Hi @ellamster,

Magnesium is one of the more abundant minerals in the body, which reflects its importance. Studies have shown that your pulse/heart rate is impacted by the amount of magnesium in your body, and deficiency can result in arrhythmias. It plays a role in hundreds of chemical reactions, many of them having to do with changing food into energy. https://www.mayoclinic.org/drugs-supplements/magnesium-supplement-oral-route-parenteral-route/description/drg-20070730

However, as @hopeful33250 mentioned, you are taking a rather high dose. The recommended daily allowance of magnesium for adults is 320 mg for women and 420 mg for men. The upper intake level from supplements is 350 mg per day, and excess intake of supplemental magnesium may result in toxicity with symptoms like lethargy, confusion, abnormal cardiac rhythm, muscle weakness.

Here’s a fact sheet from the NIH (National Institutes of Health) which notes:
"Very large doses of magnesium-containing laxatives and antacids (typically providing more than 5,000 mg/day magnesium) have been associated with magnesium toxicity. Symptoms of magnesium toxicity, which usually develop after serum concentrations exceed 1.74–2.61 mmol/L, can include hypotension, nausea, vomiting, facial flushing, retention of urine, ileus, depression, and lethargy before progressing to muscle weakness, difficulty breathing, extreme hypotension, irregular heartbeat, and cardiac arrest. The risk of magnesium toxicity increases with impaired renal function or kidney failure because the ability to remove excess magnesium is reduced or lost.” https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/#h8

I’m tagging @personalhell @sue225 @irenec @tiss as they may be able to share their experiences with you.