Urological Health Kidney Disease Print What Is a Sodium Blood Test? What to expect when undergoing this test Medically reviewed by facebook linkedin Medically reviewed by Richard N. Fogoros, MD on August 27, 2019 Richard N. Fogoros, MD, is a retired professor of medicine and board-certified internal medicine physician and cardiologist. He is Verywell's Senior Medical Advisor. Learn about our Medical Review Board Richard N. Fogoros, MD Written by twitter linkedin Written by Jenny Lelwica Buttaccio, OTR/L Jenny Lelwica Buttaccio, OTR/L, is a licensed occupational therapist and advocate for patients with Lyme disease. Learn about our editorial policy Jenny Lelwica Buttaccio, OTR/L Updated on November 13, 2019 More in Urological Health Kidney Disease Renal Test Analyzer Bladder Health Penis Health Prostate Health In This Article Table of Contents Expand Purpose of the Test Risk and Contraindications Before the Test During the Test After the Test Interpreting the Results View All Back To Top Sodium is an electrolyte in the body. Electrolytes carry an electrical charge, and they assist the body in maintaining fluid levels inside and outside of the cells and in the blood. Sodium is crucial for your cells to be able to function properly. Your body ingests most of its sodium in the foods that you eat, and it loses sodium through sweating and urinating. But sometimes, circumstances such as illness, diseases of the kidneys, taking medications (such as diuretics or steroids), consuming too much or too little salt, receiving IV fluids, and more can throw your sodium levels out of whack. Some of the more common symptoms of low sodium (hyponatremia) include: Lethargy or fatigueConfusion or disorientationMuscle twitching or muscle crampsDifficulty walkingSeizures Coma The symptoms of too much sodium (hypernatremia) can be similar to those when the sodium levels are decreased. One main difference, however, is that elevated levels may cause a person to feel especially thirsty. If your healthcare provider suspects there may be an imbalance in your sodium levels, they will order a sodium blood test. The sodium test may also be referred to as "Na test" (Na is the periodic symbol for sodium). Purpose of the Test The use of a sodium test is to determine whether your levels are too low or too high—both of which can cause a variety of symptoms ranging from moderate to severe. It’s not uncommon for a sodium test to be done as part of a metabolic panel, which measures other electrolytes like potassium, chloride, and bicarbonate. The test will help your doctor better understand the amount of sodium in your blood and what may be the factors causing you to feel unwell. Risk and Contraindications Like most blood tests, the risks and contraindications associated with a sodium test are considered slight—blood tests have a low risk of complications. However, one area where you might feel some mild discomfort is when a technician or nurse attempts to draw your blood. A technician may discover that some people have more challenging veins from which to take a blood sample. Consequently, the technician will likely need to insert the needle more than one time, and that process can cause a bit of pain, but only temporarily. Additional problems that could occur during a sodium blood test include: a stinging sensation or minor bruising at the site of the insertion a feeling of faintness or lightheadednessblood collecting under the skin (called a hematoma)bleedingswelling of the vein (called phlebitis)infection (though the risk is low) Note that most of the above symptoms disappear quickly, usually within a day or two. Also, some medications, like diuretics, antidepressants, and others, may alter your sodium levels. Let your doctor know about all the drugs you’re taking, including over-the-counter medications and supplements. Depending on your situation, your doctor might ask you to change your medication schedule for a few days before the test for the most accurate results. Before the Test Typically, there are no specific preparations required to have this blood test. Timing You should be finished with the test itself in a couple of minutes. Location The test may take place in your doctor's office or in another outside facility that conducts bloodwork. What to Wear For clothing, you can wear your usual attire. However, to allow for easy access to your veins, you may choose to wear a shirt that has sleeves you can roll up. Food and Drink If your healthcare provider is doing other blood tests at the same time, you might be asked to fast for several hours before the test (often, overnight). Cost and Insurance One the day of the test, have your insurance card and a form of identification handy so that your blood work can be billed to your insurance carrier. Before the test, you may want to talk with your insurance company about whether or not the test requires pre-approval or what your out-of-pocket expense might be. During the Test Many blood tests are done in a similar manner, so if you’ve had your blood taken before, this process will be more or less the same. First, you’ll likely be seated in a chair so that you can rest the arm from where the blood will be taken. The technician or nurse will place an elastic band around your arm to temporarily restrict the flow of blood and locate a vein. Once they have found the vein, they will disinfect the area using an alcohol swab or pad, then insert the needle. After the needle has been inserted into the vein, the technician will place a small tube at the end of the syringe to collect the sample. When a sufficient amount of blood has been obtained, the technician will remove the elastic and place an adhesive or bandage over the insertion site. After the Test Often, blood tests of this kind are very normal, uneventful procedures. If you notice a bit of pain at the injection site, it should go away in a few days. To prevent bruising, your technician may recommend that you keep the bandage on for a few hours to decrease the likelihood of this happening. Most of the time, there is little to no follow-up instructions after a sodium test, and you’re able to resume your regular activities. Your healthcare provider should notify you once the results are back and provide you with any specific follow-up instructions you might need. Interpreting the Results If your sodium levels are elevated, it could suggest problems with the adrenal glands, kidneys, significant fluid loss, diabetes insipidus, and more. If your sodium levels are decreased, you may be showing signs and symptoms of dehydration, overuse of medications like diuretics, Addison’s disease, heart issues, and certain kidney and liver diseases. Be sure to discuss the results of your test thoroughly with your doctor or healthcare provider. In the event you do have one of these underlying conditions, early treatment is key. A Word From Verywell If your test results fall outside the normal range, your doctor will help you determine the cause. Keep in mind that changes in sodium levels don’t always indicate an illness—they may fluctuate due to other factors such as the medications you’re taking. Be sure to talk to your doctor if you have questions or concerns regarding this test. Addison's Disease Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Weismann D, Schneider A, Höybye C. Clinical aspects of symptomatic hyponatremia. Endocr Connect. 2016;5(5):R35-R43. doi:10.1530/EC-16-0046 Tisdall M, Crocker M, Watkiss J, Smith M. Disturbances of sodium in critically ill adult neurologic patients: a clinical review. J Neurosurg Anesthesiol. 2006;18(1):57-63. Balci AK. General characteristics of patients with electrolyte imbalance admitted to emergency department. World Journal of Emergency Medicine. 2013;4(2):113. doi:10.5847/wjem.j.issn.1920-8642.2013.02.005 Liamis G, Milionis H, Elisaf M. A review of drug-induced hyponatremia. Am J Kidney Dis. 2008;52(1):144-53. doi:10.1053/j.ajkd.2008.03.004 Farquhar WB, Edwards DG, Jurkovitz CT, Weintraub WS. Dietary sodium and health: more than just blood pressure. J Am Coll Cardiol. 2015;65(10):1042-50. doi:10.1016/j.jacc.2014.12.039 Sahay M, Sahay R. Hyponatremia: A practical approach. Indian J Endocrinol Metab. 2014;18(6):760-71. doi:10.4103/2230-8210.141320 Braun MM, Barstow CH, Pyzocha NJ. Diagnosis and management of sodium disorders: hyponatremia and hypernatremia. Am Fam Physician. 2015;91(5):299-307. Additional Reading Balcı AK, Koksal O, Kose A, et al. General characteristics of patients with electrolyte imbalance admitted to emergency department. World Journal of Emergency Medicine.2013; 4(2): 113-6. DOI: 10.5847/wjem.j.issn.1920-8642.2013.02.005 Medline Plus. Sodium Blood Test. Merck Manual. Hypernatremia (High Level of Sodium in the Blood). Merck Manual. Hyponatremia (Low Level of Sodium in the Blood). National Institutes of Health. How the Body Regulates Salt Levels. Continue Reading