Hi. I am a 36 yo fit female who had DVT 10 years ago. I recently had another DVT scare with a d-dimler positive result but the scans were negative. As a precaution I have been told to take clexane 40mg prior to any flights. My DR has said it should be 6 hours before the flights. I have over 24 hours long haul flying coming up and due to a short domestic flight can take the clexane either 8 hours or 3 hours prior to the first long haul flight. Which would be better?