Electrolytes and sodium (salt tablets and electrolyte drinks)
Summary
In a randomized trial of 413 Ironman triathletes, salt tablets did not change blood sodium or finishing time. A small half-ironman trial found faster race times and less body-mass loss with salt. ACSM advises individual fluid plans because sweat sodium varies. Most adults already eat more sodium than the 2,300 mg/day risk-reduction level.
Key facts
- Salt (sodium chloride) tablets or capsules, and electrolyte or sports drinks containing sodium[2][5]
- Sodium chloride is about 39% sodium by weight. No head-to-head trials of tablets versus drinks in our sources[8][9]
- Blood sodium and finish time in Ironman racing: no difference (no-effect); half-ironman race time ↓ in one small trial (D); 6-hour cycling with water vs saline: no difference (D)[2][3][4]
- Adult Adequate Intake 1,500 mg/day; Chronic Disease Risk Reduction Intake: reduce intakes above 2,300 mg/day. No UL[1]
- 3 graded human outcomes on this page
- October 8, 2026
How it works
EstablishedSweat removes water and sodium, and both sweat rate and sweat sodium vary widely between people (established). Drinking during exercise aims to avoid excessive dehydration (over 2% of body weight) and large shifts in electrolytes; beverages with electrolytes and carbohydrate can help more than water in some situations (established). In one small trial, more sodium during a 4-hour ride reduced urine output and expanded extracellular fluid but did not change cardiovascular drift or thermoregulation.[5][7]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Half-ironman race time and body-mass loss | Improved | Grade D | RCT · n = 26 · 2016 Experienced triathletes in a real half-ironman race Form: oral salt vs cellulose placebo · Dose: 113 mmol sodium and 112 mmol chloride before and during the race · Duration: Single race Total 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. | 25683094 (opens PubMed)Source [3] |
| 6-hour cycling in the heat: water vs saline vs no fluid | No effect | Grade D | Crossover RCT · n = 8 · 1991 Five men and three women cycling at 55% VO2max at 30 °C Form: saline (25 mmol/L sodium) vs water, matched to losses · Dose: Enough fluid to balance sweat and urine losses · Duration: Three 6-hour trials Water and saline gave no significant differences in heart rate, body temperature, plasma sodium or perceived exertion; plasma sodium fell during both. With no fluid, participants stopped about 1.5 hours early. | 1921673 (opens PubMed)Source [4] |
| Blood sodium and finishing time in an Ironman | No effect | No effect | RCT · n = 413 · 2006 Triathletes completing the 2001 Cape Town Ironman, randomized to sodium tablets, placebo or nothing Form: table-salt tablets (620 mg) vs starch placebo · Dose: 1–4 tablets per hour as desired; about 3.6 g extra sodium over the race · Duration: Single race (about 12 hours) Sodium 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. | 16505084 (opens PubMed)Source [2] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Salt (sodium chloride) tablets or capsules | 39.3%[8][9] | No head-to-head human data versus drinks in our sources.[2] | No adverse differences versus placebo in the Ironman trial (blood pressure, temperature, sodium).[2] | Ironman and half-ironman racing |
| Electrolyte and sports drinks | Varies[5] | Beverages with electrolytes and carbohydrate can provide benefits over water alone in certain circumstances (ACSM).[5] | No form-specific tolerance data in our sources.[5] | Fluid replacement during prolonged exercise |
Compound weight → elemental electrolytes
500 mg salt (sodium chloride) tablets or capsules ≈ 197 mg elemental electrolytes
Studied doses
Doses studied in human trials ranged from about 700 mg of sodium per hour of racing to about 3.6 g of extra sodium across a 12-hour Ironman, taken only during the event.[2][6]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
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]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Articles about Electrolytes and sodium (salt tablets and electrolyte drinks)
Plain-English answers to common questions, built on the evidence above.
Frequently asked questions
Do I need salt tablets for an Ironman?
In a randomized trial of 413 Ironman finishers, salt tablets (about 3.6 g extra sodium) did not change blood sodium, finishing time or weight change compared with placebo or nothing. The authors concluded supplemental sodium was not needed to preserve blood sodium.[2]
Can salt improve race times?
One small trial in 26 triathletes found a faster half-ironman time with oral salt, along with higher blood sodium after the race. It has not been confirmed in larger trials.[3]
Are electrolyte drinks better than water?
ACSM says beverages containing electrolytes and carbohydrate can provide benefits over water alone in certain circumstances. In a 6-hour cycling study, matched volumes of water and dilute saline performed alike; drinking enough mattered more.[5][4]
How much sodium do adults need?
The adult Adequate Intake is 1,500 mg/day, and the Chronic Disease Risk Reduction Intake advises reducing intakes above 2,300 mg/day. No UL has been set.[1]
Sources
- [1]Dietary Reference Intakes for Sodium and Potassium: Report Highlights. National Academies of Sciences, Engineering, and Medicine, 2019. guideline
- [2]Sodium supplementation is not required to maintain serum sodium concentrations during an Ironman triathlon.. Br J Sports Med, 2006. RCT
- [3]Effects of oral salt supplementation on physical performance during a half-ironman: A randomized controlled trial.. Scand J Med Sci Sports, 2016. RCT
- [4]Fluid replacement during prolonged exercise: effects of water, saline, or no fluid.. Med Sci Sports Exerc, 1991. crossover-RCT
- [5]American College of Sports Medicine position stand. Exercise and fluid replacement.. Med Sci Sports Exerc, 2007. guideline
- [6]Oral salt supplementation during ultradistance exercise.. Clin J Sport Med, 2002. observational
- [7]Sodium replacement and fluid shifts during prolonged exercise in humans.. Eur J Appl Physiol, 2001. crossover-RCT
- [8]Sodium chloride (CID 5234): molecular weight. PubChem, NCBI, 2026. database
- [9]Sodium (CID 5360545): atomic weight. PubChem, NCBI, 2026. database
What changed
- First draft. Every evidence-row PMID checked with NCBI E-utilities (esummary + efetch abstract) and re-read in an independent adversarial pass.