Vitamin D (25-hydroxyvitamin D) is essential for calcium absorption, immune function, and bone health.

Diagnostic Value: This test evaluates overall vitamin D status and helps diagnose deficiency, osteomalacia, or osteoporosis.

Clinical Importance: Deficiency contributes to fatigue, bone pain, immune weakness, and increased inflammation.

Symptom Correlation: Low levels may cause muscle weakness, joint pain, and susceptibility to infections.

Vitamin D testing is vital for assessing both metabolic and immune well-being.