Is it possible for my heart rate to be 255 beats per minute?

Your HR monitor may have simply malfunctioned. Assuming it didn’t 255 b/m is dangerously high. I’m not worried about your heart being damaged but your heart beating that fast is probably not on a normal rhythm. You should see your doctor who will probably order an EKG and stress test. They need to figure out what is going on with your ticker. You can literally drop dead from heart arrhythmia. This is not something you should ignore and hope gets better on its own.

I think it might be the HR monitor. Will in any case rest for this week, and then take it easy, and monitor it, if it goes above 200 again, i will stop and phone a friend to take me to the doctor.

I think if it really was going that fast, you would feel it and not be able to function correctly. It may be the monitor, but i’d see a cardiologist to make sure. Heart problems are sometimes there without notice. I found out i had a heart problem from getting pnuemonia multiple times within a 6 month period. (that sucked so much) And they did an ECHO on my heart. I never even had symptoms. So you should see a doctor if it happens again. Take it easy for awhile.

Thanks, will definitely take it easy, planning to do a short run tomorrow, just to see if anything abnormal happens.

Sounds good! Be careful. :)