After inserting the needle I heard it's good to pull back the syringe checking to make sure blood doesn't get drawn up into the syringe. I tried this and noticed it's very hard to pull back the syringe. I'm assuming, if I hit a vein, I would be able to pull back the syringe easily and blood would get drawn up quickly. Is this assumption correct?
In addition, sometimes when I pull back the syringe it creates an air bubble in the syringe. Once I let the syringe go it forces the air back into my body. Could this create a problem? (When intially drawing my syringes I am always 100% sure not to have air bubbles in my syringe.)