Why do doctors put the needle through a bottles lid to extract its contents

Whenever I've seen doctors (or other medical professionals) draw something up into a syringe (vaccine, anesthetic etc.) they always put the needle through the lid of the bottle. Why do they do this? It would just make the needle more blunt and leave the bottle with a hole in its lid where its contents could drain out.

The top of the bottle is sealed with a thin membrane of rubber. This keeps the contents clean and free from bacteria. When the needle is inserted into the bottle, you push it through the rubber. The point of the needle is incredibly thin and sharp - so the hole in the rubber is microscopically tiny. As the needle goes further into the bottle, it pushes the hole a little bigger because the needle is slightly larger below the tip.

When you've sucked up the desired amount of the drug, you remove the needle - the remaining hole is very tiny because it was made by the tiny tip of the needle. Also, the rubber tends to close over, after the needle is removed.

Try this yourself - stick a pin into a bit of rubber that you've stretched over the top of a bottle. You'll see how the hole seals itself after the pin is removed.

Having said this, you should know that bottles of drugs are only used once and then discarded. No cross-contamination is possible.

The bottles that are sealed are pretty much bacteria free. Doctors need the bottles so they can keep liquid in something that is bacteria free.

The lid is probably made a lot less thicker so the needle can get the liquid and the smallest(that they can possibly have) amount of bacteria gets into the needle

How else would they store stuff if not with bottles?

"Whenever ...doctors ...draw something up into a syringe ...they always put the needle through the lid of the bottle. Why do they do this?"


Because it is a lot harder to put the needle through the glass vial.

Inserting the needle through the covering lessens the chance of introducing any micro-organisms etc into the fluid as it's being drawn into the syringe. The contents of the bottle aren't reused.

I think its so that no bacteria would contaminate the liquid. I mean it is safer and since they draw it through a syringe directly, its practically air tight.

I think it's so the inside of the bottle doesn't get bacteria inside of it.

It's RUBBER-won't "blunt" steel
Puncture SEALS-it's rubber.
Tiny puncture SEALS-it's rubber.