What is it used for?A magnesium blood test is used to check to see if you have too little or too much magnesium in the blood. Having too little magnesium, known as hypomagnesemia or magnesium deficiency, is more common than having too much magnesium, which is known as hypermagnesemia.A magnesium blood test is also sometimes included with tests of other electrolytes, such as sodium, calcium, potassium, and chloride.
