It would depend on the substance, and How much of it.

Bro obviously you are fine you would be in touble right away you didnt hit a vein i have had it happen b4....you learned a lesson is all..use smaller needles and always asperate.....You are fine.....

hi talon , yeah i know im fine , just wondered what would happen ...
just ordered sum smaller needles .. wait till i go back into that health clinic !! lol

ya ok well many things can happen if you inject into a vein mainy heart attack and or stroke..remember it is an oil so oil and blood dont mix it will fuck you up bro...