Primary Research · 2011
Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline
Holick et al. · Journal of Clinical Endocrinology & Metabolism, 2011
Key finding
Endocrine Society guideline. Defines deficiency (<20 ng/mL), insufficiency (20-30), and sufficiency thresholds.
Read the paper
Open on PubMedhttps://pubmed.ncbi.nlm.nih.gov/21646368/
Cited in 3 guides
Roundup
Best Multivitamin for Adults Over 50: What to Actually Look For
Over 50, nutrient absorption declines and specific needs change (B12, D, calcium, iron). Most senior multivitamins get it wrong. Here's what to check.
Roundup
Best Vitamin D Supplements 2026: Ranked by Clinical Evidence
42% of adults are deficient. Learn which D3 form, dose, and brand actually raises blood levels — with cofactor guidance and lab-verified picks.
Review
Vitamin D3 vs D2: The Science Behind the 87% Gap
D3 raises blood levels 87% more effectively than D2 — and your prescription vitamin D might be the inferior form. Here's what to know.
About this page
Formulate maintains a registry of clinical studies cited across its guides and evidence grades. This page links the study metadata to the content that cites it — one canonical entry per landmark study.
The full citation chain is public so readers can verify claims without hunting through individual guide pages. Browse all cited studies →
Note: Study summaries on this page are editorial interpretations of the research. Always consult the primary source before drawing clinical conclusions.