How do doctors fill up syringes?

Answer 1

It depends what substance is going into the syringe. If it is a medication, sometimes the doctor will attach a hollow needle to the syringe and place the needle into a bottle of medication - this way he can draw up the medication into the syringe via the needle. The needle will then be removed from the syringe and discarded.

The alternative method is that some bottles have a silicone stopper around the top, with a tiny hole in the middle where the (needle-less) syringe fits. You stick the tip of the syringe into hole so that it fits snugly, turn the bottle upside down and draw up the medication. The snug fit means that the medication doesn't drip everywhere when you turn the bottle upside down.