Evidence explainerElectrolytes and sodium (salt tablets and electrolyte drinks)

Salt Tablets for Endurance Racing: The 413-Athlete Ironman Trial Found No Difference

Salt pills are a staple in long-course racing. The largest randomized trial found they did not change blood sodium or finishing time, though a smaller half-ironman trial disagreed.

By Kymata Health editorial teamPublished October 9, 2026Last reviewed October 9, 2026

Medical review pending. Written by our editorial team from the studies cited below; a credentialed clinician has not reviewed it yet. Educational only, not medical advice.

Key takeaways

  • In a randomized trial of 413 Ironman finishers, salt tablets (about 3.6 g extra sodium) did not change blood sodium or finishing time versus placebo or nothing [1].
  • Athletes who took no sodium did not need it to avoid low blood sodium [1].
  • In a small trial of 26 triathletes, oral salt was linked to a faster half-ironman time [2].
  • ACSM recommends individual fluid plans because sweat rates and sweat sodium vary widely [3].
  • Most US and Canadian adults already eat more sodium than the 2,300 mg/day risk-reduction level [4].

Safety at a glance

From our Electrolytes and sodium (salt tablets and electrolyte drinks) monograph. Published interactions and cautions only, each with its source.

Who should be careful

  • Daily sodium intake. Most US and Canadian adults already eat more sodium than both the 1,500 mg/day Adequate Intake and the 2,300 mg/day Chronic Disease Risk Reduction Intake, above which reducing intake is advised.[1]
  • Blood pressure. Reducing sodium has a greater effect in adults with hypertension; anyone managing blood pressure should discuss salt tablets with a clinician.[1]
  • Drinking to a plan. ACSM recommends customized fluid plans because sweat rates and sweat electrolyte content vary widely; individual sweat rate can be estimated by weighing before and after exercise.[5]
  • Before you start. Talk to your pharmacist or clinician before adding this supplement, especially if you take prescription medicines, are pregnant or breastfeeding, or have a chronic health condition.[1]

Full Electrolytes and sodium (salt tablets and electrolyte drinks) safety section

The evidence, graded

Pulled from our monograph evidence tables. Grades follow our evidence-grading policy.

  • No effectNo effectBlood sodium and finishing time in an IronmanElectrolytes and sodium (salt tablets and electrolyte drinks) · RCT · n=413 · 2006 · PMID 16505084Sodium tablets did not change post-race serum sodium, finishing time, weight change, rectal temperature or blood pressure compared with placebo or no supplement. Sodium was not needed to prevent hyponatremia in those who took none.
  • Grade DImprovedHalf-ironman race time and body-mass lossElectrolytes and sodium (salt tablets and electrolyte drinks) · RCT · n=26 · 2016 · PMID 25683094Total race time was lower with salt; body-mass loss tended to be smaller and post-race serum sodium and chloride were higher. Post-race strength and jump losses were similar in both groups.

The Ironman trial

At the 2001 Cape Town Ironman, 413 triathletes were randomized to 620 mg table-salt tablets, a starch placebo or no supplement, taking 1 to 4 tablets per hour as they wished [1]. The salt group took in an extra 3.6 g of sodium during the race [1].

There were no significant differences between groups in finishing time or post-race blood sodium [1]. The authors concluded that sodium supplementation was not needed to maintain blood sodium, nor to avoid low sodium in athletes who took none [1].

The trial that found a benefit

A 2016 trial matched 26 experienced triathletes and gave them salt (113 mmol sodium) or a cellulose placebo before and during a half-ironman [2]. Total race time was lower in the salt group, body mass tended to drop less, and post-race blood sodium was higher [2].

Strength and jump losses after the race were similar in both groups, and sweat loss and sweat sodium did not differ [2]. It is one small trial, so we grade it D; the much larger Ironman trial found no performance difference [1].

Fluid matters more than salt

In a small 1991 study, eight people cycled for 6 hours in the heat with water, dilute saline or no fluid [5]. Water and saline performed alike; with no fluid, riders stopped about 1.5 hours early [5].

ACSM recommends customized fluid plans because sweating rates and sweat electrolyte content vary considerably between people, and notes you can estimate your sweat rate by weighing yourself before and after exercise [3]. Its goal is to avoid losing more than 2% of body weight from water deficit [3].

Most people already get plenty

The adult Adequate Intake for sodium is 1,500 mg/day, and the National Academies advise reducing intakes above 2,300 mg/day to lower chronic disease risk [4]. Most US and Canadian population groups already consume more than both [4]. Reducing sodium has a bigger effect in adults with high blood pressure, who should discuss salt tablets with a clinician [4].

For drinks versus water, see electrolyte drinks vs water.

Quick answers

How much sodium is in a salt tablet?

It varies. The Ironman trial used 620 mg tablets of table salt [1]. Check the label for mg of sodium.

Do salt tablets stop cramps?

Our sources did not test cramps, so they cannot answer this [1][2].

Should I take salt tablets for a marathon?

The largest trial, in an Ironman, found no benefit for blood sodium or finishing time [1]. ACSM advises a personal fluid plan based on your sweat rate [3].

Keep reading

Full monographs

Related articles

Browse the full Supplement & Nutrient Encyclopedia or all supplement articles.

References

  1. [1]Sodium supplementation is not required to maintain serum sodium concentrations during an Ironman triathlon. Br J Sports Med, 2006. PMID 16505084
  2. [2]Effects of oral salt supplementation on physical performance during a half-ironman: A randomized controlled trial. Scand J Med Sci Sports, 2016. PMID 25683094
  3. [3]American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc, 2007. PMID 17277604
  4. [4]Dietary Reference Intakes for Sodium and Potassium: Report Highlights. National Academies of Sciences, Engineering, and Medicine, 2019.
  5. [5]Fluid replacement during prolonged exercise: effects of water, saline, or no fluid. Med Sci Sports Exerc, 1991. PMID 1921673

Electrolytes and sodium (salt tablets and electrolyte drinks) and other dietary supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA. Talk to your clinician or pharmacist before starting a supplement, especially if you take prescription medicines. This page has no product or affiliate links.

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