Ionized magnesium (iMg) vs. total magnesium (tMg) – Are they equal?

Magnesium (Mg) abnormalities, in particular hypomagnesemia, can have serious clinical manifestations. Ionized magnesium is the biologically active and the more clinically important form of magnesium.^1-6

Two clinical situations highlight the importance of knowing ionized magnesium (iMg) instead of the total magnesium (tMg).

• The use of calcium chelators such as citrate, which also chelates magnesium, will cause a lower result when measuring biologically active iMg. Hutten et. al. found that patients receiving CRRT with citrate anticoagulation had normal tMg levels, but low iMg levels.⁷
• In a study done in Surgical ICU patients at Massachusetts General Hospital, 21% of tMg tests which were reported as normal were hypermagnesemic based on iMg exposing patients to potential risks associated with elevated Mg levels. ⁸

A new document from Nova Biomedical provides the commonly accepted reference ranges for the biologically active ionized magnesium levels in adults and pediatrics and compares those ranges to total magnesium levels: iMg and tMg comparison

Nova Biomedical's Prime Plus blood gas analyzer can be used to measure iMg. For more information about Nova Biomedical's Prime Plus, head to the product site through links below or contact us.

• Nova Biomedical Prime Plus (Finland)
• Nova Biomedical Prime Plus (Sweden)
• Nova Biomedical Prime Plus (Norway)
• Nova Biomedical Prime Plus (Denmark)

Aidian is the proud distributor of Nova Biomedical's blood gas analyzers in the Nordics.

References

1. Jiang et al. Shock 2017;47(3):288-295.
2. Escuela et al. Intensive Care Med 2005;31(1):151-156.
3. Wilkes et al. Anesth and Analg 2002;95(4):828-834.
4. Soliman et al. Crit Care Med 2003;31(4):1082-1087.
5. Yeh et al. J Crit Care 2017;42:147-151.
6. Huijgen et al. Am J Clin Pathol 2000;114:688-695.
7. Hutten et al. Ionized and not total magnesium as a discriminating biomarker for hypomagnesaemia in continuous venovenous haemofiltration patients. Nephrol Dial Transplant, 2021.
8. Yeh et al. Total and ionized magnesium testing in the surgical intensive care unit - Opportunities for improved laboratory and pharmacy utilization.