Diagnosing Hypomagnesemia

A 63-year-old woman with type 2 diabetes was referred for refractory hypomagnesemia (1.4 mg/dL; low normal, 1.8 mg/dL). Her medications included liraglutide, metformin, lisinopril, and magnesium oxide (400 mg twice daily). A recent hemoglobin A1c level was 10.8%, and her urinary magnesium was 117 mg. How do you interpret the urine level, and what would you do next?
Source: JAMA - Category: General Medicine Source Type: research