Customs leaving the US usually not bad.
Take only what shots you will take while there with you in one vial. Place it in you toiletries(carryon), in a side pouch or in travel bag with the other crap. Leave the needle is best, but you could gamble with one, I have done it and it made it through carryon xrays.
Go thru customs. Its not illegal, if you get a random search say what it is, dont lie about it and youll be fine. 2cc's in a vila looks like b-12
They are looking for bombs and huge quantities of street drugs.
Plus coming back to US is where its tricky, but you will throw that out once used on trip.
Done this to mexico, canada, europe.
Assuming you aren't going to Saudi Arabia or Thailand where you might end up on Locked Up Abroad for 2cc of test E...HA
Its a gamble, worst case you lose your shot... Buying juice in a foreign country sounds less appealing.
Anything small pills/vials/ in plain sight in your travel bag shouldnt be a prob.. Customs says if medications aren't in their original container have a copy of presript. But they have never checked.
I wouldnt hide in the checked luggage because the customs agent will think its heroin if you have it wrapped in your shoe in checked bagged and your bag gets randomed..
Id probably leave the needle and buy one there - depending on where you are going.
Good luck.