“Avoid” is often better framed as “use caution.” The highest-risk group is people with impaired kidney function, because magnesium is cleared by the kidneys and can accumulate. Those prone to diarrhea (e.g., IBS-D) may not tolerate higher doses. People taking certain medications (some antibiotics, thyroid drugs, bisphosphonates, etc.) should separate magnesium by a few hours to avoid absorption problems. Individuals with cardiac rhythm issues, multiple chronic conditions, or polypharmacy should avoid random self-supplementation and follow a clinician-guided plan. During pregnancy and breastfeeding, needs and safety should be individualized.