QUICK SUMMARY
What causes vitamin D deficiency? Low vitamin D can result from limited UVB exposure, low dietary intake, darker skin pigmentation, older age, fat-malabsorption disorders, obesity, bariatric surgery, certain medications, and liver or kidney conditions that interfere with vitamin D metabolism.
Vitamin D is essential for calcium absorption, bone mineralization, normal muscle and nerve function, and immune regulation. Many people with low vitamin D have no obvious symptoms. More significant or prolonged deficiency can contribute to bone pain, muscle weakness, osteomalacia in adults, and rickets in children. Fatigue and low mood may occur alongside low vitamin D, but they are nonspecific and should not be used to diagnose deficiency by themselves.
The best natural strategy is balanced: spend regular time outdoors, avoid sunburn, eat vitamin D-rich foods, test 25-hydroxyvitamin D when there is a clinical reason, and use vitamin D3 supplementation when sunlight and food are not enough. We often prefer D3 with K2 as part of a whole-food, mineral-rich bone-health strategy, while recognizing that K2 is not required for every person taking vitamin D.
Vitamin D is not just another nutrient.
It is a sunshine-connected, hormone-like vitamin that touches calcium metabolism, bones, muscles, immune function, and many cellular processes throughout the body.
And in a world where many of us spend most of our lives indoors, low vitamin D is not surprising.
But the answer is not fear, megadosing, or reckless sun exposure.
The answer is wisdom.
Get outside regularly. Avoid burning. Eat nutrient-rich foods. Test when there is a reason. Supplement when appropriate. Support your bones with movement, minerals, protein, and strength training.
And remember, God made light before He made living creatures.
Your body was designed to live in rhythm with His creation.
A few intentional habits can help restore that rhythm and support the abundant life He calls you to live.
Table of Contents
How Much Sun Do You Really Need?
Vitamin D inadequacy remains common, especially in people with limited UVB exposure, darker skin, older age, obesity, malabsorption, or other risk factors. But there is no trustworthy one-size-fits-all number of minutes in the sun that guarantees a certain vitamin D level.
Your skin can make vitamin D when UVB radiation reaches it, but production varies dramatically with:
- Skin pigmentation
- Latitude
- Season
- Time of day
- Cloud cover and air pollution
- Age
- Clothing and how much skin is exposed
- Individual biology
The NIH notes that these factors make it difficult to give a universal sun-exposure recommendation for vitamin D. (1)
That is why I would not turn “10 minutes” or “30 minutes” into a rule.
Our Natural Living Family approach is simple: get regular outdoor light, use wisdom with your skin, and never chase vitamin D by burning yourself.
Finding the Right Balance
Sunlight is part of God's natural design, and time outdoors gives us benefits that go beyond vitamin D. At the same time, ultraviolet radiation can damage skin and increase skin-cancer risk. The American Academy of Dermatology states that there is no defined UV exposure level that maximizes vitamin D synthesis without increasing skin-cancer risk. (3)
That does not mean you need to fear the sun or live indoors.
It means you should not use a universal unprotected-sun prescription as though more UV is always better.
Spend time outdoors. Avoid burning. Use shade, clothing, and sun protection when exposure will be prolonged or intense. If your lifestyle, season, skin tone, or health makes vitamin D production unreliable, food and supplements can fill the gap.
Sunscreen deserves nuance, too. Sunscreen can reduce UVB reaching the skin under controlled conditions, but NIH notes that people typically do not apply enough, cover every exposed area, or reapply perfectly, so some vitamin D synthesis probably still occurs during ordinary use. (1) Sunscreen use should not automatically be blamed for vitamin D deficiency.
Morning Light Is Still Valuable
Early outdoor light is wonderful for your daily rhythm even when the UVB intensity is too low to make much vitamin D.
Morning light helps anchor the body's circadian clock and creates a clear day-night signal. That can support the rhythms involved in alertness during the day and sleep at night.
This is one reason we love getting outside early in the day.
God designed our bodies to live in rhythm with light and darkness, activity and rest, work and worship.
The Bottom Line
There is no universal vitamin D sun timer.
Aim for regular outdoor time without burning, remember that winter and northern latitudes can make UVB unreliable, and use food, supplementation, or testing when the situation calls for it.
The goal is wisdom, not fear of sunshine and not reckless exposure.
Common Causes of Vitamin D Deficiency
Vitamin D deficiency is usually not caused by one thing. Sun exposure, diet, absorption, body composition, age, medications, and organ function can all change the picture.
Vitamin D status is typically evaluated with a blood test called 25-hydroxyvitamin D, written as 25(OH)D. The NIH Food and Nutrition Board considers levels below 30 nmol/L, or 12 ng/mL, associated with vitamin D deficiency and levels of 50 nmol/L, or 20 ng/mL, or higher adequate for most healthy people for bone and overall health. Levels above 125 nmol/L, or 50 ng/mL, may be associated with adverse effects. (1)
One important update: the 2024 Endocrine Society guideline no longer endorses universal “sufficiency” or “insufficiency” target ranges for disease prevention and advises against routine 25(OH)D screening in generally healthy adults without another indication. (2) That means testing should be purposeful, not automatic.
Common causes and risk factors include:
- Limited UVB exposure: Indoor lifestyles, extensive covering of the skin, winter, latitude, and other factors can reduce cutaneous vitamin D production.
- Low dietary intake: Few foods naturally contain substantial vitamin D. Fatty fish are among the richest natural sources, while egg yolks and liver provide smaller amounts. See our guide to grass-fed animal foods.
- Darker skin pigmentation: Melanin reduces vitamin D production from a given UVB exposure. This can contribute to lower average 25(OH)D concentrations, especially when sunlight is already limited. (1)
- Northern climates and winter: In many locations, seasonal UVB is too weak for reliable vitamin D synthesis for part of the year.
- Older age: Aging skin is less efficient at producing vitamin D.
- Fat malabsorption: Celiac disease, Crohn's disease, ulcerative colitis, cystic fibrosis, some liver diseases, and other disorders that reduce fat absorption can impair vitamin D absorption. (1)
- Bariatric surgery: Procedures that bypass portions of the small intestine can increase deficiency risk and may require structured monitoring and supplementation.
- Kidney or liver disease: These organs are involved in vitamin D metabolism, and disease can alter vitamin D handling and activation.
- Certain medicines: Glucocorticoids and some anticonvulsant, weight-loss, and cholesterol-lowering medications can affect vitamin D status or metabolism. (1)
- Obesity: People with obesity often have lower circulating 25(OH)D levels. NIH notes that greater amounts of subcutaneous fat can sequester more vitamin D even though obesity does not prevent the skin from making it. (1)
People with darker skin are often described as automatically needing vitamin D testing, but current guidance is more nuanced. The Endocrine Society specifically recommends against routine screening based only on dark complexion or obesity in otherwise healthy people. (2)
Application: Testing makes the most sense when there is a real clinical reason, such as suspected osteomalacia, abnormal calcium or phosphate findings, osteoporosis or fracture risk, malabsorption, bariatric surgery, chronic kidney or liver disease, medications that alter vitamin D metabolism, or another condition where your practitioner needs the result to guide care.
Warning Signs of Vitamin D Deficiency
Many people with low vitamin D have no obvious symptoms at all.
When deficiency is prolonged or severe enough to affect bone mineralization, the most established clinical signs include:
- Diffuse bone pain or tenderness
- Proximal muscle weakness, such as difficulty rising from a chair or climbing stairs
- Muscle aches
- Difficulty walking in severe osteomalacia
- Fragility fractures or pseudofractures
- Rickets and impaired bone mineralization in children
- Osteomalacia in adults
Fatigue, low mood, joint discomfort, hair loss, frequent illness, high blood pressure, weight changes, and other vague symptoms are often discussed online as signs of vitamin D deficiency.
Some of these have observational associations with low 25(OH)D, but they are not specific enough to diagnose deficiency. For example, NIH notes that low vitamin D has been associated with depression, yet clinical trials have not consistently shown that supplementation prevents or treats depressive symptoms. (1)
This is why I do not want you diagnosing yourself from a symptom list.
Use symptoms as a reason to ask better questions, not as proof that you need a high-dose supplement.
Cardiovascular Health
Vitamin D has been studied extensively in cardiovascular biology.
One 2014 Circulation study found that 4,000 IU of vitamin D3 daily increased circulating angiogenic myeloid cells in healthy volunteers, while laboratory and animal experiments in the same paper explored mechanisms of vascular repair. (8)
That is interesting mechanistic research, but it is not proof that vitamin D supplementation prevents heart attacks or treats cardiovascular disease.
In fact, current NIH reviews note that observational studies often link lower 25(OH)D with higher cardiovascular risk, while randomized trials have generally not shown that vitamin D supplementation reduces cardiovascular events. (1)
Vitamin D status can still be one piece of a broader heart healthy lifestyle, but it is not a stand-alone heart treatment.
Pain and Quality of Life
Pain and quality of life often go hand in hand.
A 2015 cross-sectional study of 83 women with chronic widespread pain found that those with 25(OH)D below 20 ng/mL reported higher pain scores and worse quality-of-life measures than women with higher levels. (9)
Because this was an observational comparison, it cannot prove that low vitamin D caused the pain or that vitamin D supplementation would fix it.
What it does tell us is that checking nutrient status can be worth considering when chronic widespread pain exists alongside other deficiency risks.
Prostate Cancer
Vitamin D and prostate cancer have produced a complicated body of research, and this is an area where older articles can easily overpromise.
A 2014 nested case-control analysis from the Prostate Cancer Prevention Trial found no association with total prostate cancer risk. Higher 25(OH)D was associated with a lower risk of Gleason 8-10 prostate cancer, while lower-grade findings were inconsistent. (10)
Later reviews summarized by NIH have found mixed results, including studies showing no relationship between vitamin D status and overall prostate-cancer risk. Vitamin D supplementation has not been proven to prevent prostate cancer. (1)
So the practical takeaway is not “take vitamin D to prevent prostate cancer.” It is simply that vitamin D biology remains an active area of cancer research, and deficiency should be corrected for established health reasons.
Juvenile Idiopathic Arthritis
Low vitamin D levels have also been observed in autoimmune and inflammatory conditions, including juvenile idiopathic arthritis.
A study of 152 children, adolescents, and young adults with JIA found lower 25(OH)D levels than in matched controls. Levels were lower in participants with active disease or frequent relapses, and deficient patients had lower bone mineral apparent density. (11)
This was an association study. It does not prove that vitamin D deficiency causes JIA or that supplementation treats the autoimmune disease.
It does reinforce something practical: children with chronic inflammatory disease, limited outdoor activity, medications, or bone-health concerns deserve individualized nutrition and bone-health attention.
Reality check: Vitamin D is powerful, but it is not magic. Correct a true deficiency, support healthy levels, and keep the bigger foundation in place: nourishing food, sleep, movement, stress reduction, prayer, sunlight, and appropriate medical care.
Vitamin D Recommendations & Supplements
Are vitamin D supplements necessary?
Sometimes, absolutely.
But not everyone needs the same dose, the same blood target, or year-round supplementation.
The NIH Recommended Dietary Allowance is 600 IU, or 15 mcg, daily for most adults through age 70 and 800 IU, or 20 mcg, for adults over 70. (1)
The 2024 Endocrine Society guideline made an important distinction between meeting ordinary nutrient needs and taking extra vitamin D for disease prevention. For generally healthy adults under 75, it suggests against routine supplementation above the established dietary reference intake. It suggests empiric supplementation in children and adolescents, adults over 75, pregnancy, and adults with high-risk prediabetes because trials suggest possible benefits in those groups. (2)
The guideline also recommends daily, lower-dose vitamin D rather than intermittent high-dose regimens for adults age 50 and older when vitamin D treatment is indicated. (2)
What does this mean practically?
Use supplements when there is a reason: inadequate intake, limited sunlight, documented deficiency, osteoporosis or osteomalacia risk, pregnancy, older age, malabsorption, bariatric surgery, or another clinical situation where your practitioner recommends them.
But supplements cannot replace the full design God built into natural rhythms: nourishing food, outdoor light, movement, sleep, and seasonal living.
Natural vs. Synthetic Vitamin D
Most conventional vitamin D3 supplements are cholecalciferol made from lanolin, which comes from sheep's wool. Vegan D3 is also available from lichen or other non-animal sources.
Once produced and purified, supplemental cholecalciferol is the same form of vitamin D3 the body uses after skin synthesis. That does not make every supplement equal. Purity, dose accuracy, oxidation, excipients, and third-party testing still matter.
Food-first nutrition remains our preference when practical, but supplementation can be genuinely useful when sunlight and food do not meet the need.
Vitamin D3 vs. Vitamin D2
Both vitamin D2 and D3 can raise vitamin D status, but newer comparative evidence favors D3 for raising total 25(OH)D.
A 2024 systematic review and meta-analysis of 20 comparative studies found that vitamin D3 produced a greater increase in total 25(OH)D than vitamin D2 overall. (4)
That is one reason we generally prefer D3 when supplementing.
D3 + K2
For many people, we prefer pairing vitamin D3 with vitamin K2 as part of a broader bone- and mineral-support strategy.
Vitamin D helps increase intestinal calcium absorption. Vitamin K activates proteins involved in calcium handling, including osteocalcin and matrix Gla protein. This biochemical relationship is real.
What is less certain is the popular claim that everyone who takes vitamin D must also take K2 to “keep calcium out of the arteries.”
A 2023 systematic review and meta-analysis of 14 randomized trials found that vitamin K supplementation may slow progression of coronary-artery calcification, but the authors emphasized that more rigorous trials are needed. (5)
So we preserve our practical preference for D3 + K2 without turning it into a universal rule.
There are several forms of K2, including MK-4 and MK-7. MK-7 has a longer circulating half-life and is commonly used in supplements.
Application: If you take warfarin or another medication affected by vitamin K intake, do not start K2 without medical guidance. Consistency of vitamin K intake matters with warfarin therapy.
Note on Bone Health & Steroids
Vitamin D supports calcium absorption, muscle function, and bone mineralization. Prolonged deficiency can contribute to rickets in children and osteomalacia in adults. (1, 7)
Long-term glucocorticoid use increases fracture and osteoporosis risk. The American College of Rheumatology recommends optimizing age-appropriate calcium and vitamin D intake, along with lifestyle measures, for people beginning or continuing chronic glucocorticoid therapy. (6)
For bone health, do not think only about vitamin D.
Think whole lifestyle:
- Vitamin D
- Vitamin K from food and, when appropriate, K2 supplementation
- Calcium-rich foods
- Magnesium
- Adequate protein
- Weight-bearing exercise
- Resistance training
- Regular outdoor time
- Avoiding smoking and excess alcohol
How Much Is Too Much?
Vitamin D is fat-soluble, so more is not always better.
The NIH tolerable upper intake level for adults is 4,000 IU, or 100 mcg, per day from all sources unless a healthcare professional is intentionally using a higher dose to treat deficiency. (1)
Vitamin D toxicity usually comes from excessive supplemental intake, not sunlight. It can cause hypercalcemia, nausea, vomiting, weakness, dehydration, excessive thirst and urination, kidney stones, kidney injury, and in extreme cases cardiac rhythm problems. (1)
High-dose supplementation should have a purpose, a duration, and appropriate follow-up.
Vitamin D-Rich Foods
Sunlight can contribute substantially to vitamin D status when UVB is available, but food matters too.
Naturally vitamin D-rich foods are relatively limited. Good choices include:
- Wild-caught salmon
- Trout
- Sardines
- Mackerel
- Cod liver oil
- UV-exposed mushrooms
- Pasture-raised egg yolks, which provide smaller amounts
- Beef liver, which provides smaller amounts
- Grass-fed dairy, if tolerated and if vitamin D is naturally present or the product is fortified
- Fortified foods when needed
We prefer whole-food sources whenever possible, especially wild-caught fish and pastured animal foods.
If you eat a plant-based diet, vitamin D may take more planning. UV-exposed mushrooms provide vitamin D2, while fortified foods and vegan D3 supplements can help fill gaps.
Because vitamin D is fat-soluble, taking a vitamin D supplement or eating vitamin D-rich foods with a meal that contains some fat can support absorption. NIH notes that fat in the gut enhances vitamin D absorption, although vitamin D can still be absorbed without it. (1)
Application: Build the plate first. Use food to supply vitamin D along with protein, omega-3 fats, minerals, and other nutrients, then supplement strategically when the need is still there.
Vitamin D Deficiency FAQs
What are the most common signs of vitamin D deficiency?
Many people have no obvious symptoms. More significant or prolonged deficiency can cause bone pain, muscle weakness, muscle aches, difficulty walking, poor bone mineralization, osteomalacia in adults, and rickets in children. Fatigue and low mood are possible but nonspecific. (1, 7)
What blood test checks vitamin D levels?
The standard marker is serum 25-hydroxyvitamin D, or 25(OH)D. It reflects vitamin D from skin production, food, and supplements and is the main laboratory measure used to assess vitamin D status. (1)
What vitamin D level is considered low?
The NIH Food and Nutrition Board considers less than 30 nmol/L, or 12 ng/mL, associated with deficiency; 30 to less than 50 nmol/L, or 12 to less than 20 ng/mL, generally inadequate; and 50 nmol/L, or 20 ng/mL, or higher adequate for most healthy people. The Endocrine Society's 2024 prevention guideline no longer defines universal blood targets for disease prevention and advises against routine testing in healthy people without another indication. (1, 2)
Should everyone get a vitamin D blood test?
No. Current Endocrine Society guidance suggests against routine 25(OH)D screening in generally healthy adults. Testing is more useful when the result will change care, such as suspected osteomalacia, abnormal calcium or phosphate levels, malabsorption, bariatric surgery, osteoporosis or fracture concerns, kidney or liver disease, or medications that affect vitamin D metabolism. (2)
How much sun do I need for vitamin D?
There is no universal number of minutes. Vitamin D production depends on skin pigmentation, season, latitude, time of day, cloud cover, age, clothing, and exposed skin surface. Get regular outdoor light, avoid burning, and do not assume a fixed sun timer guarantees an adequate vitamin D level. (1)
Can I get vitamin D on a cloudy day?
Some ultraviolet radiation reaches the ground through clouds, but UVB available for vitamin D synthesis varies substantially with weather, season, latitude, and time of day. Cloudy winter days in northern climates may provide little useful UVB.
Can sunscreen cause vitamin D deficiency?
Sunscreen can reduce vitamin D-producing UVB under controlled conditions, but typical real-world use does not eliminate all cutaneous vitamin D production. NIH notes that most people do not apply enough sunscreen, cover every exposed area, or reapply perfectly. Sunscreen should not automatically be blamed for deficiency. (1)
Is vitamin D3 better than vitamin D2?
Both can raise vitamin D status, but a 2024 systematic review and meta-analysis found that D3 raised total 25(OH)D more effectively than D2 overall. That is why we generally prefer D3 when supplementation is needed. (4)
Should I take vitamin D with K2?
We often prefer D3 with K2 because the nutrients participate in complementary aspects of calcium and bone metabolism. However, evidence does not establish that every person taking vitamin D must also take K2. If you take warfarin or another vitamin K-sensitive medication, do not start K2 without medical guidance. (5)
Can too much vitamin D be harmful?
Yes. Excessive supplemental vitamin D can cause hypercalcemia and serious kidney, gastrointestinal, neurologic, and cardiac problems. The adult tolerable upper intake level is 4,000 IU per day unless a clinician is intentionally using a higher amount for treatment. (1)
Who is most at risk for vitamin D deficiency?
Higher-risk groups include people with limited UVB exposure, darker skin pigmentation, older adults, people with fat-malabsorption disorders, people who have had bariatric surgery, people with obesity, and those taking medications or living with liver or kidney conditions that alter vitamin D metabolism. (1)
Resources & References
- National Institutes of Health Office of Dietary Supplements. “Vitamin D Fact Sheet for Health Professionals.” NIH Office of Dietary Supplements.
- Demay MB, Pittas AG, Bikle DD, et al. “Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline.” Journal of Clinical Endocrinology & Metabolism. 2024;109(8):1907-1947. PubMed.
- American Academy of Dermatology. “Vitamin D.” American Academy of Dermatology.
- van den Heuvel EGM, Lips P, Schoonmade LJ, Lanham-New SA, van Schoor NM. “Comparison of the Effect of Daily Vitamin D2 and Vitamin D3 Supplementation on Serum 25-Hydroxyvitamin D Concentration and Importance of Body Mass Index: A Systematic Review and Meta-Analysis.” Advances in Nutrition. 2024;15(1):100133. doi:10.1016/j.advnut.2023.09.016.
- Li T, Wang Y, Tu WP. “Vitamin K Supplementation and Vascular Calcification: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.” Frontiers in Nutrition. 2023;10:1115069. doi:10.3389/fnut.2023.1115069.
- Humphrey MB, Russell L, Danila MI, et al. “2022 American College of Rheumatology Guideline for the Prevention and Treatment of Glucocorticoid-Induced Osteoporosis.” Arthritis Care & Research. 2023;75(12):2405-2419. doi:10.1002/acr.25240.
- Minisola S, Colangelo L, Pepe J, et al. “Osteomalacia and Vitamin D Status: A Clinical Update 2020.” JBMR Plus. 2021;5(1):e10447. PubMed.
- Wong MSK, Leisegang MS, Kruse C, et al. “Vitamin D Promotes Vascular Regeneration.” Circulation. 2014;130(12):976-986. doi:10.1161/CIRCULATIONAHA.114.010650.
- Kuru P, Akyuz G, Yagci I, Giray E. “Hypovitaminosis D in Widespread Pain: Its Effect on Pain Perception, Quality of Life and Nerve Conduction Studies.” Rheumatology International. 2015;35(2):315-322. doi:10.1007/s00296-014-3099-7.
- Schenk JM, Till CA, Tangen CM, et al. “Serum 25-Hydroxyvitamin D Concentrations and Risk of Prostate Cancer: Results From the Prostate Cancer Prevention Trial.” Cancer Epidemiology, Biomarkers & Prevention. 2014;23(8):1484-1493. PubMed.
- Stagi S, Bertini F, Cavalli L, et al. “Determinants of Vitamin D Levels in Children, Adolescents, and Young Adults With Juvenile Idiopathic Arthritis.” Journal of Rheumatology. 2014;41(9):1884-1892. PubMed.
