ounce serving, 18% DV)
Soy milk (110 IU per 8-ounce serving, 19% DV)
Supplements
Based on your current vitamin D levels, you may need a supplement. Vitamin D supplements abound with varying dosages. For adults, they typically range from 400 to 50,000 IUs. Taking over 4,000 IUs a day of vitamin D may not be advisable unless your healthcare provider has suggested you do so.
Vitamin D supplements exist as ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Although there is no consensus on which supplement form is best, some research suggests that vitamin D3 is better at maintaining circulating nutrient levels during the fall and winter. If you live in the northern hemisphere, you may want to consider evaluating your vitamin D levels and possibly supplementing from October through March.
Most multivitamins contain 400 to 600 IU of vitamin D, around the daily amount needed for adults. However, choose a supplement based on your vitamin D blood test results.
Sunlight
Your body produces vitamin D when your skin is exposed to sunlight. Ultraviolet (UV) rays act on prohormone (hormone precursor) vitamin D3 in the skin to trigger a series of reactions that result in the active form of vitamin D. Researchers recommend exposing your face, arms, hands, and legs to sunlight between 10 a.m. and 4 p.m. at least twice weekly for five to 30 minutes to get vitamin D from the sun.
Still, balancing skin damage from the sun with vitamin D production is challenging. Using sunscreen can prevent your body from producing vitamin D. How much vitamin D you get from the sun depends on the time of day you go outside and your use of sunscreen or skin-protecting clothing.
Who Needs a Vitamin D Supplement?
Specific populations are particularly vulnerable to vitamin D deficiency due to factors like age, lifestyle, and health conditions. Understanding these risks can help inform your dietary choices and the need for supplementation to support your overall health.
People with the following should consider their vitamin D intake and, potentially, a supplement:
Limited sun exposure: Vitamin D levels are impacted by clothing, sunscreen use, latitude, and season. People covering their bodies or using high SPF sunscreens absorb less vitamin D from sunlight. In winter, particularly at latitudes above 37 degrees, decreased sunlight and increased clothing lead to lower vitamin D synthesis. Dark skin pigmentation: Melanin, the compound responsible for skin pigmentation, causes individuals with darker skin to absorb less UV light, making vitamin D production from sunlight more challenging. As a result, people with higher melanin in their skin may need to take vitamin D supplements to maintain sufficient levels. Pregnancy: Based on the Dietary Guidelines for Americans, vitamin D needs are not increased during pregnancy. Still, most prenatal supplements contain some vitamin D to ensure a pregnant person gets enough. Depending on your medical history and eating pattern, an additional vitamin D supplement may be beneficial.Autism: Some studies suggest that people with autism may have lower vitamin D levels and would benefit from supplementation. Additionally, some research suggests vitamin D supplementation may help improve hyperactivity in autistic children.At risk of type 1 diabetes: Type 1 diabetes is an autoimmune condition where the pancreas fails to produce insulin. Research suggests that vitamin D may help protect insulin-producing cells. Maintaining adequate vitamin D levels may reduce the risk of developing type 1 diabetes. One study indicated a 9% decrease in risk for every 10 nanomoles per liter (nmol/L) increase in vitamin D up to 113 nmol/L.Type 2 diabetes: Vitamin D supports glucose metabolism, and low levels are linked to an increased risk and progression of type 2 diabetes. Some studies suggest that vitamin D supplementation in people with prediabetes or type 2 diabetes may improve insulin sensitivity and reduce hemoglobin A1c levels (your blood sugar average from the past three months). However, these benefits may only apply when a deficiency is present. Conditions that impact fat or vitamin absorption: Changes to the gastrointestinal tract that affect absorption impact vitamin D levels. People with short bowel disease or inflammatory bowel disease (IBD), such as Crohn’s disease, celiac disease, and, to a lesser extent, ulcerative colitis, tend to have lower circulating vitamin D levels because their intestines are less able to absorb vitamin D.Gastric bypass surgery: Bariatric surgery (weight loss surgery) changes the structure of the gastrointestinal tract. This affects nutrient absorption. Because the body’s ability to absorb fat is decreased, vitamin D deficiency is common following bariatric surgery.Older adults: The body’s ability to produce vitamin D from the sun decreases with age. Additionally, older adults may be less likely to spend significant time outdoors, especially during peak sun hours. The risk of bone loss increases with age. The Bone Health and Osteoporosis Foundation recommends individuals older than 50 take a vitamin D supplement with a higher dose of 800 to 1,000 IU, particularly among people at risk of bone loss.Obesity: Low vitamin D levels can occur among people living with obesity due to multiple factors, including less time outdoors in the sunlight, reduced vitamin D intake, impaired liver production of vitamin D, and increased storage of vitamin D in fat (adipose) cells.
Vegetarian or vegan diet: A vegetarian or vegan diet may provide inadequate vitamin D, especially if it excludes eggs, dairy, and fortified foods. Fortified plant-based milks offer vitamin D, but more than one or two servings daily are needed to meet vitamin D requirements.
Alcohol use disorder (AUD): Vitamin D deficiency is common among people with AUD. Moreover, vitamin D deficiency is a risk factor for liver damage and impaired blood sugar. People with AUD may be less likely to consume enough foods with vitamin D, and alcohol-induced changes in liver function affect vitamin D levels. Specific medications: Some medications interact with vitamin D supplements. Taking vitamin D with statin medications that lower cholesterol may reduce the medication’s effectiveness. Thiazide diuretics decrease the removal of calcium from the body. Vitamin D supplements increase calcium absorption, so taking vitamin D with thiazide diuretics may lead to elevated calcium (hypercalcemia).
Supplement use should be individualized and vetted by a healthcare professional, such as a healthcare provider, pharmacist or registered dietitian. No supplement is intended to treat, cure, or prevent disease.
How to Take Vitamin D Supplements
Although taking vitamin D in the morning may be best for aligning with your body’s circadian rhythm and promoting sleep, the most important thing is regularly taking the supplement. However, pick a time that works best for you and your routine. Aim to take the supplement at the same time daily. This helps establish a routine and ensures consistency with supplementation.
Ways to remember to take vitamin D include the following:
Habit stacking: To remember to take your vitamin D supplement, try habit stacking. Habit stacking involves identifying a current habit and then adding the new behavior (vitamin D supplementation, in this case) to your existing routine. Set reminders: Use alarms or reminders to help you remember to take your vitamin D supplement. Take vitamin D with a meal and fat source: According to one study, vitamin D levels were 32% greater 12 hours after supplementation when taken with a fat-containing meal rather than a fat-free meal. Take your vitamin D with a fat source or fat-containing meal. For example, eat yogurt, cheese, avocado, or nuts or drink a glass of milk with your vitamin D. Breakfast can be a prime time for vitamin D because many common breakfast foods naturally contain fat.
Ultimately, finding a consistent routine for taking your vitamin D supplement, whether in the morning or at a more convenient time for you, is critical to ensuring you reap its benefits for overall health.
Summary
Consider supplementing with vitamin D during the darker months when the sun is less intense. Older adults and individuals with higher melanin concentrations may also consider vitamin D supplementation.
The morning may be the best time to take vitamin D. Taking vitamin D with breakfast limits interactions with melatonin, which can contribute to sleep disturbances. Aim to consume vitamin D with a fat-containing meal to boost absorption.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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