Many blood tests don't require any special preparation and take only a few minutes.
Other blood tests require fasting (not eating any food) for 8 to 12 hours before the test. Your doctor will tell you how to prepare for your blood test(s).
Blood usually is drawn from a vein in your arm or other part of your body using a needle. It also can be drawn using a finger prick.
The person who draws your blood might tie a band around the upper part of your arm or ask you to make a fist. Doing this can make the veins in your arm stick out more, which makes it easier to insert the needle.
The needle that goes into your vein is attached to a small test tube. The person who draws your blood removes the tube when it's full, and the tube seals on its own. The needle is then removed from your vein. If you're getting a few blood tests, more than one test tube may be attached to the needle before it's withdrawn.
Some people get nervous about blood tests because they're afraid of needles. Others may not want to see blood leaving their bodies.
If you're nervous or scared, it can help to look away or talk to someone to distract yourself. You might feel a slight sting when the needle goes in or comes out.
Drawing blood usually takes less than 3 minutes.
Once the needle is withdrawn, you'll be asked to apply gentle pressure with a piece of gauze or bandage to the place where the needle was inserted. This helps stop bleeding. It also helps prevent swelling and bruising.
Most of the time, you can remove the pressure after a minute or two. You may want to keep a bandage on for a few hours.
Usually, you don't need to do anything else after a blood test. Results can take anywhere from a few minutes to a few weeks to come back. Your doctor should get the results. It's important that you follow up with your doctor to discuss your test results.