Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. The primary aim of Bisoprolol is not to reduce blood pressure but to control increased heart rate, commonly the issue with A-fib. So to decide whether to cut down on it first heart rate should be studied, you make no mention of that. Also other causes for the lack of energy should be considered like anemia, metabolic alterations or low thyroid function for which some routine blood tests should be done. If at the end no other cause is found and your heart rate is well controlled then it may be considered to reduce Bisoprolol dose. Hope I have answered your query. Let me know if I can assist you further.