99% of doctors, gurus, trainers, health nuts ect... always push taking high doses of Vitamin D. What they don't understand is Vitamin D is something you should avoid taking. Vitamin D shuts off your immune system. Whoops. That's not a good idea. Why low vitamin D on a lab doesn’t always equal deficiency - you don't need Vit D as you might assume. A low 25-hydroxy vitamin D result often reflects inflammation, not lack of intake. - Storage D: 25-hydroxy vitamin D (what most doctors order) - Active D: 1,25-dihydroxy vitamin D (rarely tested) A high active D with low storage D often signals infection or immune activation, not deficiency. High-dose vitamin D can create new problems. When taken without cofactors, vitamin D can: - Deplete magnesium (required at multiple steps of vitamin D metabolism) - Suppress vitamin A (retinol) uptake - Disrupt potassium and sodium balance - Worsen fatigue, anxiety, sleep issues, and hormone symptoms in some people Vitamin D is essential but high-dose supplementation without minerals, vitamin A, and context can backfire. Low vitamin D is often a marker of inflammation, not a mandate to supplement more. Low vitamin D is correlated with high inflammation, which is actually driven by iron accumulation. Taking vitamin D3 supplements can exacerbate this problem Humans have more than a dozen different forms (metabolites) of 25D and the typical vitamin D test works on two of them. RENAL POTASSIUM-WASTING INDUCED BY VITAMIN D https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3765911/ https://www.ncbi.nlm.nih.gov/pubmed/25048990