Dear Madam
Thanks for your query to HCmagic.
Usual dose of magnesium oxide as a supplement is ~800 mg / day.
Intake of magnesium oxide in the dose of 1000 mg per day may be associated with side effects. (Not 100% of subjects will have it; but yes you can have side effects because of high magnesium levels as well as because of usual dose side effects of magnesium oxide). Commonly described side effects associated with this salt are diarrhea/ vomiting / dyspepsia. There can be serious side effects on nervous system and heart , but are less likely at this dose, unless taken for long term.
Any supplement should be taken only when it is clearly indicated. Once your magnesium levels are normal, you must discuss it with your doctors and stop it accordingly.
Feel free to discuss further.
Sincerely
Sukhvinder XXXXXXX