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. 2020 Jan 20;12(1):263. doi: 10.3390/nu12010263

Table 3.

Mean ionized magnesium concentrations in fresh, refrigerated and frozen blood samples and mean difference from baseline (fresh) after refrigeration and freezing, n = 39.

Time from Draw to Analysis 1 pH 1 Concentrations, 1 mmol/L Mean Difference (95% CI), mmol/L Percentiles of Difference from
Fresh iMg, mmol/L 2
Min 25th 50th 75th Max
iMg (normalized)
Fresh 3 4.8 min (3.4) 7.38 (0.03) 0.54 (0.05) Reference - - - - -
Refrigerated 69.6 min (25.3) 7.45 (0.04) 0.68 (0.04) 0.14 (0.12,0.16) 0.07 0.10 0.13 0.17 0.31
Frozen 82.2 days (15.4) 7.51 (0.04) 0.73 (0.05) 0.19 (0.18,0.21) 0.11 0.15 0.19 0.25 0.29
iMg (not normalized)
Fresh 4.8 min (3.4) 7.38 (0.03) 0.54 (0.05) Reference - - - - -
Refrigerated 69.6 min (25.3) 7.45 (0.04) 0.65 (0.04) 0.11 (0.10,0.13) 0.04 0.07 0.09 0.13 0.25
Frozen 82.2 days (15.4) 7.51 (0.04) 0.68 (0.05) 0.14 (0.12,0.15) 0.05 0.09 0.13 0.18 0.20

1 Mean (standard deviation); 2 the distribution (in percentiles) of the difference between refrigerated vs. fresh and frozen vs. fresh. A value of 0 indicates that the iMg measured in refrigerated (or frozen) and fresh were identical. 3 Refrigerated and frozen blood samples were measured in serum, while fresh was measured in whole blood.