The original instructions called for twice a day; so I've been following that. It is recognized that taking it on an empty stomach helps it to be more bio-available. I normally take my first dose the very first thing in the morning, before brushing teeth, showering and shaving. Then I don't eat anything for more than an hour. My second dose is about 10:30 PM. I will have stopped eating anything about 6:30.
It has never made me tired as the documentations suggest. I wish it would for the evening dose.