<unk>  is not easy to directly measure. Typically the diagnosis is based on finding low blood<unk>  levels (hypomagnesemia). Specifically by finding a plasma<unk>  concentration of less than 0.6 mmol/l (1.46 mg/dl). Severe disease generally has a level of less than 0.50 mmol/l (1.25 mg/dl).<unk>  (or depletion) refers to low total body levels of<unk>  which is usually determined by finding low blood levels (hypomagnesemia). Hypomagnesemia refers only to blood levels of<unk> . Either of<unk>  and hypomagnesemia can be present without the other. Electrocardiogram The electrocardiogram (ECG) change may show a tachycardia with a prolonged QT interval. Other changes may include prolonged PR interval, ST segment depression, flipped T waves, and long QRS duration.
Magnesium deficiency
Fluorine deficiency
Boron deficiency 
Fluoride toxicity
Selenium deficiency
Thiamine deficiency
Copper deficiency
Vitamin D toxicity