Vitamin D, 25-Hydroxy

Also written 25(OH)D

NutrientsMeasured in ng/mL

What it measures

The circulating storage form of vitamin D, reflecting combined intake and sun exposure over recent weeks.

Why it matters

Genuine deficiency causes real bone disease and is common, particularly at higher latitudes and in people with darker skin.

Where the claimed ranges actually sit

Measured in ng/mL. Each row is one claim about where your result should fall.

What a laboratory reportsWhat a seller markets as “optimal”

Laboratory reference range> 20 ng/mL

Two major expert bodies publish different sufficiency thresholds

50–80 ng/mLC50–80 ng/mL

Supplement sellers, functional medicine, and longevity platforms

›View as table

Claim	Range	Source
Laboratory reference range	> 20 ng/mL	Two major expert bodies publish different sufficiency thresholds
50–80 ng/mL	50–80 ng/mL	Supplement sellers, functional medicine, and longevity platforms

Where the sources disagree

Two respected expert bodies set the sufficiency threshold at 20 and 30 ng/mL respectively, which alone should signal that precision here is illusory. Commercial ranges then push to 50–80, a target that no outcome trial supports. The honest summary is that correcting genuine deficiency is worthwhile and cheap, and that chasing a high-normal number has repeatedly failed to produce the benefits its marketing promises.

The marketed ranges, examined

Each claim gets its strongest possible case before it gets its criticism. Several of these are substantially correct.

50–80 ng/mL

Promoted by supplement sellers, functional medicine, and longevity platforms

CConfounded

The strongest case for it

Observational data link low vitamin D to a long list of poor outcomes, and higher levels are associated with better health across many cohorts.

What it leaves out

Large randomized supplementation trials have largely failed to reproduce those observational benefits for cancer, cardiovascular disease, and mortality. Low vitamin D appears to be substantially a marker of poor health (of illness, obesity, and not going outside) rather than a cause of it. This is the single most reliable supplement-selling range in the registry.

Before you act on your result

Reverse causation is a serious confounder: illness and obesity lower measured vitamin D.
Toxicity is possible with sustained high-dose supplementation; more is not safer.
Seasonal variation is large; compare like-for-like months when tracking.

Last reviewed July 28, 2026How we grade evidence and attribute claims →

More in Nutrients

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