Intravenous (IV) cannula

An intravenous (IV) cannula is a very small, flexible tube which is placed into one of your veins, usually in the back of your hand or in your arm.

One end sits inside your vein and the other end has a small valve that looks a bit like a tap. We use a cannula if we need to put medicines or fluids straight into your bloodstream. It can sometimes be used to take blood samples during tests and investigations. 

Why do I need an IV cannula?

You need an IV cannula if the medication or fluids you are being given need to go straight into your bloodstream. The nurse or the doctor will explain why you need the IV cannula. 

Some drugs are given over a period of a few minutes, which we call a bolus or push. Other medications are given over several hours using a special pump. We often call this an infusion or drip. 

What happens

Having a cannula put in is very similar to having a blood test. The nurse or doctor will examine your hands and arms to find the best place to put the cannula. Remember to tell them if you have a preference for where it goes. They might put a tourniquet (a stretchy band) around your arm as this helps to make your veins easier to see. 

When they have chosen a suitable position you will be offered a choice of anaesthetic cream to put around the area to numb it (this takes 45 minutes) or topical cold spray just before the procedure. You don’t have to have either of these – lots of people choose to go without.


If you can stay relaxed and still it will be much quicker and easier for the doctor or nurse and less likely to be painful for you. Try to sit in a comfortable position and rest your arm on something.

Some people like to distract themselves from what is happening. You could listen to music, or talk to the staff, or watch TV. 

If you are scared of needles, let your nurse or doctor know so that they arrange to have a play specialist to support you. It should take only a few minutes to put an IV cannula in. 

Having a cannula put in

The doctor or nurse will wipe off the anaesthetic cream if you had it. A needle is then inserted through your skin into one of your veins. The needle is removed, leaving just a tiny, thin, flexible tube inside your vein. The IV cannula is safely taped into place with a clear plaster. A bandage is usually put over it. This will keep it clean and prevent the IV cannula getting knocked. Your nurse will talk to you about keeping your cannula dry while you wash. 

The IV cannula should not hurt when it is in place, and can be left in place for several days. It will need to be checked daily for any signs of redness, pain or swelling. You should tell your nurse if it does hurt or if you are worried.

Having a cannula removed

It will take only a few seconds to remove your IV cannula. 

Your nurse will remove the bandage and loosen the clear plaster. Some clean gauze will be pressed onto your skin as they remove the thin flexible tube. They will need to press for a few minutes to prevent bleeding. Some people do bleed a little bit afterwards, but this will stop very quickly. You may also be left with a small bruise – this should heal as normal. Your nurse will put a plaster over the area to keep it clean. This can be removed after a short time.

Compiled by: 
Great Ormond Street Hospital
Last review date: 
March 2014


This information does not constitute health or medical advice and will not necessarily reflect treatment at other hospitals. If you have any questions, please ask your doctor. No liability can be taken as a result of using this information.