Vitamin D
The storage form of vitamin D - core nutrient status marker, deficient in ~40% of adults.
How Vitamin D ranges relate
The standard lab range vs the optimization-focused target. Illustrative trajectory shows what a 12-week improvement pattern looks like — not real user data.
What Vitamin D Measures
25-hydroxyvitamin D (25-OH-D) is the circulating storage form of vitamin D and the standard biomarker of vitamin D status. Values <20 ng/mL indicate deficiency; 20–29 insufficiency; 30+ is the standard sufficiency threshold. Optimization-focused practitioners typically target 50–80 ng/mL based on observational data linking higher levels with reduced CVD, cancer, and all-cause mortality.
Vitamin D is fat-soluble and status is driven primarily by sunlight exposure, dietary intake (fatty fish, fortified dairy), and supplementation. Deficiency is shockingly common - 30–50% of adults in temperate latitudes, higher in people with darker skin or limited sun exposure.
What Affects This Biomarker
Vitamin D status is influenced by: sun exposure (UVB), latitude + season, skin pigmentation (darker skin requires more sun), age (older skin makes less D per exposure), body fat (fat-soluble - high adiposity sequesters D), kidney function, and supplementation. Most people need 2000–5000 IU/day oral D3 + K2 to hit 50+ ng/mL.
In the Context of Peptide Protocols
Track at baseline on every protocol - D status affects testosterone, immune function, and bone health independent of any peptide. Re-test 8–12 weeks after starting supplementation to ensure dose is adequate. Pair with calcium, phosphorus, and PTH if values are extreme.
Related Reading
Conditions That Track Vitamin D
Upload any lab PDF and MyProtocolStack maps your values to Vitamin D and 40+ other biomarkers. StackAI interprets the trend in context of your protocol.
Start tracking →Informational only - not medical advice. Reference ranges vary by lab and individual context. Work with a licensed provider to interpret your specific results.