To understand humans' requirements for magnesium and the effect of magnesium on health, it is important to identify sensitive and population-specific biomarkers of magnesium status. Thus, we assessed the effectiveness of different magnesium status biomarkers through a systematic review of published magnesium supplementation and depletion trials in healthy humans. The methods used in this study included a structured search on Ovid MEDLINE, EMBASE (Ovid) and Cochrane databases up to September 2008, followed by the use of formal inclusion/exclusion criteria, data extraction, validity assessment, and meta-analysis. A total of 20 potential biomarkers of magnesium status were assessed from 21 included publications. The majority of studies included were magnesium supplementation studies. Fewer magnesium depletion studies were identified. Available data analysis suggests that serum/plasma magnesium concentration, red blood cell (RBC) concentration and urinary magnesium excretion responded to dietary manipulation. For other biomarkers with available data, it was not possible to draw any conclusions about their usefulness as magnesium status biomarkers. The lack of data prevented detailed subgroup analysis. In conclusion, although limited data were available, serum/plasma magnesium concentration, RBC magnesium concentration and urinary magnesium excretion appear to be useful biomarkers of magnesium status in the general population. Further high-quality studies are needed to assess the effectiveness of existing and newly developed biomarkers, especially in populations that are vulnerable to magnesium deficiency.