Blood test from a vein
blood draw · venipuncture · phlebotomy · blood work
A nurse takes a small amount of blood from a vein in your arm with a thin needle. One tube of blood can be used for many tests.
For blood chemistry, hormones, infections, clotting, and most other blood tests.
⏱ Duration: usually 3 to 5 minutes
Be sure to tell your doctor
How to prepare
- Food. For many tests, you need to fast for 8 to 12 hours. Plain water is fine. Ask the lab what your tests need.
- The day before. For one day before, avoid alcohol and hard workouts. Try not to smoke in the morning.
- Medicines. Do not stop them on your own. If you take medicines in the morning, ask your doctor whether to take them before or after the test.
- Clothes. Wear a sleeve that rolls up easily above the elbow.
What to bring
- Your test request form or list of tests
- Your ID
How it goes
- You sit down and rest your arm on the armrest
- A band is tied above your elbow and you are asked to make a fist a few times
- The skin is cleaned with antiseptic
- A quick prick: the needle stays in the vein for a few seconds while blood fills the tubes
- The band and needle are removed, and a cotton pad is pressed on the spot
What you'll feel
- A quick prick, like a pinch
- Sometimes slight dizziness. Tell the nurse and you can lie down
Afterwards
- Press the cotton pad for 3 to 5 minutes and keep your arm straight
- A small bruise can happen and goes away on its own
- Results usually take 1 to 3 days. The lab will tell you when
Contact a doctor straight away if
- The spot is very swollen, painful, and red
- Numbness or strong pain in the arm
Common questions
Can I drink water before a blood test?
Yes, plain still water is fine. If you need to fast, skip tea, coffee, and juice.
Why do I feel dizzy after a blood test?
It can happen from nerves or hunger. Sit for a while, drink some water, and eat something sweet.