Vitamin-D Selbsttest: which supplements make sense?

The provided knowledge contexts do not contain information on Vitamin D self-tests or specific supplements. In general, a Vitamin D self-test (25(OH)D blood test) can give a baseline but is often less reliable than lab-based tests. Supplementation should be guided by measured levels. Common supplements include vitamin D3 (cholecalciferol), often paired with vitamin K2 (MK-7) – evidence for added benefit of K2 is moderate. Magnesium is also needed for vitamin D activation. Without medical supervision, high doses (>4000 IU/day) are not recommended. Evidence for supplementation in individuals with normal levels is weak; in confirmed deficiency, vitamin D3 is sensible. Caveat: self-tests alone do not replace clinical diagnosis. The contexts cover other topics (COMT, MTHFR, MC4R, etc.) and do not directly support this answer.