• Sometimes a bruise develops where the needle was inserted. This is much less likely to happen if you press over the site with cotton wool for several minutes with your arm left straight (not bent).
• As with any wound, an infection may develop where the needle was inserted. See your doctor if the wound site becomes red and inflamed.

Rarely, some people feel faint during a blood test. Tell the person doing the test if you feel faint, as you should immediately lie down to prevent fainting

This depends on the sort of tests you are having done. Many tests can be done on the same sample of blood, so you do not need to have a single bottle for each one: The bottles do not necessarily have to be completely filled either.

• The vein used for blood sampling is usually on the inside of your elbow or the back of your wrist.
• A tight band (tourniquet) is usually placed around your upper arm. This makes the vein fill with blood and makes it easier for the blood sample to be taken.
• The skin over the vein may be cleaned with an antiseptic wipe.
• A needle is then inserted into the vein through the clean skin, causing a sharp pricking sensation. The needle is connected either to a syringe, or directly to blood sample bottles.
• The tourniquet is undone. When the required amount of blood is taken, the needle is removed. The small wound is pressed on with cotton wool for a few minutes to stop the bleeding and prevent bruising. A sticking plaster may be put on. The blood is placed in bottles. There may be a slight ache following a blood test.