Vitamin D3 (cholecalciferol) is essential for calcium absorption, bone mineralization, and immune function.

Deficiency can lead to rickets in children, osteomalacia in adults, osteoporosis, and increased fracture risk.

Clinical uses include:

Diagnosing Vitamin D deficiency or insufficiency.

Monitoring patients with bone disorders, chronic kidney disease, or malabsorption syndromes.

Evaluating nutritional status in elderly, pregnant women, and individuals with limited sun exposure.

Supporting management of osteoporosis and metabolic bone disease.

Often performed alongside Calcium, Phosphorus, and Parathyroid Hormone (PTH) tests for comprehensive evaluation.

Analyte: 25‑hydroxyvitamin D3 (calcidiol) in serum (ng/mL).

Normal Range (varies by lab):

Deficiency: <20 ng/mL.

Insufficiency: 20–30 ng/mL.

Sufficient: 30–100 ng/mL.

Abnormal Findings:

Low Vitamin D3: Suggests deficiency due to poor intake, lack of sunlight, malabsorption, or chronic illness.

High Vitamin D3: May occur with excessive supplementation, leading to hypercalcemia.

Clinical Use:

Provides a direct marker of Vitamin D status.

Helps guide diagnosis, supplementation, and monitoring of bone and metabolic health.

Supports endocrinology, orthopedics, nephrology, and general medicine evaluations.