48 beats per minute… or just a Mi Band mistake?

I started thinking about another strange thing I had noticed over the last week. According to my Mi Band, each morning after waking up, I would get a notification saying that my heartbeat had gone down to 48 beats. At first, though, I didn't pay much attention to it, as it's just a Mi Band and can be somewhat inaccurate. After all, it's not a real medical device that can measure body parameters correctly.

However, this morning, I didn't get the same notification, which made me curious enough to check and compare the detailed reports. And my latest report actually looked much more ideal, with my heartbeat at 58 beats. When I compared it with the reports from the previous days, they all showed much lower heartbeats, going down to 48 beats. But during the day, everything seemed okay, without any notifications about a low heartbeat.

Looking back now, I have some doubts about whether all those nighttime notifications were actually accurate and whether my Mi Band was showing me real data. At the same time, this might also explain why I had been feeling a bit sick and tired over the last few days. Especially after my outdoor activities, I felt like a sucked lemon and had absolutely no energy left. I didn't even feel like moving. I also had short periods of dizziness and experienced darkening in front of my eyes when I stood up a bit too quickly. And on some mornings, it was really hard to get out of bed.