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Vitamin D (25-OH)

Quick answer

What is Vitamin D (25-OH)?

25-hydroxyvitamin D is the storage form and the standard test. Low vitamin D is common in office-bound men and correlates weakly with low testosterone, immune dysfunction, and bone health. Supplementation is cheap and effective when deficient.

Units:
nmol/L
Reference range:
75-150 nmol/L (optimal); 50-75 sufficient
Sample:
Venous blood (serum)
Category
Micronutrients
Units
nmol/L
Reference range
75-150 nmol/L (optimal); 50-75 sufficient

What does a high Vitamin D (25-OH) result mean?

Above 200 nmol/L: over-supplementation. Acute toxicity rare but possible above 250.

What does a low Vitamin D (25-OH) result mean?

Below 50 nmol/L: insufficient. Below 30: deficient. Drivers: indoor lifestyle, latitude, dark skin, obesity (vitamin D sequestered in fat tissue).

Why does Vitamin D (25-OH) matter?

One of the cheapest, most-easily-corrected markers. Test, supplement if low, retest in 3 months.

FAQs

How much vitamin D should I supplement?
1000-4000 IU/day for most men if deficient, with retesting in 3 months. Higher doses warrant clinician oversight.

References

  1. [1]Evaluation, Treatment, and Prevention of Vitamin D DeficiencyEndocrine Society / JCEM
  2. [2]Clinical Methods: The History, Physical, and Laboratory ExaminationsNCBI Bookshelf

Want Vitamin D (25-OH) interpreted in the context of your full panel? Every FORM bloodwork tier covers it, with an MD walking you through the result.

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