magnesium supps/low b.p.

I have extremely low b.p and tachycardia. I am already taking magnesium (glycinate) . I know that it is good for the heart and reduce palps. However, people also take it to lower their blood pressure. Does anyone know if increasing my Mg (I am only taking 250 mg) will DECREASE my already low blood pressure or will it (potentially...) just help to normalize it. My goal is to increase my b.p and decrease the tachycardia (which I think is happening as a result of the low b.p...) (Of course all of it is related to my screwed up autonomic nervous system and adrenals...)

Tks!