What is a normal vitamin D (25-hydroxyvitamin D) level in a 14-year-old female?

Normal Vitamin D (25-OH) Levels in a 14-Year-Old Female

A normal vitamin D (25-hydroxyvitamin D) level for a 14-year-old female should be above 30 ng/mL (75 nmol/L), with an optimal range between 30-44 ng/mL for best health outcomes. 1

Recommended Reference Ranges

• Based on current evidence, a 25(OH)D level of 30-44 ng/mL provides optimal benefits for musculoskeletal health, cardiovascular health, and cancer prevention 1
• Levels below 20 ng/mL are considered vitamin D deficiency 2
• Levels between 21-29 ng/mL are considered vitamin D insufficiency 2
• An upper safety limit of 100 ng/mL has been established, though there's no evidence that levels above 50 ng/mL provide additional benefits compared to the 30-44 ng/mL range 1

Importance of Maintaining Adequate Vitamin D Levels

• Adequate vitamin D levels are essential for:
  • Normal bone mineralization and development, particularly important during adolescence 1
  • Prevention of secondary hyperparathyroidism 3
  • Optimal calcium absorption from the intestine 4
  • Potential reduction in risk of autoimmune diseases, common cancers, and cardiovascular disease 2

Special Considerations for Adolescents

• Adolescents may require higher vitamin D supplementation to achieve target levels compared to adults 5
• In a study of adolescents aged 13 ± 2 years, a daily dose of 2000 IU of vitamin D3 was required to raise 25(OH)D levels ≥20 ng/mL in 96% of participants 5
• Factors affecting vitamin D status in adolescents include:
  • Baseline 25(OH)D level 5
  • Body mass index (BMI) 5
  • Sex (boys may have slightly higher levels than girls in some populations) 5
  • Sun exposure and skin pigmentation 1

Measurement Considerations

• Serum 25(OH)D is the appropriate biomarker for vitamin D status 2
• Measurement uncertainty related to 25(OH)D assays must be taken into account 1
• Choosing a threshold of 30 ng/mL helps ensure the patient has a true concentration >20 ng/mL, accounting for laboratory variability 1
• Seasonal variation should be considered when interpreting results, as levels may fluctuate throughout the year 1

Clinical Implications

• If levels are below 30 ng/mL, supplementation should be considered 1
• For adolescents with levels between 20-30 ng/mL, adding 1000 IU of vitamin D3 daily may be appropriate 1
• For more significant deficiency (<20 ng/mL), higher correction doses may be needed initially, followed by maintenance therapy 1
• As a rule of thumb, an intake of 1,000 IU vitamin D/day results in an increase of approximately 10 ng/mL in 25(OH)D levels, though individual responses vary 1