I am taking Atenolol 100mg, Lifezar 50 (losartan), and aspirin 75 for nearly a year now and have never missed a dose, but today what should not happened had happened. I am always taking my medicines at 6:00 in the morning, but today I took them at about 6:30 in the afternoon or more than 12 hours late. I started to suspect that I might have missed my dose when I felt some sort of headache, and it proved to be true when I count my medicines which are kept in the envelopes mark with the name of the months. I therefore immediately took the missing dose and my headache disappeared after about 30 minutes, and I am ok now, no headache whatsoever. My question is:- Is the headache the result of missing my dose or does it signifies something else?