Koch et al studied total and ionized magnesium levels in patients in the intensive care unit (ICU). They determined that the ionized magnesium could be estimated based on the total magnesium serum level. The authors are from the University of Texas in Houston.

ionized magnesium in mmol/L =

= (0.66 * (total magnesium in mmol/L)) + 0.039


This can be reversed to estimate the total magnesium if the ionized level is known:


total magnesium in mmol/L =

= ((ionized magnesium in mmol/L) - 0.039) / 0.66 =

= (1.515 * (ionized magnesium)) - 0.059



• The authors tested the relationship over a range near the normal range (total magnesium from 0.57 to 1.08 mmol/L). Whether the relationship exists at very low or high values is undetermined.

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