Hypomagnesemia from malabsorption and renal magnesium wasting treated with high-dose magnesium glycinate: A case...

Hypomagnesemia is common after Roux-en-Y gastric bypass (RYGB) due to reduced gastrointestinal absorption; however, management becomes particularly challenging when renal magnesium wasting coexists.

This report describes refractory hypomagnesemia in a post-RYGB patient with confirmed renal magnesium wasting and evaluates the role of magnesium glycinate as an alternative oral replacement strategy to oral magnesium oxide and intravenous magnesium sulfate.

A 56-year-old female with a history of RYGB and chronic malnutrition presented with bilateral lower-extremity weakness and neuropathic symptoms. Despite high-dose intravenous magnesium sulfate administered via total parenteral nutrition and intravenous supplementation, as well as oral magnesium oxide, serum magnesium levels remained persistently low (1.1-1.9 mg/dL) with only transient correction. A markedly elevated random urine magnesium level confirmed renal magnesium wasting as a contributing factor. Oral therapy was transitioned to magnesium glycinate, a chelated formulation with alternative absorption pathways. Following this change, serum magnesium improved to 2.0-2.1 mg/dL without further need for intravenous supplementation, and episodes of severe hypomagnesemia decreased.

This case highlights the importance of evaluating both gastrointestinal malabsorption and renal losses when hypomagnesemia remains refractory to standard therapy in post-bariatric surgery patients. Magnesium glycinate may represent an effective long-term oral replacement option in patients with combined malabsorption and renal magnesium wasting. Further research is needed to guide formulation selection in this population.