Magnesium is an essential mineral that plays a vital role in over 300 enzymatic reactions in the body, including muscle and nerve function, heart rhythm, bone health, and energy production. This test measures the amount of magnesium in the blood and is used to evaluate magnesium status, which can affect multiple body systems. Low magnesium levels (hypomagnesemia) can cause muscle weakness, tremors, irregular heart rhythms, and seizures. High magnesium levels (hypermagnesemia) are less common but can occur in kidney failure or with excessive magnesium supplementation. Magnesium deficiency is often associated with other electrolyte imbalances and can be caused by poor dietary intake, alcoholism, diabetes, certain medications, or malabsorption disorders. This test is commonly ordered when evaluating unexplained muscle symptoms, heart rhythm problems, or as part of comprehensive metabolic panels.