GNC Magnesium 250mg is a magnesium citrate supplement designed to support your bones and teeth. Magnesium citrate is a highly absorbable form of this essential mineral. Magnesium has several other critical functions in your body besides supporting your bone and teeth. Your nerves, heart and skeletal muscles all need magnesium to function. Magnesium is important for proper vitamin D function and is required for energy production. Your body also uses magnesium to synthesize DNA and RNA. Chewable magnesium supplements are a convenient alternative to tablets.