Can Vitamin D Test help with skin aging?

A Vitamin D test can identify deficiency, which is linked to skin health, but evidence for a direct anti-aging effect is limited to mechanistic and observational studies. Vitamin D influences keratinocyte proliferation, barrier function, and inflammation, yet RCTs do not confirm that supplementation slows skin aging in well-nourished individuals. Testing is useful to detect insufficiency, but relying solely on it for skin aging is not evidence-based. Caveat: Do not replace sun protection; prioritize adequate vitamin D from sun or diet.