Should I Take Vitamin D Daily or Weekly?

Medically Reviewed by Felicia Newell, M.S., RDN

December 30, 2023

Vitamin D, often referred to as the "sunshine vitamin," plays a pivotal role in maintaining our health and well-being. It’s crucial for the absorption of calcium in our bodies, promoting bone health and immune function, and it may also have protective effects against certain diseases.

Sun exposure, diet, and supplements are the three ways you can achieve healthy vitamin D levels.

And when it comes to supplementation, a recurring question that I get from my clients is whether they should take their vitamin D daily or weekly. Keep reading to find out.

Should I Take Vitamin D Daily or Weekly?

Vitamin D intake, whether taken daily or weekly, offers unique benefits along with some potential drawbacks…

Daily intake ensures consistent levels in the body, fostering a steady habit.

On the other hand, weekly intake, typically involving higher doses, may be more convenient for those who struggle to remember to take it daily. However, it can lead to short-term spikes in vitamin D levels. Since vitamin D is fat-soluble, you have the flexibility to take higher doses less frequently, unlike water-soluble vitamin supplements.

So what does science say? Studies show that the best results come from taking vitamin D as part of a daily regimen, with dosage at the recommended level (1, 2).

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Age, lifestyle, and geographic location significantly contribute to the choice of dosing frequency. Older adults, who generally have a diminished capacity to synthesize vitamin D, may benefit more from daily intake. Active individuals with ample sun exposure might prefer weekly dosing to supplement their natural vitamin D production. Geography also plays a role as people living in sun-deprived regions might rely more on dietary intake and supplements.

Sun exposure is a great natural source of vitamin D, as the body produces it in response to UVB light. This process is quicker than you may think—just 15 minutes of sunlight on the face, arms, back, or legs (without sunscreen) 3-4 times a week can generate the recommended levels of vitamin D (3). However, this production can change depending on the season, time of day, weather, skin melanin content, and sunscreen

Moreover, overexposure raises the risk of skin damage and cancer, so balancing sunlight exposure and supplementation is important to protect your skin. As always, individual needs vary greatly, so healthcare professionals should guide vitamin D supplementation.

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How Much Vitamin D Should I Take At Once?

The recommended dietary allowances (RDAs) for vitamin D vary based on age, lifestyle, and personal health. For most adults, the RDA is typically around 600 to 800 International Units (IU) or 15-20 micrograms (mcg) per day (4). However, some healthcare professionals may recommend higher doses for individuals who are deficient or at risk of deficiency, often reaching up to 1,000 to 2,000 IU or 25-50 mcg per day. 

NativeNote: It's important to remember that these are general guidelines, and individual needs can vary. So it's best to consult with your doctor or healthcare provider before starting or changing your vitamin D routine.

If you decide to do a weekly dose of vitamin D instead of daily, you will likely be required to take a larger dose. Weekly dosing is a concept that involves taking a medication once a week, rather than daily. This method is mostly for convenience and compliance, as research shows daily doses are more beneficial in terms of results. 

Many individuals find it easier to remember a weekly dose rather than a daily one, reducing the chances of missed doses. Plus, weekly dosing can reduce the burden of taking multiple medications daily, which is especially beneficial for individuals managing several health conditions.

Do Seasonal Changes Affect Dosing?

The frequency of vitamin D dosage can also vary depending on the season and available sunlight. Typically, your body produces vitamin D naturally when exposed to sunlight. However, during the winter months, or if you live in high-latitude regions where sunlight can be minimal, your body may not produce enough of this vital nutrient (5).

In such cases, healthcare providers may recommend a higher dosage or more frequent intake of vitamin D supplements to compensate for the lower sunlight exposure.

During the sunnier months or if you live in abundant sunlight, the need for supplements might be reduced, and a lower dosage may be recommended (5).

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Are There Conditions That Affect Vitamin D Absorption?

Certain medical conditions and lifestyle factors can indeed affect how the body absorbs vitamin D. Conditions such as Crohn's disease, celiac disease, and cystic fibrosis can interfere with the body's ability to absorb fat, which is essential for vitamin D absorption (6).

Additionally, obese individuals may require more vitamin D, as it gets distributed in the fat tissue, reducing its bioavailability.

Certain medications, like steroids or weight loss drugs, can also impact vitamin D absorption.

Age is another factor, with older individuals typically absorbing less vitamin D from sunlight due to changes in the skin. In fact, the production of vitamin D can be reduced by 50% as a result of an age-related decline in renal function (7). 

Lastly, darker skin pigmentation can reduce the skin's ability to produce vitamin D from sunlight. Consequently, individuals with these conditions or factors may need to take higher doses of vitamin D.

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Is There a Difference Between Vitamin D2 & D3?

There is a difference between vitamin D2 and D3, both of which are important for human health. 

Vitamin D2, also known as ergocalciferol, is primarily sourced from plant-based foods and fortified products. On the other hand, vitamin D3, or cholecalciferol, is synthesized by our skin when exposed to sunlight and can also be obtained from certain animal-based foods

While both forms can be used to combat vitamin D deficiency, studies have suggested that vitamin D3 is more effective at raising and maintaining adequate levels of vitamin D in the blood (8). As always, it's crucial to discuss with a healthcare provider to determine the right form and dosage for your specific needs.

How Do I Test My Vitamin D Levels?

To assess your vitamin D levels, a simple blood test known as the 25-hydroxy vitamin D test is typically performed.

This test measures the amount of calcidiol (25(OH)D), the precursor to the active form of vitamin D, in your blood. It is generally considered the most accurate way to assess vitamin D levels. You can arrange this test through your healthcare provider, or in some regions, you can order home testing kits for convenience.

Are There Any Risks When Taking Vitamin D Supplements?

While vitamin D is critical for optimal health, it’s important to note that excessive intake, particularly through supplementation, may increase your risk of vitamin D toxicity or hypervitaminosis D. This condition is generally caused by megadoses of vitamin D supplements—not by diet or sun exposure. 

Symptoms of vitamin D toxicity may include (9): 

  • Nausea
  • Vomiting
  • Weakness
  • Frequent urination 

More serious health risks can include (9):

  • Kidney damage
  • Kidney stones 
  • Heart disease
  • Calcification of soft tissues

Fortunately, to reach that level of toxicity, you would need to take a dosage of around 60,000 IUs—far more than any doctor would recommend.

The frequency of vitamin D dosing can also impact the risk of toxicity. For instance, some studies suggest that daily or weekly dosage regimens are less likely to cause toxicity compared to large, single doses. However, there is still ongoing research in this area.

As vitamin D is fat-soluble and stored in the body for long periods, it's essential to ensure intake is carefully regulated and not excessive. Therefore, it's always advisable to consult with a healthcare professional before starting or changing a vitamin D supplementation routine. They can provide personalized advice based on individual health needs and circumstances.

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Lauren Manaker
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Lauren Manaker

Lauren Manaker is an award-winning registered dietitian (RDN), certified lactation educator (CLE), author, and speaker with over 20 years of experience. She earned her BS in Food Science and Human Nutrition from the University of Florida (go Gators!) and an MS in Clinical Nutrition from Rush University in Chicago.

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    Medical Disclaimer

    This content is for informational and educational purposes only. It is not intended to provide medical advice or to take the place of such advice or treatment from a personal physician. All readers/viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. Neither Dr. Chad Walding nor the publisher of this content takes responsibility for possible health consequences of any person or persons reading or following the information in this educational content. All viewers of this content, especially those taking prescription or over-the-counter medications, should consult their physicians before beginning any nutrition, supplement, or lifestyle program.

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