I am a 24-year-old male and have been on Propecia for roughly two and a half years. I take it every day as soon as I wake up, but on weekends when I sleep in I find myself taking it two hours or so later than usual. Does this significantly impact its effectiveness?
No, it does not. We measure Propecia both in the blood stream (a half life of 4-6 hours is thought to be the standard) and in tissue fixed areas (we believe that this remains in the tissues up to a week after ingesting the drug). Slight variations in daily intake timing will not impact the efficacy of the drug.