Self Test Vitamin D What is vitamin D and why measure it: Vitamin D, particularly the form 25-hydroxyvitamin D (25(OH)D), is essential for calcium absorption and bone health, for muscle function, for immune defenses, and for the prevention of certain chronic diseases. Una deficiency can cause fatigue, muscle pain, brittle bones, osteoporosis or rickets in children, as well as increase the risk of infections or autoimmune disorders.|| How the self-test for vitamin D works: It is a rapid home test that assesses whether the concentration of vitamin D is sufficient or deficient. It does not provide a precise numerical value but a qualitative indication. It is based on a small sample of capillary blood and returns the result in about 10-15 minutes.|| Indicative reference values:| Below 20 ng/mL → deficiency|| Between 20 and 30 ng/mL → insufficiency|| Between 30 and 50 ng/mL → optimal level|| Over 100 ng/mL → possible excess or toxicity from overdose|| | When to do it:| In months with low sun exposure (winter and early primavera)|| If on a diet low in foods containing vitamin D or a vegan diet|| In the presence of deficiency symptoms (fatigue, pain, bone fragility)|| During pregnancy or breastfeeding|| If taking supplements and wanting to monitor effectiveness|| | Advantages:| Easy to use and non-invasive|| Does not require a medical prescription|| Provides quick indications on vitamin D status|| Useful as a preliminary screening before any clinical tests|| | Limitations:| It is a qualitative test, not diagnostic; in case of an abnormal result, a confirmatory laboratory test is recommended|| The result may be influenced by sampling errors, recent intake of supplements, inflammatory status, or renal/hepatic diseases||