Should You Have Your Vitamin D Levels Checked?
Before discussing who should consider having their vitamin D levels checked, it is important to first understand the role vitamin D plays in the body.
Vitamin D is essential for bone health because it helps the body absorb and utilize calcium and phosphorus to build and maintain strong bones. One of the most well-known consequences of severe vitamin D deficiency is rickets, a condition that causes soft and weakened bones in children.
Why Vitamin D Is Unique
Vitamin D is somewhat unique compared to many other vitamins because it can be obtained in two primary ways:
- Through dietary intake and supplements
- Through direct sunlight exposure on the skin
When ultraviolet (UVB) rays from sunlight contact the skin, the body can naturally produce vitamin D.
Vitamin D is also a fat-soluble vitamin, meaning it is best absorbed when consumed with fat-containing foods. Unlike water-soluble vitamins, fat-soluble vitamins can accumulate in the body over time. Because of this, excessive amounts can be consumed through supplementation, although toxicity from dietary intake or normal sun exposure is uncommon.
Who Is at Higher Risk for Vitamin D Deficiency?
Several medical conditions and lifestyle factors are associated with an increased risk of vitamin D deficiency.
Gastrointestinal and Malabsorption Conditions
Certain gastrointestinal conditions may impair the absorption of vitamin D, including:
- Cystic fibrosis
- Crohn’s disease
- Celiac disease
- History of weight loss surgery
Because vitamin D absorption depends on healthy digestion and fat absorption, conditions that impair these processes may increase the risk of deficiency.
Kidney and Liver Disease
The kidneys and liver help convert vitamin D into its active hormonal form, calcitriol.
When these organs are not functioning properly, vitamin D activation may become impaired, potentially leading to deficiency.
Parathyroid Disorders
The parathyroid glands help regulate calcium balance within the body. Dysfunction of these glands may contribute to altered regulation of vitamin D and calcium.
Multiple Sclerosis (MS)
Individuals with multiple sclerosis (MS) are often encouraged to maintain adequate or even higher-than-average vitamin D levels.
Some research suggests that maintaining healthy vitamin D status may play a protective role, potentially reducing the risk of developing MS or influencing disease activity.
Because of this, some individuals with MS may require closer monitoring and more individualized supplementation plans.
Obesity
Individuals with obesity, defined as a body mass index (BMI) of 30 or greater, may also have an increased risk of vitamin D deficiency.
Research suggests a complex relationship between obesity and vitamin D status, though scientists are still working to fully understand the connection.
Possible Symptoms of Vitamin D Deficiency
Vitamin D deficiency symptoms can vary widely and may sometimes be subtle or nonspecific.
Possible symptoms may include:
- Muscle aches, weakness, or cramping
- Bone pain
- Fatigue
- Reduced endurance
- Difficulty concentrating or memory changes
- Mood changes or depression
- Poor sleep quality
- Excessive sweating
- Thin or brittle hair
- Slow wound healing
- Frequent infections
- Dizziness
Some studies have also linked low vitamin D levels with cardiovascular disease, high blood pressure, and metabolic concerns, although research in these areas is still evolving.
How Common Is Vitamin D Deficiency?
Vitamin D deficiency is considered very common in the United States.
Research estimates that approximately 42% of U.S. adults may have low vitamin D levels, although prevalence can vary by age, geographic location, skin pigmentation, and seasonal sunlight exposure.
Because sunlight exposure contributes significantly to vitamin D production, deficiency rates are often higher during winter months when daylight hours are shorter.
Additionally, the risk of deficiency tends to increase with age due to changes in skin synthesis, dietary intake, and overall absorption.
Should Everyone Get Their Vitamin D Levels Checked?
Individuals with medical conditions known to affect vitamin D absorption or metabolism should discuss routine monitoring with their healthcare provider.
You may want to discuss testing with your healthcare provider if you:
- Spend very little time outdoors
- Do not regularly consume vitamin D-rich foods
- Have symptoms consistent with a deficiency
- Have medical conditions associated with low vitamin D levels
Ways to Support Healthy Vitamin D Levels
Depending on your individual health status, supportive strategies may include:
- Increasing dietary vitamin D intake
- Spending safe amounts of time outdoors in sunlight
- Taking supplements under medical guidance
- Monitoring symptoms over time
Keeping a symptom log may help you identify whether lifestyle changes are improving how you feel.
The Bottom Line
Vitamin D plays an important role in bone health, immune function, muscle function, and overall wellness.
Because deficiency can sometimes develop gradually and symptoms may be vague, staying informed and discussing concerns with your healthcare provider may help identify low levels earlier and prevent complications over time.
Obesity and vitamin D deficiency also have a particularly complex relationship, which is explored further in the article "Obesity and Vitamin D Deficiency—Correlation vs. Causation."
- Forrest, K. Y. Z., & Stuhldreher, W. L. (2011). Prevalence and correlates of vitamin D deficiency in US adults. Nutrition Research, 31(1), 48–54. https://doi.org/10.1016/j.nutres.2010.12.001
- Holick, M. F. (2007). Vitamin D deficiency. The New England Journal of Medicine, 357(3), 266–281. https://doi.org/10.1056/NEJMra070553
- Munger, K. L., Levin, L. I., Hollis, B. W., Howard, N. S., & Ascherio, A. (2006). Serum 25-hydroxyvitamin D levels and risk of multiple sclerosis. JAMA, 296(23), 2832–2838. https://doi.org/10.1001/jama.296.23.2832
- National Institutes of Health Office of Dietary Supplements. (2025). Vitamin D fact sheet for consumers. https://ods.od.nih.gov/factsheets/VitaminD-Consumer/
- Pereira-Santos, M., Costa, P. R. F., Assis, A. M. O., Santos, C. A. S. T., & Santos, D. B. (2015). Obesity and vitamin D deficiency: A systematic review and meta-analysis. Obesity Reviews, 16(4), 341–349. https://doi.org/10.1111/obr.12239
- U.S. Preventive Services Task Force. (2021). Vitamin D deficiency in adults: Screening.https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/vitamin-d-deficiency-screening
- Williams, S., Malatesta, K., & Norris, K. (2009). Vitamin D and chronic kidney disease. Ethnicity & disease, 19(4 Suppl 5), S5–11. https://pmc.ncbi.nlm.nih.gov/articles/PMC2878736/
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