Rez...if you still feel sluggish in a few days I'd consider having your blood checked. I felt the exact same way and ended up getting sick and being tested for mono. Was negative on the mono but they said my iron count was low. Seems that being at school and not eating their rotten red meat has lowered my iron counts. Since then ive bought a iron supplement (besides my normal multi) and have had way more energy...Just a thought