“Drinking more water” may have dangerous implications for long-distance or marathon runners

Tuesday, 03 November 2015 1002 Views 0 Comments
“Drinking more water” may have dangerous implications for long-distance or marathon runners

By Shailja Kaushik

Can you imagine that the commonly held paradigm, ’drink more water’, may have dangerous implications for long-distance or marathon runners?

Drinking excessive water may bring down the sodium levels in the body; a condition known as water retention or over-hydration; in technical terms it is referred to as hyponatremia. According to Lewis Maharam, M.D. Chairman of the International Marathon Medical Directors Association board of governors, hyponatremia is the most serious issue facing new and unconditioned distance runners. [i]

What is hyponatremia?

Hyponatremia means low blood sodium. In medical terms, hyponatremia occurs as the concentration of sodium in serum becomes 135 mml per litre or less. As the serum sodium concentration decreases further to 130 and 120 mmol per litre or less, it is categorised as severe hyponatremia and critical hyponatremia, respectively.

Exercise-associated hyponatremia (EAH) is observed in endurance events. In a study of 488 runners in the 2002 Boston Marathon, 13% of the runners had hyponatremia with 0.6% suffering critical hyponatremia.


While running long-distance, athletes tend to drink higher quantities of water to keep hydrated. This results in reduction in the blood sodium levels which confuses the body and disrupts the functioning of various organs, which may even prove to be life-threatening.

The runners who are finishers or running at slow pace are at greater danger of dehydration and sodium depletion. Amateur runners fall in this category. Most cases of hyponatremia occur on runs of a fairly slow pace that last for more than 4-5 hours.[ii]

Long and slow runs by runners who have been advised to drink regularly, creates the basic conditions for hyponatremia.

Excessive intake of fluid is the primary cause for hyponatremia. Several studies have indicated that there are other risk factors too. These are:

  • Low body weight
  • Exercise duration of more than 4 hours at a stretch
  • Running at a slow pace
  • Inexperience of distance races
  • Drinking lot of fluids
  • Extreme weather conditions (hot/cold)
  • Altered renal water excretory capacity
  • Use of non-steroidal anti-inflammatory drugs (NSAIDs).

Women athletes are at higher risk of developing hyponatremia because they tend to sweat less than men and also lean towards lower body mass.


Usually hyponatremia is considered to be asymptomatic; however its symptoms can be mistaken with those of heat stroke and dehydration. These are

  • Confusion
  • Nausea
  • Cramps
  • Dizziness
  • Headache
  • Fatigue
  • Lack of coordination.


  1. Counsel the participants regarding cooling strategies instead of drinking excessive water. For example, wearing a white mesh cap containing ice cubes to reduce body temperature.
  2. Give up obstacles to sweating such as improper clothing and using too much sunscreen.
  3. Consume sodium to replenish the loss. Low fat salty foods such as pretzels or salted crackers are good oral sources of sodium. Some runners may require salt pills.
  4. As per general guidelines, marathon runners require 400-800 mg of sodium every hour, during warm and cold weather conditions.
  5. If hyponatremia develops, urination may continue to remove the excessive fluid and increase the concentration of blood sodium.


During endurance events such as marathons or triathlons, on-site caregivers should stay alert for runners/athletes developing exercise-associated hyponatremia (EAH). They should correctly diagnose volume depletion. Utmost discretion should be used when hydrating an athlete with intravenous 0.9% saline (sodium chloride) because this may further reduce the serum levels of sodium. The specific treatment method depends on the symptoms exhibited by the athlete. Those presenting with mild, asymptomatic hyponatremia need restricted fluid intake. They must be kept under observation to monitor their serum sodium levels. Spontaneous diuresis may be done.

In the cases of severe or symptomatic hyponatremia, hypertonic saline should be administered because the condition has to be corrected as soon as possible.


Mitchell H. Rosner; Justin Kriveri. Exercise-associated Hyponatremia. Clinical Journal of American Society of Nephrology, 2006.

Julie Heidrich. Hyponatremia in Marathon Runners. Endurance athletes are at risk for this condition secondary to consuming too much fluid during competition.

[i] Dagny Scott Barrios. Runner’s World Guide to Injury Prevention: How to identify problems, Speed Healing and Run Pain-Free, Rodale. 2004.
[ii] Dagny Scott Barrios. Runner’s World Guide to Injury Prevention: How to identify problems, Speed Healing and Run Pain-Free. Rodale, 2004.
[iii] Joseph E. Herrera, Grant Cooper. Essentials of Sports Medicine. Springer Science & Business Media. 2008.

(Dr. Rohan Habbu is an Orthopedic Hand, Nerve & upper Extremity Surgeon. He has done Fellowship in Arthroscopy & Sports Surgery and is an avid runner. To know more, reach out to him on rohanhabbu@gmail.com or +91 982017 13941)

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