2 days ago my husband was in ER. His blood pressure was very low, 73/45 ,78/37 and such. When it rose into the 90 s/ 57 ish, they released him because he wouldn t be admitted. Today, after monitoring his BP every hour or so, it ranged from 98/56 to 165/89. He doesn t feel bad but does feel tired and weak and if he does any physical activity he said he feels like his heart is racing. Other than dehydration, flu was ruled out, is there anything else this might be or is there anything I need to be more watchful for?