context: The brain and spinal cord are surrounded by fluid, called cerebrospinal fluid ( CSF), which protects them from injury, circulates nutrients, and removes waste from the brain. In a spinal tap, also called lumbar puncture, a doctor removes some of that fluid and sends it to a lab for testing. The test can help doctors diagnose disorders that may involve the brain, spinal cord, or their coverings (meninges). If you have headaches or migraines, your doctor may use a spinal tap to look for signs of infection, bleeding in the brain, to measure the pressure around your brain, or other things that could be causing your pain. Tell your doctor about any medications you take, including over-the counter and prescription drugs. Also tell your doctor if you're allergic to any medicine. Do not stop taking your medications without talking with your primary doctor and the doctor who orders the spinal tap. Tell your doctor if you're pregnant (or think you might be), or if you have diabetes. Make sure your doctor knows if you take any blood thinners -- like clopidogrel ( Plavix), dipyridamole ( Persantine), or warfarin ( Coumadin). If you do take blood thinners, ask if and when they should be stopped before the test. Let your doctor know if you have been taking aspirin or any products that contain it, and ask if you should stop taking it before the procedure. Ask your doctor about alcohol use before the test. Generally, you should not drink any beer, wine, or liquor for at least 24 hours beforehand. Make arrangements for someone to take you home when it's over. You should not drive right after the test. Do not bring valuables such as jewelry or credit cards. You'll need to give verbal and written consent for the spinal tap. Be sure to ask your doctor any questions you may have before you give consent. For example, you may want to know about the steps of the procedure and its risks and benefits. If you have diabetes: Make sure your doctor knows that you have diabetes and which medications you are on. Your doctor will likely tell you to take your usual dose of insulin and eat a light breakfast on the morning of your test. When you arrive for the test, be sure to remind the doctor that you have diabetes. Check with your doctor. You may be allowed to eat a light breakfast the morning of the test, or you may be told to fast. The doctor and possibly a nurse or a technologist will be in the room with you during the procedure. You'll get some medicine to help you relax. You'll wear a hospital gown during the test. You will either lie on your side with your knees drawn as close to your chest as possible and your chin toward your chest or sit while leaning over a stable surface. After your care team cleans your back with an antiseptic, they'll place sterile cloths around the area. You'll get a shot of pain-relieving medication injected into the area of your back where they'll draw the fluid. You may feel a slight burning sensation. When the area is numb, the doctor will put a hollow needle in your lower back between two lumbar vertebrae. This sometimes causes pressure. Once the doctor collects enough fluid, he'll remove the needle, clean the area, and cover it with a small bandage. Your doctor may also want to take a blood sample from a vein in your arm and send it to the lab for testing as well. You'll lie on your back or stomach for about an hour. Your care team will keep an eye on you for a few hours. A nurse will also give you instructions on how to take care of yourself. You may feel some discomfort or have a headache. Your doctor will talk with you about the results of the test when they are available. For the first 24 hours after a spinal tap: Your doctor may ask you to stay flat on your back as much as possible. Drink plenty of fluid.