question: How long does it take a dose of atenolol to have an effect on BP?  My MD says that my elevated am is from anxiety and that I do not have high BP.  I need to get my BP down in order to do pulmonary rehab.  I was fine for 19 visits but turned away yesterday.  I am to take 1/2 mg. atenolol.  I am 74, 128 lbs, 5'5"