Where your DNA places you among other people, and the studies behind it.
Not tailored to your result, and not medical advice
Test Only If You Have Reason To: A blood test can confirm deficiency if you have risk factors such as limited sun exposure, darker skin, or a condition affecting absorption. Routine testing of healthy adults is not recommended by current guidelines, so this is a question of whether it applies to you rather than something everyone needs. Endocrine Society
Get Sensible Sun and Dietary Sources: Modest sun exposure, plus foods like fatty fish, egg yolks, and fortified milk, helps maintain status without burning. People with darker skin or who live at high latitudes synthesize less and may rely more on diet and supplements. NIH Office of Dietary Supplements
More Is Not Better: Sunlight, oily fish, egg yolks and fortified foods are the ordinary routes to adequate vitamin D. For adults who are already replete, large trials show no benefit from high-dose supplements for cancer or heart disease, and very high intakes can do harm. More is not better here. NEJM (VITAL trial)
How much of this is genetic?
Genetics explains 40% of why people differ in this trait. The rest is environment, daily habits and chance.
Heritability estimate: Nutrients 2022 review (PMC9606877)
Background and further reading
Vitamin D is a fat-soluble secosteroid that the body converts into a hormone supporting calcium absorption and bone health, with roles in immune function as well. Circulating 25-hydroxyvitamin D [25(OH)D] is the standard biomarker of status. Guideline bodies disagree on cutoffs: the U.S. Institute of Medicine treats 20 ng/mL (50 nmol/L) as adequate for nearly everyone, while the Endocrine Society's earlier guidance used 30 ng/mL; levels below about 12 ng/mL signal deficiency [1].
Genetic Basis: A genome-wide study of 417,580 people identified 143 loci tied to 25(OH)D concentration, with the strongest signals near GC (vitamin D binding protein), DHCR7 (7-dehydrocholesterol reductase), CYP2R1 (hepatic 25-hydroxylase), and CYP24A1 (24-hydroxylase) [2]. These genes govern synthesis, transport, and breakdown of vitamin D. Twin and family estimates of heritability range widely (roughly 30-70%, often near 40%, and higher in winter when sun exposure is lowest); common variants explain a smaller share, and roughly half of the genetic signal may reflect inherited differences in skin pigmentation and sun-seeking behavior [2].
Environmental Factors: UVB sunlight on the skin is the main source of vitamin D for most people, supplemented by diet and oral supplements, both of which reliably raise circulating levels [3]. Latitude, season, skin pigmentation, sunscreen use, time outdoors, body fat, and age all shape status. Notably, large trials such as VITAL found that supplementing already-healthy adults did not lower their risk of cancer or major cardiovascular events [4].
The published research behind your score, and the variants it draws on.
28 published scores from 7 studies
The vitamin D levels score combines 28 polygenic scores drawn from 7 published studies.
These traits are influenced by some of the same genes and variants as this one
Content updated August 2026.
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