Hypermagnesemia is when the serum magnesium concentration exceeds the normal value. It refers to the situation where the blood [Mg2]>1.05mmoL/L or more. Except for a few iatrogenic factors that lead to excessive magnesium entering the body, most of them are caused by reduced excretion due to renal dysfunction. Like hypomagnesemia, serum magnesium concentration is not a reliable indicator of increased magnesium, because 25% of magnesium in serum is bound to protein, and this part of magnesium does not play a physiological effect; magnesium ions are mainly in cells, so when the body's magnesium content increases, serum magnesium can be within the normal range. But in general, hypermagnesemia and increased magnesium in the body are consistent. Just as the kidney has a certain delay in regulating sodium ions, potassium ions, and bicarbonate ions, the kidney's regulation of magnesium does not play a significant role quickly. Therefore, if a large amount of intravenous magnesium preparations are used without attention to monitoring, severe hypermagnesemia may also occur. If combined with renal dysfunction, the regulatory function of the kidney is severely weakened, hypermagnesemia is likely to occur.