What is magnesium deficiency in cells symptoms? and what cause a person to have normal levels of magnesium in blood test but not enough in cells?

Unfortunately measurements of extracellular magnesium aren't an accurate assessment of the status of magnesium in cells and body tissues. Intracellular magnesium measuring is possible but not routinely done. Cardiologists,& neurologists have been aware of the disconnect between cellular and extracellular magnesium because of their interests in cardiac arrhythmias and neuromuscular symptoms.