Depending how long you’re away for, test D could be a better choice as test U is a super long ester, so it will release slowly too. If you’re doing a big dose before heading off it may take longer than expected to pick up.
I’m going away mid year for 2 weeks and thinking I’ll switch to test D a few weeks prior so that it’s at peak levels when I leave and do my dose with a touch more to hopefully be at a decent level by the time I get home.