This blood test seeks the Magnesium level, a low level of which can cause fatigue, muscle weakness, cramps, muscle spasms or even convulsions. As magnesium is found primarily inside cells, measurement of the whole blood level (as opposed to serum) gives a more accurate insight into the total level in the body.

Magnesium is the second most common mineral found inside cells, second only to potassium. It is key to more than 300 reactions in our bodies. A red cell (whole blood) magnesium test should be considered when a patient is suspected of having a lack - particularly seen in malnutrition, alcoholism, and diarrhoea amongst others. Dietary deficiency is surprisingly common though even in the western world - so if reduced intake is suspected this is a test worth considering.