Magnesium is a vital "master mineral" for your body. It is essential for over 300 processes, including muscle relaxation, nerve function, energy production, and maintaining a steady heartbeat. Low levels can lead to muscle cramps, fatigue, and weakness. This test measures the magnesium level in your blood, providing a critical insight into your body's "spark plugs." This simple blood test is a key part of investigating unexplained fatigue or muscle issues. Get the data you need to restore your energy.