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Updated: Aug 8, 2026

Measurement of Extracellular Ion Fluxes Using the Ion-selective Self-referencing Microelectrode Technique
09:18

Measurement of Extracellular Ion Fluxes Using the Ion-selective Self-referencing Microelectrode Technique

Published on: May 3, 2015

Variability within individuals of plasma ionic magnesium concentrations

Ian J Newhouse1, Kris P Johnson, William J Montelpare

  • 1School of Kinesiology, Lakehead University, Thunder Bay, Ontario, Canada. Ian.Newhouse@Lakeheadu.ca

BMC Physiology
|April 30, 2002
PubMed

Insights

Ionic magnesium (iMg) levels show significant within-day variability, suggesting a potential circadian rhythm. Clinicians should interpret single iMg measurements cautiously due to this biological fluctuation.

Area of Science:

  • Clinical Chemistry
  • Biomarkers
  • Physiology

Background:

  • Ionic magnesium (iMg) is the biologically active form, commonly measured using ion-selective electrodes (ISE).
  • Existing evidence suggests substantial within-subject variability in iMg levels.

Purpose of the Study:

  • To investigate the extent and patterns of within-subject variability in ionic magnesium (iMg) measurements.
  • To determine if iMg exhibits significant diurnal or between-day fluctuations.

Main Methods:

  • Analysis of individual iMg ranges and coefficients of variation (CV).
  • Comparison of biological variability to analytical variation.
  • Assessment of within-day and between-day iMg variations using statistical analysis.

Main Results:

  • Biological variability accounted for nearly half of the total iMg variation (mean CV 4% vs. analytical variation 2.3%).
  • Significant within-day iMg variations were observed between 7:00-10:00 and 10:00-22:00 (p <.001).
  • No significant between-day variations in iMg levels were detected (p =.56).

Conclusions:

  • The observed within-day variability suggests a potential circadian rhythm for iMg.
  • Single iMg measurements require cautious interpretation pending further research into iMg variability.
Abstract

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