Vitamin D — 25-Hydroxyvitamin D — 60-Second Protocol
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lab guide · 2026-10-17
Your skin makes vitamin D in sunlight — and clouds, age, darker skin and sunscreen all cut how much.
The 25-hydroxy vitamin D test is the most accurate way to measure how much vitamin D is in your body. Your skin makes vitamin D in sunlight, and it also comes from food and supplements; it is needed for bones and for the immune system.
The protocol
| Units | ng/mL |
| Standard range | 20–40 ng/mL recommended by many experts; 30–50 ng/mL by others — ranges vary by lab |
| <12 | at risk of vitamin D deficiency, per the Food and Nutrition Board (NIH ODS) |
| >50 | can be associated with adverse effects, per the Food and Nutrition Board (NIH ODS) — discuss with your clinician, and do not keep taking vitamin D supplements without their advice |
| 12–20 | some people are potentially at risk of inadequacy, per the Food and Nutrition Board (NIH ODS) |
| 20–50 | adequate for bone health and overall health in most people, per the Food and Nutrition Board (NIH ODS) |
| Food | fatty fish such as trout, salmon, tuna and mackerel are among the best natural sources; many foods are fortified |
| High | a higher-than-normal level is most commonly caused by taking too much vitamin D and can raise blood calcium |
| Sunlight | your body makes vitamin D when bare skin is exposed to the sun; clouds, smog, older age, darker skin and sunscreen reduce how much |
| Supplement | the right amount varies by person — discuss with a clinician before starting |
Testing first is the whole point — a finger-prick kit gets you the number before anything changes.
Vitamin D (25-OH) Home Test
A finger-prick home test for 25-hydroxyvitamin D, the marker clinicians use to judge vitamin-D status.
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Full transcript
Your skin makes vitamin D in sunlight — and clouds, age, darker skin and sunscreen all cut how much. The twenty-five-hydroxy test is the most accurate measure. Twenty to fifty nanograms per millilitre is adequate for most people; under twelve is at risk of deficiency. Above fifty can bring adverse effects, most often from taking too much. Supplementing is a clinician conversation. agegen.ai. Generate your prime age! ~~ Mr. Age
Sources
- https://medlineplus.gov/lab-tests/vitamin-d-test/
- https://medlineplus.gov/ency/article/003569.htm
- https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
- https://ods.od.nih.gov/factsheets/VitaminD-Consumer/
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