Vitamin D (25-OH) (25(OH)D)
Also known as: 25(OH)D
25-hydroxy vitamin D is the standard biomarker of vitamin D status. Sub-optimal levels are common and contribute to fatigue, mood symptoms, immune function, and bone-density changes.
What Vitamin D (25-OH) measures
25-hydroxyvitamin D (25-OH-D) is the storage form of vitamin D and the standard marker of vitamin D status. It integrates dietary, supplemental, and sunlight-derived vitamin D over the preceding weeks.
Clinical significance
Vitamin D is a steroid prohormone with receptors throughout the body — bone, immune, muscle, hormonal, and cardiovascular tissues. Insufficiency is associated with bone loss, immune dysregulation, mood symptoms, fatigue, muscle weakness, and impaired testosterone production in men.
How oMeds reviews it
25-OH-D is reviewed at baseline and re-checked at recalibration in every optimization pathway. Provider-reviewed targets exceed standard 'sufficient' thresholds — symptom resolution and adjacent marker improvement most consistently land at 40-60 ng/mL.
Standard clinical reference intervals
Lab-reported reference ranges from established standards bodies. These are diagnostic thresholds — they do not represent optimization targets.
Source: Endocrine Society 2011 Clinical Practice Guideline (sufficient ≥30 ng/mL)
oMeds optimization targets
Editorial bands that inform provider-reviewed conversations. These are wellness targets, not diagnostic thresholds.
Provider-reviewed wellness consistently targets 40-60 ng/mL where symptomatic benefit accrues without approaching toxicity. Levels above 100 ng/mL warrant dose reduction.
oMeds optimization ranges are editorial targets that inform conversations with a licensed provider. They are NOT diagnostic thresholds and do not replace lab reference ranges.
Vitamin D (25-OH) — frequently asked
How much vitamin D should I supplement?
Dose is individualized to baseline 25-OH-D, body composition, sun exposure, and absorption. Provider review starts low for sufficient patients and uses higher loading doses only when baseline is deficient.
Can I get enough from sun?
Skin synthesis depends on latitude, season, time of day, skin tone, age, and sunscreen use. Many adults in northern latitudes cannot reach optimization targets from sun alone and require supplementation.
Source literature
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Conditions this biomarker informs
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