While using Rogaine, my heart seems to beat faster off and on. Do I have anything to worry about?

This can sometimes be a side effect. I recommend getting a formal evaluation with a hair loss expert to go over your condition and advise you on best treatment options. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

This is a side effect from minoxidil. Minoxidil can (in a small proportion of users) lower blood pressure and in turn the body increases heart rate to compensate. You are correct that your heart rate goes up when you exercise, but your blood pressure goes up too. It's a very different physiology when one compares exercise effects on the heart to minoxidil effects on the heart. A person's heart rate also goes up (and blood pressure goes down) when they are dehydrated and we know this is not good.  A person's heart rate can go up (and blood pressure go down) with topical minoxidil. This does not happen to everyone. But if there are significant heart rate changes with minoxidil, I advise checking with one's physician about whether or not to stop. This is especially important for those over 65.