Also, make sure you measure it correctly. Don't just pull the solution into the syringe until you hit 0.5 ml and expect that to be 0.5ml. You'd have to account for the solution in the tip of the syringe and needle. In this case the difference would be significant enough to try to make it as accurate as possible in my opinion.
You're better off pulling the solution into the syringe with some air, turn the syringe upside down, and pull the stopper to line it up with any whole number. For example, if you pulled the plunger to the 2ml mark, with the syringe upside down, if the top of the solution lines up with 1.5ml, that means you've got exactly 0.5ml in the syringe and are good to go.
I also like to leave a tiny bit of air in the syringe for the inject. Let the air bubble float to the back of the syringe, and as long as you inject with the syringe vertical (perpendicular to the ground) with the needle end down, the air bubble will help push that last bit of fluid out of the syringe. If the air bubble is about the right size, little to none of it will exit the syringe and even if a little bit of air gets injected it's really nothing to worry about, especially with a subcutaneous injection. It's been a while since I injected but with a standard 3ml syringe I think I used something like 0.5ml of air.
