Myths vs facts: Vitamin D Test and fatigue

The myth that a vitamin D test alone can pinpoint the cause of fatigue is misleading. Fact: Vitamin D deficiency can contribute to fatigue, especially in severe deficiency (< 12 ng/ml). However, fatigue is a nonspecific symptom with many potential causes (sleep deprivation, stress, iron deficiency, thyroid issues, depression). Evidence from randomized trials on vitamin D supplementation for fatigue is mixed: correction helps in deficient individuals, but no benefit in those with normal levels. Routine vitamin D testing for fatigue without specific risk factors is not recommended by many guidelines. Testing is reasonable in risk groups (elderly, dark skin, low sun exposure, obesity). Limitations include seasonal variation and that serum levels do not fully reflect tissue status. Conclusion: Vitamin D testing can be part of a workup, but not a standalone diagnostic for fatigue.