Always always always, at least for me.
I got lazy on a cycle I was using liquid A-50 (oxsomethingorrather)and did not. Put 1 1/2 cc in a vein. I never felt such pain before. My skin was on fire in 10 seconds, every pore hurt. Then I the ringing in my ears made me deaft. I went to bathroom and shut the door, so my girlfriend would not see me and freak. Then the room "went white", and I could not see. This was followed by total loss of breath, no air for a good 30 seconds. I was sure I had just killed myself, and could not even call for help. After I got my breath back all of the problems slowly went away. I felt like shit for the rest of the day, and missed the my lift. And I became a bit afraid of liquid A-50. The rest of the cycle I took it orally.
Take my word for it. Never skip this step.