Blood draw
Your blood can tell researchers a lot about you. Depending on which study you're enrolled in, we may need to get some blood from you. We will collect the blood sample from a blood vessel in your arm.
During the draw
The arm is a convenient part of the body to use because it can be easily uncovered. The usual place for a sample to be taken from is the inside of the elbow or wrist, where the veins are relatively close to the surface.
A tight band (tourniquet) is usually put around your upper arm. This squeezes the arm, temporarily slowing down the flow of blood and causing the vein to swell. This makes it easier for a sample to be taken.
Before taking the sample, the phlebotomist will clean the area of skin with an antiseptic wipe.
A needle attached to a syringe or special container is inserted into the vein. The syringe is used to draw out a sample of your blood. You may feel a slight pricking or scratching sensation as the needle goes in, but it shouldn't be too painful. If you don't like needles and blood, tell the person who is taking the sample so they can make you more comfortable.
When the sample has been taken, the tourniquet will be released, and the needle will be removed. Pressure is applied to the skin for a few minutes using a cotton-wool pad. A band-aid may be put on the small wound to keep it clean and to prevent further bleeding.
After the draw
Only a small amount of blood is taken during the test so you shouldn't feel any significant after-effects.
However, some people feel dizzy and faint during and after the test. If this has happened to you in the past, tell the person carrying out the test so they're aware and can help you feel more comfortable.
After the test, you may have a small bruise where the needle went in. Bruises can be painful, but are usually harmless and fade over the next few days.