The LP medical abbreviation almost always means lumbar puncture, the procedure most people know as a spinal tap, in which a thin needle is placed between two bones of the lower back to collect a small amount of the fluid that surrounds the brain and spinal cord. That fluid, called cerebrospinal fluid or CSF, is then tested in the lab.
In emergency, neurology and pediatric notes, LP means the procedure. In a skin clinic or an eye exam, though, the same two letters can mean something quite different, so the setting matters. Below are the main meanings, how a typical LP note reads, and what the numbers in it refer to.
At a glance
Stands for
Lumbar puncture (spinal tap)Other meanings
Lichen planus (dermatology); light perception (eye exams)Used in
Emergency care, neurology, pediatrics, oncology, anesthesiaCollects
Cerebrospinal fluid from the lower backWhere you see it
Procedure notes, consent forms, lab orders, discharge summariesDo not confuse with
LPN (licensed practical nurse) and Lp(a), a cholesterol particle test
Lumbar puncture, the main meaning of LP
Lumbar refers to the lower back, and puncture means a small hole made by a needle. During the procedure the person either lies curled on one side or sits leaning forward, which opens the spaces between the vertebrae. After the skin is cleaned and numbed, the clinician passes a fine needle into the fluid filled space below where the spinal cord ends, so the cord itself is not in the needle's path.
Doctors order an LP to look for infection such as meningitis, bleeding around the brain, inflammation, certain cancers, or pressure problems. It can also be used to give medicine or anesthesia into the spinal fluid. The procedure usually takes well under an hour.
Reading an LP note line by line
A bedside LP note follows a familiar order: the procedure, the pressure, how the fluid looked, and which tests were sent.
| Phrase | Plain meaning |
|---|---|
| LP at bedside | Lumbar puncture done in the patient's room |
| opening pressure 18 cm H2O | Fluid pressure when the needle first entered, measured in centimeters of water |
| CSF clear | The fluid looked colorless and see through, which is the usual look |
| sent for cell count | Lab will count white and red blood cells in the sample |
An emergency department handoff: "Febrile infant, LP done, CSF pending, started on antibiotics." Here the team has collected spinal fluid to check for infection and is waiting for results. This is an example of how the phrase is used, not guidance for any case.
Other meanings of LP and how to tell them apart
Two other expansions show up often enough to know. In dermatology, LP stands for lichen planus, an inflammatory condition that causes itchy, flat topped purple bumps on the skin and can affect the mouth. In an eye exam, LP means light perception, a level of vision where a person can tell light from dark but cannot count fingers or see hand motion.
| Setting | LP usually means | Clue in the note |
|---|---|---|
| Neurology, ED, pediatrics | Lumbar puncture | Mentions CSF, needle level, opening pressure |
| Dermatology | Lichen planus | Describes a rash, biopsy or mouth lesions |
| Ophthalmology | Light perception | Sits in a visual acuity line with HM or CF |
If the surrounding words do not make it obvious, a quick question to whoever charted it settles the matter.
Recovery and common side effects
The most talked about after effect is a post LP headache, which tends to be worse when sitting or standing and better lying flat. It happens because a little fluid can leak from the needle hole for a time. Most such headaches settle on their own, and the care team has treatments if one lingers. Mild back soreness at the needle site is also common.
Discharge papers usually list signs that need a call back, such as fever, new weakness, numbness or a headache that does not ease.
These are general facts about the procedure. Your own care team can explain why a spinal tap was suggested in your case and what aftercare they recommend.
Frequently asked questions
What does LP mean in a hospital note?
In most hospital notes LP refers to a lumbar puncture, the procedure many people know as a spinal tap. It describes collecting a sample of the fluid around the brain and spinal cord through a needle in the lower back.
Is an LP the same as a spinal tap?
Yes. Spinal tap is the everyday name and lumbar puncture is the medical name for the same procedure.
What does LP mean on an eye exam?
On a vision chart LP means light perception. The person can sense whether a light is on or off but cannot see shapes, hand movement or fingers at that point in the exam.
Does a lumbar puncture touch the spinal cord?
The needle is placed below the level where the spinal cord usually ends, in a space that holds fluid and nerve roots. That is why the lower back is chosen for the procedure.
Why do doctors check opening pressure during an LP?
Opening pressure shows how much pressure the spinal fluid is under. A high or low reading can point toward certain conditions, and each lab defines its own normal range.