Is it safe to take magnesium oxide every day?

Yes with supervision: If you have somewhat slower kidney function you could accumulate magnesium levels in blood causing abnormal heart rhythm. Need a doctor supervision for every day use for long term. At least need doctors clearance for starting a long term use. He will factor the risk vs benefit and your blood level and your other meds interacting with it and the cause to use it and if there is a better option.