What are serious magnesium metabolism disorders and how they can be diagnosed? it seems like my body is not absorbing enough or excreting too much

Low magnesium: Low magnesium can be caused by: Alcoholism, Chronic diarrhea, intestinal diseases: celiac and inflammatory bowel dz, diet deficiency, meds: Diuretics, Prevacid (lansoprazole) and like acid inhibitors, chemotherapy, and certain antibiotics. Genetic defects of kidney tubules can cause low mag (Gitelmans), and excess aldosterone secretion by adrenals. Eval: 24 hour urine Mag, Ca, Sodium, Potassium excretion