Is vitamin D (Vit D) deficiency related to fatigue?

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Last updated: June 5, 2025View editorial policy

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From the Research

Vitamin D deficiency is related to fatigue, and supplementation may help improve energy levels in deficient individuals. The most recent and highest quality study, 1, suggests that a daily vitamin D supplementation with 2000 IU (50 µg) may be considered a simple, effective, and safe dosage to prevent and treat vitamin D deficiency in the adult general population. This study argues that such a dose may improve some health outcomes and is sufficient to raise and maintain serum 25(OH)D concentrations above 50 nmol/L (20 ng/mL) and above 75 nmol/L (30 ng/mL) in >99% and >90% of the general adult population, respectively.

Key Points

  • Vitamin D plays crucial roles in multiple body systems, including muscle function, immune response, and calcium absorption, which explains its connection to energy levels 2, 3, 4
  • The body produces vitamin D when skin is exposed to sunlight, but many people have insufficient sun exposure or other risk factors for deficiency such as darker skin, obesity, or living in northern latitudes 5
  • Supplementation is generally safe, but extremely high doses should be avoided without medical supervision as vitamin D is fat-soluble and can accumulate in the body 5, 1
  • A 25-hydroxyvitamin D blood test can help determine if an individual has a vitamin D deficiency, and supplementation can be tailored to their specific needs 2, 3, 4

Recommendations

  • If you're experiencing unexplained fatigue, ask your healthcare provider for a 25-hydroxyvitamin D blood test to check your levels 2, 3, 4
  • Consider taking a daily vitamin D supplement of 2000 IU (50 µg) to prevent and treat vitamin D deficiency, as recommended by the most recent and highest quality study 1

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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