What Is Phlebotomy?

Medically Reviewed by Carmelita Swiner, MD on July 07, 2023
3 min read

Phlebotomy is when someone uses a needle to take blood from a vein, usually in your arm. Also called a blood draw or venipuncture, it’s an important tool for diagnosing many medical conditions.

Usually the blood is sent to a laboratory for testing. But sometimes the blood is withdrawn as a treatment for certain medical conditions. This is called therapeutic phlebotomy. It removes extra red blood cells, unusually shaped red blood cells, or extra iron in the blood. Therapeutic phlebotomy is used to treat people with:

You won’t have to do anything to prepare for most blood tests. Some require you to fast, or not eat, for 8-12 hours ahead of time. Your doctor should give you instructions before you come in.

To get blood drawn, you’ll sit in a chair or lie down. The person who takes the blood will ask you to make a fist with your hand. Then they’ll tie a band, called a tourniquet, around your upper arm. This makes your veins pop out a little more, which will make it easier to insert the needle in the right place.

You may feel a pinch or sting when the needle goes into your arm. The needle will be attached to a small tube that lets your blood flow into a test tube or bag.

If you’re having blood drawn for tests, you may need to fill one or more test tubes. The process usually takes just a few minutes.

If you’re having blood removed as part of a treatment, the amount of time it takes depends on how much blood is needed. Most of the time it takes 2-3 minutes to get enough blood for a test.

When the lab has the amount they need, the nurse or technician will take the needle out of your arm, remove the tourniquet, and bandage the area. They might ask you to gently press down on the gauze spot for a few minutes until the bleeding stops. You might even wear the bandage for a few hours.

There are few risks. While you may find the process uncomfortable, you should be OK soon afterward.

You could get sick to your stomach if the sight of blood bothers you or if you’re afraid of needles. Don’t feel bad -- this is common. You might even have what’s called a vasovagal reaction. This physical response from your nervous system could make you feel dizzy, break out in a sweat, and cause your heart rate or blood pressure to drop. You could even faint.

Relaxation techniques like deep breathing may help. You can also look at something else to distract yourself.

If you feel dizzy afterward, lie or sit down and put your head between your knees until you stop feeling lightheaded.

Over the next day, you may see redness or bruising where the needle went in. The spot might be a little sore, too. Most side effects go away soon afterward.

The doctor might tell you to drink plenty of fluids, avoid alcohol, and not to exercise for the next few hours.

Humans have been bloodletting for thousands of years. It began with the Egyptians and spread to the Greeks and Romans before reaching Asia and Europe.

The practice once was a commonly used treatment for many medical conditions such as fever, headache, loss of appetite, and digestion issues.

It was considered controversial because doctors sometimes drew very large amounts of blood. This was the case with George Washington, the first president of the United States. In 1799, after being outside in snowy weather, he became ill and developed a fever. To treat him, his doctors drained about 40% of his blood. He died the next night.

Over time, bloodletting was proved to be an ineffective and, in some cases, dangerous treatment. By the end of the 19th century, it wasn’t as common as it once was.

Today, phlebotomy in Western culture is used for medical testing and to treat only a few specific blood diseases.