First Aid Heat & Cold Exposure An Overview of Hyponatremia Cause, Symptoms, and Treatment of Abnormally Low Sodium By Rod Brouhard, EMT-P Updated on May 12, 2022 Medically reviewed by Michael Menna, DO Print Table of Contents View All Table of Contents Causes Symptoms Diagnosis Treatment Too little sodium in the body—an electrolyte disorder called hyponatremia—usually occurs when the body fails to remove water normally. In other words, the body either loses or retains too much water, which ultimately affects the body's sodium content. Symptoms of hyponatremia, or low sodium in the body, may include nausea and vomiting, confusion, weakness, and in severe cases, seizures, coma, and even death. In order to diagnose hyponatremia, a healthcare provider will perform a medical history, physical examination, and order laboratory tests. Treatment involves addressing the underlying cause—such as administering a salt-water solution through the vein, or alternatively, restricting water and salt intake. A normal sodium level is between 135 and 145 milliequivalents per liter (mEq/L). Hyponatremia is defined as a sodium level of less than 135 mEq/L. Causes The causes of hyponatremia are typically classified by the amount of fluid in the body and broken down into three categories: Hypovolemic hyponatremia (low volume)Euvolemic hyponatremia (normal volume)Hypervolemic hyponatremia (high volume) Hypovolemic Hyponatremia Hypovolemic hyponatremia occurs when the body loses too much water with an even greater decrease in the sodium level. Usually, the fluid loss is from the kidneys (for example, the overuse of diuretics) or the digestive tract (such as severe or persistent vomiting or diarrhea). Hypovolemic hyponatremia is common at endurance sporting events, affecting as many as 6% of endurance cyclists, 8% of marathon runners, 11% of Ironman competitors, and 67% of ultramarathon contestants. Primary adrenal insufficiency, known as Addison's disease, is another common cause of hypovolemic hyponatremia. Euvolemic Hyponatremia Euvolemic hyponatremia occurs when the total amount of water in the body is increased, but the sodium level remains normal. This may happen with athletes who engage in intense exercises, like a marathon or triathlon, and then drink too much water. It is also seen in people who consume excess amounts of alcohol or use the drug ecstasy. Malnutrition, severe hypothyroidism, and a water-retaining condition called syndrome of inappropriate antidiuretic hormone secretion (SIADH) can also cause euvolemic hyponatremia. Hypervolemic Hyponatremia Hypervolemic hyponatremia occurs when the body holds on to too much water, relative to its sodium content. Medical conditions that may cause this type of hyponatremia, include: Heart failure Cirrhosis Kidney disease Symptoms The symptoms of hyponatremia depend on the rate at which the sodium level dropped and the severity of the drop. In fact, many people with hyponatremia have no symptoms—instead, the electrolyte abnormality is found incidentally through a blood test drawn for other purposes. Illustration by Nusha Ashjaee, Verywell Hyponatremia may cause a variety of potential symptoms including: WeaknessHeadacheNausea and vomitingMuscle crampsRestlessness or irritabilitySlurred speechConfusion Signs of volume overload (too much water) can manifest with edema (swelling of the limbs) or ascites (accumulation of fluids in the abdomen). By contrast, people with hypovolemic hyponatremia will often have signs of dehydration from volume loss (including dry mouth, decreased skin elasticity, and orthostatic hypotension). In severe cases where sodium levels drop below 120 mEq/L, seizure and coma may occur along with acute encephalitis (brain swelling), brain damage, and even death. Causes and Symptoms of Dehydration Diagnosis The diagnosis of hyponatremia involves a medical history, physical examination, and various laboratory tests. Physical Examination In addition to reviewing your symptoms and medical history, your healthcare provider will perform a physical exam to check for dehydration and edema. A simple, in-office neurological exam may also be performed. Laboratory Tests The sodium level can be measured within a simple blood test, called a basic or complete metabolic panel. In addition, the following tests may be ordered to make a diagnosis of hyponatremia: Complete metabolic panel Urine sodium level Urine creatinine level Serum and urine osmolality Other laboratory tests may be ordered to determine the underlying cause of hyponatremia. This may include a thyroid-stimulating hormone (TSH) test, cortisol test, or adrenocorticotropic hormone (ACTH) stim test. Treatment The treatment of hyponatremia is complex and varies based on the underlying cause and other factors, such as: The presence or absence of symptomsThe severity of the sodium lossWhether hyponatremia is acute or chronicYour volume status For example, for hypervolemic hyponatremia caused by heart failure or cirrhosis, treatment may involve the restriction of salt and water as well as the use of diuretics to remove excess fluid. On the other hand, for hypovolemic hyponatremia from severe vomiting or diarrhea, a saline solution may be delivered intravenously (into a vein). Other therapies may include: Taking salt tablets or increasing salt intakeDiscontinuing or cutting back on medications that cause hyponatremiaTaking medications called vasopressin antagonists (vaptans) that help treat hyponatremia in people with heart failure, cirrhosis or SIADH It is important to treat hyponatremia promptly and appropriately. People hospitalized for hyponatremia are at an increased risk of severe illness and death. Hyponatremia also affects between 10% and 30% of people admitted to hospital, according to a 2016 review in the European Journal of Internal Medicine. A Word From Verywell Hyponatremia is a common electrolyte condition that varies considerably in severity and etiology. Being knowledgeable of the potential symptoms and causes is a key first step to understanding this disorder. If you are concerned about your sodium level. be sure to discuss it with your healthcare provider. 4 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Lu DY, Cheng HM, Cheng YL, et al. Hyponatremia and worsening sodium levels are associated with long-term outcome in patients hospitalized for acute heart failure. J Am Heart Assoc. 2016;5(3):e002668. doi:10.1161/JAHA.115.002668 Hew-Butler T, Loi V, Pani A, Rosner MH. Exercise-associated hyponatremia: 2017 update. Front Med (Lausanne). 2017;4:21. doi:10.3389/fmed.2017.00021 Nardone R, Brigo F, Trinka E. Acute symptomatic seizures caused by electrolyte disturbances. J Clin Neurol. 2016;12(1):21-33. doi:10.3988/jcn.2016.12.1.21 Filippatos TD, Liamis G, Christopoulou F, Elisaf MS. Ten common pitfalls in the evaluation of patients with hyponatremia. Eur J Intern Med. 2016;29:22-5. doi:10.1016/j.ejim.2015.11.022 Additional Reading Braun MM, Barstow CH, Pyzocha NJ. Diagnosis and management of sodium disorders: hyponatremia and hypernatremia. Am Fam Physician. 2015 Mar;91(5):299-307. Sahay M, Sahay R. Hyponatremia: A practical approach. Indian J Endocrinol Metab. 2014 Nov-Dec;18(6):760-71. doi:10.4103/2230-8210.141320 By Rod Brouhard, EMT-P Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients. See Our Editorial Process Meet Our Medical Expert Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit