5 Surprising Signs You May Be Vitamin D Deficient
Updated on May 11, 2026
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5 Surprising Signs You May Be Vitamin D Deficient
Certain symptoms may suggest your vitamin D levels are too low. Here are 5 signs to watch out for.
An estimated 35 percent of Americans are deficient in vitamin D, an essential vitamin that plays an important role in keeping bones, muscles, and the immune system healthy.
One way to get vitamin D is through sun exposure, but since ultraviolet rays can cause skin cancer, the American Academy of Dermatology advises against this method, urging sun protection whenever you’re outdoors. Instead, the organization recommends getting vitamin D through diet. Several foods are good sources of vitamin D, such as fatty fish, fortified breakfast cereal, and mushrooms exposed to UV light.
Healthy nonpregnant adults younger than age 71 need at least 15 micrograms (mcg), which is equivalent to 600 international units (IU) of vitamin D per day, through fortified foods, or if needed, supplementation. Dosage recommendations can vary depending on factors such as age and life stage.
How do you know if you’re vitamin D deficient? The best way is through a simple blood test, which your primary care physician can do. Your doctor will also advise if you should take a supplement and what dosage may be appropriate. That said, certain symptoms may suggest your vitamin D levels are too low.
1. Fatigue
Feeling fatigued and sluggish is probably the most common sign of vitamin D deficiency, says Ann Louise Gittleman, PhD, author of Radical Longevity, who is based in Coeur d’Alene, Idaho. One study of 300 adults aged 18 to 60 found a strong inverse relationship between vitamin D deficiency and fatigue. In other words, the lower the level of vitamin D, the higher the level of fatigue participants reported.
Vitamin D supplements may help reverse the trend: Another study of people with vitamin D deficiency found that vitamin D treatment improved participants’ symptoms, including fatigue, after two months of supplementation.
2. Broken Bones and Stress Fractures
“Bone fractures that don’t heal quickly are another sign [of vitamin D deficiency],” Dr. Gittleman says.
That’s because one of the critical roles of vitamin D is to help the body absorb calcium, which supports bone health. Research indicates that adequate vitamin D and calcium levels can promote healthy bones and help prevent osteoporosis.
A meta-analysis found that supplementing with vitamin D (specifically, vitamin D3) and calcium reduced the incidence of both falls and fractures in the study participants.
People tend to stop building bone mass around age 30, so adequate vitamin D intake is important to keep the bones in good condition as you age.
3. Low Immunity
Another important function of vitamin D is keeping the immune system running adequately and appropriately.
Research has found a link between lower levels of vitamin D and an increased risk of infection. Before antibiotics became available, sunlight and sun lamps were used to treat infections like tuberculosis.
One study of 199 adults found that the prevalence of respiratory illnesses was highest in those who were most deficient in vitamin D. Conversely, higher levels of vitamin D correlated with less frequent respiratory infections.
“Quite frankly, [the link is] huge,” Gittleman says, noting her own clinical care experiences. She notes if you seem to be catching every cold, flu, and virus that comes along, you may be deficient in vitamin D, and this is something to discuss with your primary care provider. They can test your vitamin D levels and evaluate you for other potential causes that may be impeding your immune function.
4. Muscle Pain and Achiness
In some cases, vitamin D deficiency can cause muscle pain and achiness. As mentioned, a vitamin D status test can help determine whether this vitamin deficiency may be a root of these symptoms.
If it is, your doctor might recommend taking vitamin D supplements. One study found that physical therapy along with vitamin D supplementation was more effective at reducing pain than physical therapy alone.
5. Hair Loss
Research has found a correlation between alopecia, or hair loss, and low vitamin D.
Vitamin D plays an important role in developing healthy hair follicles so if you have hair loss and are vitamin D deficient your doctor might suggest supplementation.
EDITORIAL SOURCES
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Resources
- Vitamin D Deficiency. Cleveland Clinic. August 2, 2022.
- Vitamin D Stats and Facts. American Academy of Dermatology Association. February 11, 2025.
- Vitamin D: Fact Sheet for Consumers. Office of Dietary Supplements. November 8, 2022.
- Acharya SK et al. Evaluation of Vitamin D Deficiency and Its Association With Fatigue and Muscle Weakness in the General Population. European Journal of Cardiovascular Medicine. April 22, 2025.
- Albasheer O et al. Effects of Vitamin D Supplementation on Symptoms and Clinical Outcomes in Adults With Different Baseline Vitamin D Levels: An Interventional Study. Journal of Health, Population and Nutrition. May 29, 2025.
- Voulgaridou G et al. Vitamin D and Calcium in Osteoporosis, and the Role of Bone Turnover Markers: A Narrative Review of Recent Data From RCTs. Diseases. February 8, 2023.
- Kong SH et al. Effect of Vitamin D Supplementation on Risk of Fractures and Falls According to Dosage and Interval: A Meta-Analysis. Endocrinology and Metabolism. April 25, 2022.
- Osteoporosis: Symptoms and Causes. Mayo Clinic. December 17, 2025.
- Li W et al. Vitamin D Deficiency and Respiratory Health: A Narrative Review Bridging Gaps in Public Health Through Innovative Strategies and Sustainable Solutions. Journal of Infection and Public Health. January 2026.
- Vitamin D. The Nutrition Source. March 2023.
- Ried K et al. Prevalence of Vitamin-D Deficiency and Respiratory Tract Infections in Adults: A Cross-Sectional Study. Advances in Integrative Medicine. December 2025.
- Ali M et al. Combined Effect of Vitamin D Supplementation and Physiotherapy on Reducing Pain Among Adult Patients With Musculoskeletal Disorders: A Quasi-Experimental Clinical Trial. Frontiers in Nutrition. October 4, 2021.
- Zubair Z et al. Prevalence of Low Serum Vitamin D Levels in Patients Presenting With Androgenetic Alopecia: A Review. Cureus. December 15, 2021.
- Fisher J. Vitamins, Minerals, and Hair Loss: Is There a Connection? Harvard Health Publishing. April 22, 2024.
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