• Clinical science

Sodium disorders


Sodium is the most important extracellular cation and plays an important role in maintaining the body's extracellular fluid volume. Sodium imbalances typically reflect a dilution or concentration of extracellular fluid rather than an actual loss or gain of sodium. These changes in extracellular fluid volume are mainly due to an increase or decrease in ADH serum levels (which causes the retention and loss of free water respectively). In certain cases, however, sodium imbalances may be the direct result of sodium loss (e.g., following diarrhea, vomiting, or the use of antidiuretics) or excessive sodium intake. Treating sodium imbalances involves careful correction of the sodium deficit/excess and treating the underlying cause. A rapid correction of sodium imbalance can have damaging osmotic effects such as central pontine myelinolysis.





Hypotonic hyponatremia (↓ serum osmolality)

Isotonic hyponatremia (↔︎ serum osmolality)

Hypertonic hyponatremia (↑ serum osmolality)


Hypovolemic hypernatremia

Euvolemic hypernatremia

Hypervolemic hypernatremia


Clinical features

  • Clinical features are primarily neurological and depend on the severity of the sodium imbalance.
    • Mild symptoms
      • Anorexia
      • Nausea
      • Vomiting
      • Headache
      • Muscle cramps
    • Moderate symptoms
    • Severe symptoms
  • Symptoms also depend on the onset of sodium imbalance
    • Acute onset (< 48 hours): usually symptomatic event even with mild sodium derangements
    • Subacute or chronic onset (> 48 hours): usually asymptomatic unless severe derangements are present





General principles

  • Treat underlying cause
  • Patients with serum sodium values < 120 mEq/L or >160 mEq/L require intensive care.
  • Careful correction of sodium levels: maximum correction within 24 hours is 10 mEq/L (rate of correction: 0.5–1 mEq/L per hour)


  • Hypovolemic hyponatremia
    • Mild to moderate symptoms: normal saline
    • Severe symptoms: hypertonic saline
  • Euvolemic hyponatremia
    • Mild to moderate symptoms: fluid restriction
    • Severe symptoms: hypertonic saline
  • Hypervolemic hyponatremia:


The cornerstone of the management of hypernatremia is correcting the free water deficit.

Slow correction to prevent osmotic cell damage!



Osmotic myelinolysis

The symptoms of pontine myelinolysis appear 2 to 6 days after the correction of hyponatremia!



We list the most important complications. The selection is not exhaustive.

  • 1. Li M, Hu YH, Chen G. Hypernatremia severity and the risk of death after traumatic brain injury. Injury. 2013; 44(9): pp. 1213–1218. doi: 10.1016/j.injury.2012.05.021.
  • 2. The Royal Children's Hospital. Hypernatraemia. http://www.rch.org.au/clinicalguide/guideline_index/Hypernatraemia/. Updated December 1, 2012. Accessed February 14, 2017.
  • 3. Verbalis JG, Goldsmith SR, Greenberg A, et al. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013; 126(10): pp. S1–S42. doi: 10.1016/j.amjmed.2013.07.006.
  • 4. Aw TC, Kiechle FL. Pseudohyponatremia. Am J Emerg Med. 1985; 3(3): pp. 236–239. pmid: 3994801.
  • 5. Kim GH. Pseudohyponatremia: Does It Matter in Current Clinical Practice?. Electrolyte Blood Press. 2006; 4(2): pp. 77–82. doi: 10.5049/EBP.2006.4.2.77.
  • 6. Sterns RH. Causes of hyponatremia in adults. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/causes-of-hyponatremia-in-adults?source=search_result&search=hyponatremia&selectedTitle=1~150#H5. Last updated January 11, 2016. Accessed February 14, 2017.
  • 7. Braun MM, Barstow CH, Pyzocha NJ. Diagnosis and management of sodium disorders: hyponatremia and hypernatremia. Am Fam Physician. 2015; 91(5): pp. 299–307. pmid: 25822386.
  • 8. Sterns RH. Manifestations of Hyponatremia and Hypernatremia in Adults. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/manifestations-of-hyponatremia-and-hypernatremia-in-adults. Last updated January 5, 2016. Accessed February 14, 2017.
  • 9. Kasper DL, Fauci AS, Hauser SL, Longo DL, Lameson JL, Loscalzo J. Harrison's Principles of Internal Medicine. New York, NY: McGraw-Hill Education; 2015.
  • 10. Sterns RH. Treatment of hypernatremia. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/treatment-of-hypernatremia. Last updated December 16, 2015. Accessed February 14, 2017.
  • 11. Thurston M, Gaillard F. Osmotic Demyelination Syndrome. https://radiopaedia.org/articles/osmotic-demyelination-syndrome. Updated September 1, 2017. Accessed February 5, 2018.
  • Gankam Kengne F, Soupart A, Pochet R, Brion J-P, Decaux G. Re-induction of hyponatremia after rapid overcorrection of hyponatremia reduces mortality in rats. Kidney Int. 2009; 76(6): pp. 614–621. doi: 10.1038/ki.2009.254.
  • Hage LE, Reineks E, Nasr C. PSEUDOHYPONATREMIA IN THE SETTING OF HYPERCHOLESTEROLEMIA. AACE Clin Case Rep. 2019; 5(2): pp. e172–e174. doi: 10.4158/accr-2018-0309.
  • Espinel CH. The FENa test. Use in the differential diagnosis of acute renal failure. JAMA. 1976; 236(6): pp. 579–581. doi: 10.1001/jama.236.6.579.
  • Hoorn EJ, Zietse R. Diagnosis and Treatment of Hyponatremia: Compilation of the Guidelines. J Am Soc Nephrol. 2017; 28(5): pp. 1340–1349. doi: 10.1681/asn.2016101139.
  • Cluitmans FHM, Meinders AE. Management of severe hyponatremia: Rapid or slow correction?. Am J Med. 1990; 88(2): pp. 161–166. doi: 10.1016/0002-9343(90)90467-r.
  • Herold G. Internal Medicine. Cologne, Germany: Herold G; 2014.
  • Martin RJ. Central pontine and extrapontine myelinolysis: the osmotic demyelination syndromes. J Neurol Neurosurg Psychiatry. 2004; 75(suppl_3): pp. iii22–iii28. doi: 10.1136/jnnp.2004.045906.
  • Sterns RH, Nigwekar SU, Hix JK. The treatment of hyponatremia. Semin Nephrol. 2009; 29(3): pp. 282–99. doi: 10.1016/j.semnephrol.2009.03.002.
  • Claure-Del Granado R, Mehta RL. Fluid overload in the ICU: evaluation and management. BMC Nephrol. 2016; 17(1). doi: 10.1186/s12882-016-0323-6.
  • Davis CP. Dehydration in Adults. In: Stöppler MC. Dehydration in Adults. New York, NY: WebMD. https://www.emedicinehealth.com/dehydration_in_adults/article_em.htm. Accessed October 2, 2019.
  • Spasovski G, Vanholder R, Allolio B, et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Nephrology Dialysis Transplantation. 2014; 29(suppl_2): pp. i1–i39. doi: 10.1093/ndt/gfu040.
  • Agabegi SS, Agabegi ED. Step-Up To Medicine. Baltimore, MD, USA: Wolters Kluwer Health; 2015.
  • Hussain I, Ahmad Z, Garg A. Extreme hypercholesterolemia presenting with pseudohyponatremia - a case report and review of the literature. J Clin Lipidol. 2015; 9(2): pp. 260–264. doi: 10.1016/j.jacl.2014.11.007.
last updated 08/20/2020
{{uncollapseSections(['sG0t03', 'tG0Xa3', '8G0Oa3', 'vG0Aa3', '9G0NY3', 'BG0zY3', 'yG0db3'])}}