Cerebrospinal fluid (CSF) is a clear bodily fluid that cushions and protects your brain and spinal cord. A CSF protein test involves taking a fluid sample from your spinal column using a needle. This procedure is known as a lumbar puncture or spinal tap.

The CSF protein test determines if there’s too much or too little protein in your CSF. Test results that indicate your protein level is higher or lower than normal can help your doctor diagnose a range of conditions. Another use for a CSF protein test is to check the amount of pressure in your spinal fluid.

Your doctor will order a CSF protein test if they suspect you have a central nervous system disease such as multiple sclerosis (MS) or an infectious condition such as meningitis. CSF protein tests are also helpful when looking for signs of injury, bleeding in the spinal fluid, or vasculitis. Vasculitis is another term for inflamed blood vessels.

High levels of protein in your CSF can also indicate:

Acute alcohol use disorder is another possible cause of high protein levels.

Low levels of protein in your CSF could mean your body is leaking cerebrospinal fluid. This could be due to a traumatic injury such as head or spine trauma.

Your doctor will need to know if you’re taking any blood-thinning medications. These might include heparin, warfarin (Coumadin), or aspirin (Bayer). Give your doctor a complete list of medications you take. Make sure to include both prescription and over-the-counter medicines.

Let them know if you have a history of back or spinal problems, or neurological illnesses or conditions. Also tell your doctor if your work is strenuous and involves using your back. You may need to avoid work on the day of your test.

Expect to rest for at least an hour after your test is complete.

The lumbar puncture for your CSF protein test takes place at a hospital or clinic. You need to change into a hospital gown that opens in the back. This gives the doctor easy access to your spine.

To begin, you lie on your side on an exam table or hospital bed, with your back exposed. You might also sit up and bend over a table or a cushion.

Your doctor cleans your back with antiseptic and applies a local anesthetic. This numbs the puncture site to minimize pain. It may take a few moments to start working.

Then, they insert a hollow needle into your lower spine. They draw a small amount of CSF into the needle. You must hold very still while this is happening.

Your doctor removes the needle after collecting enough fluid. They clean and bandage the insertion site. Then they send your CSF sample to a laboratory for analysis.

You can expect to rest for an hour or two after the test. Your doctor may suggest you take a mild pain reliever.

Lumbar puncture is very common and considered generally safe when done by a trained and experienced doctor. However, there are some medical risks, including:

There’s usually some discomfort during the test that may last a little while afterward.

Many people have a headache after a lumbar puncture. This should go away within 24 hours. Let your doctor know if it doesn’t.

Your test results should be ready in a couple of days. The normal range for a protein level is 15 to 45 milligrams per deciliter (mg/dL). Milligrams per deciliter is a measurement that looks at the concentration of something in an amount of fluid.

Children have a lower protein level than adults.

Different laboratories have different ranges they consider normal, which is due to the different ways each laboratory processes samples. Speak with your doctor to find out what your laboratory’s normal range is.

Your doctor will analyze your test results and discuss them with you. If protein levels in your cerebrospinal fluid are higher or lower than normal, your doctor can use these measurements to diagnose a condition or guide additional tests.