Vitamin D (25-OH)
What is it?
Vitamin D regulates calcium and phosphorus metabolism and affects immunity and bones. Deficiency is common, especially in northern latitudes.
Normal ranges
Optimal: 30–60 ng/mL. Insufficient: 20–30. Deficient: < 20.
Units: ng/mL
Causes of deviations
Low levels:
Lack of sun exposure, poor diet, malabsorption.
High levels:
Vitamin D supplement overdose.
When to see a doctor
If deficient — for dose adjustment; if > 100 — possible toxicity.
This information is for educational purposes and does not replace medical advice.
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