Lumbar puncture

A lumbar puncture, also known as a spinal tap, is a procedure that collects a sample of cerebrospinal fluid. This is the fluid that surrounds and protects the spinal cord and brain. Your physician may recommend this test after conducting a neurologic exam to confirm a neurologic diagnosis.

Why is a lumbar puncture performed?

A spinal tap is used to help diagnose and/or rule out a number of conditions including:

A lumbar puncture can be done in an outpatient or inpatient setting. This page describes the procedure done in an outpatient setting.

Preparing for the procedure in an outpatient setting

Your doctor will give you instructions on how to prepare for a lumbar puncture. You may be asked to not drink or eat anything the night before your procedure. Be sure to tell your doctor about any medications you may be taking or allergies to medication.

What happens during the procedure?

You'll change into a gown, with the opening to the back. Your physician may ask you to lie on your side on the exam table, with your knees pulled up toward your chest, or you may be asked to sit on the side of the table with your arms hanging forward. These positions help increase the space between your vertebrae.

Your back will be cleaned with antiseptic solution, and you'll receive an injection of anesthetic to numb your lower back. The injection may sting, but it will help reduce discomfort for the lumbar puncture.

Your doctor then carefully will insert a thin needle into the spinal canal in your lower back. You may feel pressure as the doctor does this. Your doctor will remove a small sample of fluid, remove the needle, and then place a bandage at the site of the puncture.

After the test, you'll be told to lie flat for an hour to help reduce the possibility of a headache that some patients experience after a lumbar puncture.

You'll need to have someone drive you home. Limit activities and driving for the next 24 hours.


Most people do not experience complications from a lumbar puncture. If you do experience any of the following, let your doctor know:

  • Headache: The most common complication is a headache. Lying flat after the procedure helps reduce the likelihood of having a headache.
  • Bleeding or pain at injection site
  • Infection
  • Brain herniation