What Is a Lumbar Puncture?

Let's clear up the fear that puts most people off first: a lumbar puncture is not a needle into the spinal cord itself. It's a test — often called a spinal tap — in which a fine needle is placed into the lower back, into the space where fluid circulates around the cord, below the level where the cord itself ends. That fluid, cerebrospinal fluid or CSF, can then be collected and examined.

The video at the top of this page shows how the procedure is performed, in a concise 1 minute 39 seconds. Watch the positioning and the careful, stepwise approach — there's no rushing here, and that steadiness is the point. A longer explainer on this site, this spinal tap overview, walks through in words what that fluid is and why doctors want a sample of it.

So why would a doctor want that fluid?

CSF bathes the brain and spinal cord, so it can carry clues that a blood test can't. A sample may be sent to the laboratory to look for signs of infection or inflammation, to check for bleeding around the brain in certain situations, or to help investigate other conditions affecting the nervous system. The pressure of the fluid can also be measured during the procedure. In other words, the tap itself is rarely the whole answer — it's how doctors obtain the material that the lab then reads. That fits alongside other nervous-system investigations you may read about here, such as our guide to epilepsy, where tests are likewise used to build a fuller picture rather than relied on alone.

What actually happens, minute by minute

You'll usually be asked to lie on your side with your knees drawn up, or to sit leaning forward — both positions open the spaces between the bones of the lower spine. The skin is cleaned, and a local anaesthetic is used to numb the area first. Once it's numb, the clinician passes the fine needle between two vertebrae in the lower back until it reaches the fluid space, measures the pressure if needed, and collects a small amount of fluid into tubes. Then the needle comes out and a small dressing goes on. People often describe pressure rather than sharp pain during it, though experiences vary — tell the team if you're uncomfortable, because they can pause and help.

Afterwards, and being honest about the headache

You may be asked to rest for a while and drink fluids afterwards, and the team will tell you when you can get up and go home. Some people develop a headache after a lumbar puncture, typically one that feels worse when sitting or standing up; it usually settles, but you should follow the aftercare advice you were given and contact the team if a headache is severe, persistent, or you're worried. Results take time — the lab work, not the tap, is usually the waiting part. If anaesthesia in the spine interests you, our explainer on types of anaesthesia covers spinal anaesthesia, which uses a similar route for a different purpose.

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician and researcher.

Educational only — this article is general information about lumbar puncture, not medical advice and not an instruction to accept or refuse any test. Why a lumbar puncture is or is not appropriate, and how its results apply to you, should be discussed with your own medical team.

Frequently Asked Questions

Does a lumbar puncture hurt?
The area is numbed with local anaesthetic first, so most people feel pressure or a brief pushing sensation rather than sharp pain. Experiences vary, and you can tell the clinician at any point if you're uncomfortable.

Is a spinal tap the same thing as a lumbar puncture?
Yes — they are two names for the same procedure. "Lumbar" refers to the lower back, where the needle is placed, and "spinal tap" is the older, everyday name.

How long do the results take?
It depends on which laboratory tests are run on the fluid. Some checks are quicker than others, and your team will tell you how and when your results will be shared with you.