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Objective: To determine if an association between ionized magnesium (iMg) and total magnesium (tMg) exists in healthy and hospitalized dogs admitted through an emergency service and to assess the associations between iMg and tMg with total protein, albumin, ionized calcium, and total calcium. Design: Prospective cohort study. Setting: Veterinary teaching hospital. Animals: Sixty‐nine dogs were enrolled. The healthy control group (group 1) included 24 dogs, and the hospitalized group (group 2) included 45 dogs. Interventions: None. Measurements and Main Results: For both groups, signalment, a venous blood gas, and serum biochemistry were obtained. In addition, the presumptive diagnosis was recorded for group 2. Blood was obtained prior to any therapeutic interventions. Group 1 tMg was within the reference interval (RI), and the values for iMg were used to provide a healthy group range (HGR) of 0.44–0.50 mmol/L. Group 2 tMg was within the RI, but iMg was below the calculated HGR range (group 2 median iMg = 0.4 mmol/L; range = 0.27–0.70). There was a significant positive correlation between iMg and tMg in each group (group 1: r = 0.6713, P = 0.0003; group 2: r = 0.5312, P = 0.0002). Ionized Mg and tMg were not significantly associated with any of the other evaluated variables in either group. Conclusions: Ionized Mg and tMg were significantly associated in both healthy and hospitalized dogs, but the relationship was weaker in the hospitalized dogs compared with the healthy population. For hospitalized dogs, the relationship was weak enough to question the validity of using iMg and tMg interchangeably to track magnesium status. [ABSTRACT FROM AUTHOR]

Background: The relationship between the development of SHPT and ionized magnesium (iMg) concentrations in blood of dogs with chronic gastrointestinal (GI) disease and abnormally low 25(OH)D is undefined. Objectives: Evaluate relationships between ionized magnesium (iMg), PTH, ionized calcium (iCa), and 25(OH)D in dogs with chronic enteropathy (CE) with or without protein‐losing enteropathy (PLE) and abnormal 25(OH)D. Determine whether dogs with CE or PLE, decreased 25(OH)D and SHPT have differences in iMg, iCa, or 25(OH)D when compared to dogs that do not have SHPT. Animals: Fifty dogs with CE +/− PLE and abnormally low serum 25(OH)D. Methods: Retrospective search of submissions database at a veterinary diagnostic laboratory for vitamin D profiles submitted in years 2017 to 2020. Cases were excluded if supplemented with Ca, Mg, or vitamin D. Spearman correlation was performed to evaluate relationships between iMg, PTH, 25(OH)D, and iCa. Ionized Mg, iCa, and 25(OH)D concentrations were compared between dogs with SHPT and those with normal PTH concentrations. Results: Concentrations of iMg were weakly negatively correlated with PTH (rho, −.31; P =.03), and weakly positively correlated with serum 25(OH)D (rho,.34, P =.02) and iCa (rho,.42, P =.003). Ionized magnesium concentrations were lower in dogs with abnormally low 25(OH)D and SHPT compared to dogs with abnormally low 25(OH)D and normal parathyroid hormone concentrations (P =.01). Conclusions and Clinical Importance: Hypomagnesemia might contribute to alterations in iCa and parathyroid hormone in dogs with CE +/− PLE and abnormally low 25(OH)D. [ABSTRACT FROM AUTHOR]