Magnesium supports core functions such as energy metabolism, nerve and muscle function, blood glucose control, and blood pressure regulation. It also contributes to bone structure, and a substantial share of body magnesium is stored in bone. In daily practice, magnesium is often discussed when dietary intake is low, during periods of high stress, heavy sweating, certain gastrointestinal conditions, or when medications may affect mineral balance. Still, “everyone needs a supplement” is not evidence-based. A practical first step is improving food sources (nuts, legumes, whole grains, leafy greens). If symptoms persist, a clinician can help decide whether testing, dietary changes, or supplementation is appropriate. Serum magnesium is commonly measured, but it may not perfectly reflect total body stores, so clinical context matters. If supplementation is considered, choose the dose and form carefully and account for kidney function and drug interactions.