Markers · Vitamins
A vitamin D of 30, just inside the range. Vitamin D, read against the rest of you.
What vitamin D measures, what it does in the body, why it's tested, and the two ranges it's read against. Everything said about the marker here comes from Merlin's own biomarker catalogue.
What vitamin D is
Vitamin D 25-OH is the primary circulating form of vitamin D and the best indicator of overall vitamin D status in the body. It reflects the combined contribution of sun exposure, dietary intake, and supplementation. Low levels are associated with bone disease, immune dysfunction, increased risk of cardiovascular disease, and metabolic disorders, while very high levels can indicate toxicity.
What it does in the body
Vitamin D functions as a steroid hormone regulating calcium and phosphorus absorption to maintain bone mineralization and skeletal integrity. It modulates immune function, reduces systemic inflammation, supports neuromuscular function, influences insulin secretion, and regulates cell growth and differentiation through nuclear receptor signaling in nearly every tissue in the body.
Why it's tested
Testing is used to diagnose vitamin D deficiency or insufficiency, monitor supplementation therapy, assess bone health risk, evaluate malabsorption syndromes, and screen individuals at high risk including the elderly, those with limited sun exposure, darker skin tones, obesity, or chronic kidney or liver disease.
The two ranges
The reference range reflects population statistics. The target reflects physiology.
- Lab reference range
- 20-50 ng/mL (50-125 nmol/L); Deficiency: <20 ng/mL; Insufficiency: 20-29 ng/mL; Toxicity risk: >100 ng/mL
- Functional target
- 40-60 ng/mL (100-150 nmol/L)
Those are different numbers, and you deserve to know which one you're looking at. Merlin reads your result against both.
Where this lives
A Field Guide to Immune Resilience
The field guide that covers vitamin D in depth, whole and public.
In a real read
Vitamin D is in the real Cardiovascular read on this site at 30 ng/mL, which the read calls "at the lab floor" and names as one of two "low-cost levers". A number inside the lab's range still gets read, and in this one it's flagged as something to act on.
A real Cardiovascular surface from a real anonymized panel: the score, the narrative, the layers underneath. Yours will be built the same way, on your own numbers.
Educational context for your conversations with your licensed healthcare provider, not a diagnosis or a treatment plan. Merlin reads results; it doesn't diagnose.
Bring the panel this number came from. Merlin reads it against everything else you have, every system and every year, then shows you what it means and what's worth finding out next. Start with your first month.