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Exercise-associated hyponatremia

Mitchell H Rosner, MD
Tamara Hew-Butler, DPM, PhD
Section Editor
Richard H Sterns, MD
Deputy Editor
John P Forman, MD, MSc


Severe and potentially life-threatening hyponatremia can occur during or following exercise, particularly in athletes participating in endurance events such as marathons (42.2 km), triathlons (3.8 km swim, 180 km cycling, and 42.2 km running), and ultradistance (100 km) races [1-4]. A similar problem can occur during short-duration exercise (eg, American football), military operations, and desert hikes.

Exercise-associated hyponatremia (EAH) was first described in Durban, South Africa in 1981 and in 1985 in four athletes participating in endurance events longer than seven hours [5]. Prior to 1981, athletes were advised to avoid drinking during exercise, leading to the development of hypernatremia in some athletes [6,7]. Subsequently, athletes were advised to consume as much fluid as possible during exercise. Concomitant with these recommendations, the incidence of hyponatremia in endurance athletes appeared to increase, particularly in the United States.

The majority of athletes who develop hyponatremia are asymptomatic or mildly symptomatic (eg, weakness, dizziness, headache, lethargy, nausea/vomiting). However, severe manifestations can occur, including seizures, cerebral edema, noncardiogenic pulmonary edema, and death. (See 'Clinical manifestations' below and "Manifestations of hyponatremia and hypernatremia in adults".)


The 2015 Third International Exercise-Associated Hyponatremia Consensus Development Conference defined exercise-associated hyponatremia (EAH) as hyponatremia (serum or plasma sodium below the normal reference range of the laboratory) occurring during or up to 24 hours after prolonged physical activity [8].


Prior to the recognition that drinking large volumes of water can lead to potentially fatal hyponatremia, it was not rare for endurance athletes to be hyponatremic at the end of the race, usually in the absence of overt central nervous system symptoms [1,2,9-17]. The incidence of hyponatremia has varied, ranging from 0 to 18 percent in marathoners and triathletes [2,10,14-16] to 51 percent of runners participating in a 161 km mountain footrace, which suggests that exercise-associated hyponatremia (EAH) may be more prevalent in extreme endurance events lasting more than 24 hours [17].

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Literature review current through: Oct 2017. | This topic last updated: Jan 13, 2016.
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  1. Almond CS, Shin AY, Fortescue EB, et al. Hyponatremia among runners in the Boston Marathon. N Engl J Med 2005; 352:1550.
  2. Noakes TD, Sharwood K, Speedy D, et al. Three independent biological mechanisms cause exercise-associated hyponatremia: evidence from 2,135 weighed competitive athletic performances. Proc Natl Acad Sci U S A 2005; 102:18550.
  3. Frizzell RT, Lang GH, Lowance DC, Lathan SR. Hyponatremia and ultramarathon running. JAMA 1986; 255:772.
  4. Sallis RE. Fluid balance and dysnatremias in athletes. Curr Sports Med Rep 2008; 7:S14.
  5. Noakes TD, Goodwin N, Rayner BL, et al. Water intoxication: a possible complication during endurance exercise. Med Sci Sports Exerc 1985; 17:370.
  6. Wyndham CH, Strydom NB. The danger of an inadequate water intake during marathon running. S Afr Med J 1969; 43:893.
  7. Noakes TD. Overconsumption of fluids by athletes. BMJ 2003; 327:113.
  8. Hew-Butler T, Rosner MH, Fowkes-Godek S, et al. Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Clin J Sport Med 2015; 25:303.
  9. Davis DP, Videen JS, Marino A, et al. Exercise-associated hyponatremia in marathon runners: a two-year experience. J Emerg Med 2001; 21:47.
  10. Sharwood K, Collins M, Goedecke J, et al. Weight changes, sodium levels, and performance in the South African Ironman Triathlon. Clin J Sport Med 2002; 12:391.
  11. Noakes TD, Norman RJ, Buck RH, et al. The incidence of hyponatremia during prolonged ultraendurance exercise. Med Sci Sports Exerc 1990; 22:165.
  12. Hew TD, Chorley JN, Cianca JC, Divine JG. The incidence, risk factors, and clinical manifestations of hyponatremia in marathon runners. Clin J Sport Med 2003; 13:41.
  13. Montain SJ, Sawka MN, Wenger CB. Hyponatremia associated with exercise: risk factors and pathogenesis. Exerc Sport Sci Rev 2001; 29:113.
  14. Wharam PC, Speedy DB, Noakes TD, et al. NSAID use increases the risk of developing hyponatremia during an Ironman triathlon. Med Sci Sports Exerc 2006; 38:618.
  15. Reid SA, Speedy DB, Thompson JM, et al. Study of hematological and biochemical parameters in runners completing a standard marathon. Clin J Sport Med 2004; 14:344.
  16. Speedy DB, Noakes TD, Rogers IR, et al. Hyponatremia in ultradistance triathletes. Med Sci Sports Exerc 1999; 31:809.
  17. Lebus DK, Casazza GA, Hoffman MD, Van Loan MD. Can changes in body mass and total body water accurately predict hyponatremia after a 161-km running race? Clin J Sport Med 2010; 20:193.
  18. Hew-Butler T, Sharwood K, Boulter J, et al. Dysnatremia predicts a delayed recovery in collapsed ultramarathon runners. Clin J Sport Med 2007; 17:289.
  19. Hoffman MD, Stuempfle KJ, Rogers IR, et al. Hyponatremia in the 2009 161-km Western States Endurance Run. Int J Sports Physiol Perform 2012; 7:6.
  20. Knechtle B, Knechtle P, Rosemann T. Low prevalence of exercise-associated hyponatremia in male 100 km ultra-marathon runners in Switzerland. Eur J Appl Physiol 2011; 111:1007.
  21. Verbalis JG. Renal function and vasopressin during marathon running. Sports Med 2007; 37:455.
  22. Siegel AJ, Verbalis JG, Clement S, et al. Hyponatremia in marathon runners due to inappropriate arginine vasopressin secretion. Am J Med 2007; 120:461.e11.
  23. Dugas J. Sodium ingestion and hyponatraemia: sports drinks do not prevent a fall in serum sodium concentration during exercise. Br J Sports Med 2006; 40:372.
  24. Ayus JC, Varon J, Arieff AI. Hyponatremia, cerebral edema, and noncardiogenic pulmonary edema in marathon runners. Ann Intern Med 2000; 132:711.
  25. Baker J, Cotter JD, Gerrard DF, et al. Effects of indomethacin and celecoxib on renal function in athletes. Med Sci Sports Exerc 2005; 37:712.
  26. Halperin ML, Kamel KS, Sterns R. Hyponatremia in marathon runners. N Engl J Med 2005; 353:427.
  27. Olsson KE, Saltin B. Variation in total body water with muscle glycogen changes in man. Acta Physiol Scand 1970; 80:11.
  28. Rose BD, Post TW. Clinical Physiology of Acid-Base and Electrolyte Disorders, 5th ed, McGraw-Hill, New York 2001. p.285.
  29. Rosner MH, Kirven J. Exercise-associated hyponatremia. Clin J Am Soc Nephrol 2007; 2:151.
  30. Speedy DB, Noakes TD, Kimber NE, et al. Fluid balance during and after an ironman triathlon. Clin J Sport Med 2001; 11:44.
  31. Galun E, Tur-Kaspa I, Assia E, et al. Hyponatremia induced by exercise: a 24-hour endurance march study. Miner Electrolyte Metab 1991; 17:315.
  32. Hew-Butler T, Jordaan E, Stuempfle KJ, et al. Osmotic and nonosmotic regulation of arginine vasopressin during prolonged endurance exercise. J Clin Endocrinol Metab 2008; 93:2072.
  33. Merry TL, Ainslie PN, Walker R, Cotter JD. Fitness alters fluid regulatory but not behavioural responses to hypohydrated exercise. Physiol Behav 2008; 95:348.
  34. Hew-Butler T, Dugas JP, Noakes TD, Verbalis JG. Changes in plasma arginine vasopressin concentrations in cyclists participating in a 109-km cycle race. Br J Sports Med 2010; 44:594.
  35. Freund BJ, Shizuru EM, Hashiro GM, Claybaugh JR. Hormonal, electrolyte, and renal responses to exercise are intensity dependent. J Appl Physiol (1985) 1991; 70:900.
  36. Beardwell CG, Geelen G, Palmer HM, et al. Radioimmunoassay of plasma vasopressin in physiological and pathological states in man. J Endocrinol 1975; 67:189.
  37. van Nieuwenhoven MA, Vriens BE, Brummer RJ, Brouns F. Effect of dehydration on gastrointestinal function at rest and during exercise in humans. Eur J Appl Physiol 2000; 83:578.
  38. Rowe JW, Shelton RL, Helderman JH, et al. Influence of the emetic reflex on vasopressin release in man. Kidney Int 1979; 16:729.
  39. Baylis PH, Zerbe RL, Robertson GL. Arginine vasopressin response to insulin-induced hypoglycemia in man. J Clin Endocrinol Metab 1981; 53:935.
  40. Chiodera P, Coiro V. Endogenous opioid mediation of somatostatin inhibition of arginine vasopressin release evoked by insulin-induced hypoglycemia in man. J Neural Transm Gen Sect 1991; 83:121.
  41. Takamata A, Mack GW, Stachenfeld NS, Nadel ER. Body temperature modification of osmotically induced vasopressin secretion and thirst in humans. Am J Physiol 1995; 269:R874.
  42. Cairns RS, Hew-Butler T. Incidence of Exercise-Associated Hyponatremia and Its Association With Nonosmotic Stimuli of Arginine Vasopressin in the GNW100s Ultra-endurance Marathon. Clin J Sport Med 2015; 25:347.
  43. Montain SJ, Laird JE, Latzka WA, Sawka MN. Aldosterone and vasopressin responses in the heat: hydration level and exercise intensity effects. Med Sci Sports Exerc 1997; 29:661.
  44. McConell GK, Burge CM, Skinner SL, Hargreaves M. Influence of ingested fluid volume on physiological responses during prolonged exercise. Acta Physiol Scand 1997; 160:149.
  45. EDELMAN IS, JAMES AH, BROOKS L, MOORE FD. Body sodium and potassium. IV. The normal total exchangeable sodium; its measurement and magnitude. Metabolism 1954; 3:530.
  46. EDELMAN IS, JAMES AH, BADEN H, MOORE FD. Electrolyte composition of bone and the penetration of radiosodium and deuterium oxide into dog and human bone. J Clin Invest 1954; 33:122.
  47. Lindinger MI, Heigenhauser GJ, McKelvie RS, Jones NL. Blood ion regulation during repeated maximal exercise and recovery in humans. Am J Physiol 1992; 262:R126.
  48. Buono MJ, Ball KD, Kolkhorst FW. Sodium ion concentration vs. sweat rate relationship in humans. J Appl Physiol (1985) 2007; 103:990.
  49. Shibasaki M, Wilson TE, Crandall CG. Neural control and mechanisms of eccrine sweating during heat stress and exercise. J Appl Physiol (1985) 2006; 100:1692.
  50. Buono MJ, Sjoholm NT. Effect of physical training on peripheral sweat production. J Appl Physiol (1985) 1988; 65:811.
  51. Yamazaki F, Fujii N, Sone R, Ikegami H. Mechanisms of potentiation in sweating induced by long-term physical training. Eur J Appl Physiol Occup Physiol 1994; 69:228.
  52. Nadel ER, Pandolf KB, Roberts MF, Stolwijk JA. Mechanisms of thermal acclimation to exercise and heat. J Appl Physiol 1974; 37:515.
  53. Speedy DB, Rogers IR, Noakes TD, et al. Exercise-induced hyponatremia in ultradistance triathletes is caused by inappropriate fluid retention. Clin J Sport Med 2000; 10:272.
  54. Speedy DB, Noakes TD, Rogers IR, et al. A prospective study of exercise-associated hyponatremia in two ultradistance triathletes. Clin J Sport Med 2000; 10:136.
  55. Hew-Butler T, Collins M, Bosch A, et al. Maintenance of plasma volume and serum sodium concentration despite body weight loss in ironman triathletes. Clin J Sport Med 2007; 17:116.
  56. Young M, Sciurba F, Rinaldo J. Delirium and pulmonary edema after completing a marathon. Am Rev Respir Dis 1987; 136:737.
  57. Hew-Butler T, Anley C, Schwartz P, Noakes T. The treatment of symptomatic hyponatremia with hypertonic saline in an Ironman triathlete. Clin J Sport Med 2007; 17:68.
  58. Siegel AJ, d'Hemecourt P, Adner MM, et al. Exertional dysnatremia in collapsed marathon runners: a critical role for point-of-care testing to guide appropriate therapy. Am J Clin Pathol 2009; 132:336.
  59. Ellis C, Cuthill J, Hew-Butler T, et al. Case report: exercise-associated hyponatremia with rhabdomyolysis during endurance exercise. Phys Sportsmed 2009; 37:126.
  60. Bruso JR, Hoffman MD, Rogers IR, et al. Rhabdomyolysis and hyponatremia: a cluster of five cases at the 161-km 2009 Western States Endurance Run. Wilderness Environ Med 2010; 21:303.
  61. Owen BE, Rogers IR, Hoffman MD, et al. Efficacy of oral versus intravenous hypertonic saline in runners with hyponatremia. J Sci Med Sport 2014; 17:457.
  62. Ayus JC, Arieff A, Moritz ML. Hyponatremia in marathon runners. N Engl J Med 2005; 353:427.
  63. Adrogué HJ, Madias NE. Hyponatremia. N Engl J Med 2000; 342:1581.
  64. Sterns RH, Nigwekar SU, Hix JK. The treatment of hyponatremia. Semin Nephrol 2009; 29:282.
  65. Cheuvront SN, Haymes EM. Ad libitum fluid intakes and thermoregulatory responses of female distance runners in three environments. J Sports Sci 2001; 19:845.
  66. Speedy DB, Rogers IR, Noakes TD, et al. Diagnosis and prevention of hyponatremia at an ultradistance triathlon. Clin J Sport Med 2000; 10:52.
  67. USATF Self-Testing Program for Optimal Hydration. https://www.usatf.org/groups/Coaches/library/2007/hydration/USATFSelfTestingProgramForOptimalHydration.pdf (Accessed on May 12, 2014).
  68. Hew-Butler T, Verbalis JG, Noakes TD, International Marathon Medical Directors Association. Updated fluid recommendation: position statement from the International Marathon Medical Directors Association (IMMDA). Clin J Sport Med 2006; 16:283.
  69. Noakes T. Sodium ingestion and the prevention of hyponatraemia during exercise. Br J Sports Med 2004; 38:790.
  70. Speedy DB, Thompson JM, Rodgers I, et al. Oral salt supplementation during ultradistance exercise. Clin J Sport Med 2002; 12:279.