I am not a doctor but as a patient with a lot of experience with beta blocker medication, including the one you are taking, I can say I consider 50 mg a day to be a moderate level does, but if it causes very low heart rate, I consider anything under 50 to be very low, and some dizziness the lower dose seems to be a good change,
Given you seem to be moving toward a more normal heart rate and I didn't see any mention of problems from the reduced dose it seems to me you may have found the correct dose level for you.
What are you taking the BB for? If you don't have an irregular HR, too high a HR (not your problem) or high blood pressure I have no idea why you are even taking a beta blocker.
Thank you very much Jerry for you kind advice. I take half tablet of BB now and feel fine. The reason for me to take BB because I have Hypertrophic cardiomyopathy. BB is the first line medication.
BTW, I tried to post a question to heart disease doctor forum. But that page is always "busy".
I have the same thoughts as Jerry_NJ, but it's never a bad idea to run it by your own doc.
Thank you for the complement, my many typos can cause problems especially for anyone speaking English as a second language. You write in English as well or better than many native English speakers - myself included. Well I just assume you are not native English a speaker as you are in China, but that is only an assumption.
There is a "Heart Disease" Community that gets more MD attention than the Heart Rhythm - the Doctor's forum may not have one or more MDs willing to participate, I'll take a look.
My response above was under the belief I was on the Heart Rhythm Community, but no matter. I checked both the Heart Disease and Heart Rhythm listed on the "Doctor Forums" and both reverted to the volunteer Communities of the same names.