Version July 2025
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What is a lumbar puncture? —
A lumbar puncture, or "LP," is a procedure to get a sample of fluid from around the spinal cord (figure 1). It is also called a "spinal tap."
The spinal cord is a bundle of nerves that runs from the base of the brain down the back. Both the brain and spinal cord are surrounded by "cerebrospinal fluid," or "CSF." The CSF cushions and protects the brain and spinal cord.
CSF can hold important clues about the health of the brain and spinal cord. For example, it can show if there is infection, inflammation, or bleeding in the brain.
Why might my doctor order an LP? —
Your doctor might order an LP to check for problems that affect the brain or spinal cord. Some examples include:
●An infection affecting the brain or spinal cord, such as meningitis
●"Subarachnoid hemorrhage" (figure 2) – This is bleeding in a part of the head called the "subarachnoid space." This is the area between the brain and the thin layer of tissue that covers it.
●Multiple sclerosis – This condition causes inflammation in parts of the brain or spinal cord. This can lead to symptoms like vision problems, numbness and tingling, muscle weakness, and other problems.
●Cancer that has spread to the tissues surrounding the brain or spinal cord
●Nerve problems such as Guillain-Barré syndrome, a condition that causes muscle weakness
●"Pseudotumor cerebri" – This condition can cause bad headaches from too much pressure inside the skull.
●"Normal pressure hydrocephalus" – This is a condition in adults when there is too much spinal fluid in the brain.
Doctors sometimes also do LPs to give certain types of medicines directly into the area surrounding the spinal cord. Examples include:
●Anesthesia (to block pain, like during childbirth or surgery)
●Chemotherapy medicines (to treat cancer)
●Antibiotics
What happens during an LP? —
To prepare for the LP, the doctor will probably ask you to lie on your side and hug your legs, so your back is curved in a "C" shape. Sometimes, they might do the LP when you are seated or lying on your stomach.
When it is time for the procedure:
●It is very important you stay very still. Tell your doctor if you are uncomfortable or do not think you can stay still in that position. Tell the doctor if you feel any numbness, tingling, or other symptoms during the procedure.
●Once you are in the right position, the doctor will feel your spine and choose where to do the LP. It will be in the lower part of your back, below where your spinal cord ends (figure 1). The doctor might also do an ultrasound or use fluoroscopy to guide where to place the needle. An ultrasound uses sound waves to create pictures of the inside of the body. Fluoroscopy is an imaging test that uses X-rays.
●The doctor will clean the area around your lower back with a special liquid. They will drape sterile towels around the area. Then, they will give you a shot to numb the area.
●They will insert a needle into your back, between 2 of the bones (called "vertebrae") that make up the spine. The needle will go straight through your skin and the tissues that surround your spinal cord into the space that is filled with fluid.
●Once the needle is in place, the doctor will measure the fluid pressure. They will also collect a small sample of fluid, or inject medicine if needed. This generally takes several minutes. If the doctor needs to inject medicine, they will do this through the needle.
●When finished, the doctor will remove the needle and place a bandage over the area.
After doing the LP, your doctor might ask you to stay lying down for a half hour or more, before you get up.
What are the risks of an LP? —
Most people do not have problems after an LP. Tell your doctor right away if you have unexpected symptoms.
After an LP, people sometimes get a bad headache. This happens because the spot where the LP needle goes in does not always close up right away. If the hole stays open, CSF can leak out, causing a headache.
In most cases, the hole closes up on its own and the headache goes away in 1 to 2 days. If you get a headache after having an LP, you can take over-the-counter pain medicines. You will probably feel much better if you lie down.
If your headache does not get better after 1 or 2 days, your doctor can offer a treatment called a "blood patch." This involves taking a small amount of your blood and injecting it into the area where the LP was taken. The blood fills in the hole and CSF levels go back to normal, making the headache go away.
Rare problems caused by LP can include:
●Infection
●Bleeding – Before having an LP, it is very important to tell your doctor if you take aspirin or an anticoagulant medicine (also called "blood thinners"). These are used to prevent blood clots. They include warfarin (brand name: Jantoven), apixaban (brand name: Eliquis), edoxaban (brand names: Savaysa, Lixiana), and rivaroxaban (brand name: Xarelto). These medicines could increase your risk of bleeding during the LP procedure. Your doctor might also test your blood to make sure it clots normally.
●Irritation to the nerves that control the eyes or face – This might cause double vision or trouble hearing.
●Bleeding or clots in the veins over the surface of the brain – These are very rare.
●"Cerebral herniation" – This is a very rare but life-threatening problem with the brain. It usually happens only to people who already have a life-threatening brain condition.
●Pain or numbness in the back or legs
●"Epidermoid tumors" – These are abnormal growths that form on the spine long after an LP. They are more likely to happen in children than in adults.
What if my child needs an LP? —
LPs in children are very similar to LPs in adults. But children often need medicines to make them go to sleep before an LP. That's because children usually can't stay still enough for an LP.
How do I care for myself at home? —
Make sure you understand exactly what you need to do to care for yourself. Ask questions if there is anything you do not understand.
You should:
●Drink plenty of fluids for the next day or 2.
●Take an over-the-counter pain medicine, if needed. These include acetaminophen (sample brand name: Tylenol), ibuprofen (sample brand names: Advil, Motrin), and naproxen (sample brand name: Aleve).
When should I call the doctor? —
Call for advice if:
●You have a fever of 100.4°F (38°C) or higher, or chills.
●Clear fluid or blood is coming from where the needle went in
●You have a very bad headache that gets worse when sitting or standing.
●Your legs feel numb, weak, tingly, or painful.
●You have trouble urinating.
Patient education: Spinal headache (The Basics)
Patient education: Bacterial meningitis (The Basics)
Patient education: Viral meningitis (The Basics)
Patient education: Meningitis in children (The Basics)
Patient education: Subarachnoid hemorrhage (The Basics)
Patient education: Multiple sclerosis in adults (The Basics)
Patient education: Multiple sclerosis in children (The Basics)
Patient education: Guillain-Barré syndrome (The Basics)
Patient education: Idiopathic intracranial hypertension (pseudotumor cerebri) (The Basics)
Patient education: Hydrocephalus in babies and children (The Basics)
Patient education: Cytology (The Basics)
Patient education: Meningitis in children (Beyond the Basics)
