NutriDex

The Supplement Research Compendium
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Glycerol

Osmotic hyperhydration agent for endurance in the heat.

Moderate evidence ⚡Performance

✚ Updated · How we grade evidence

Evidence tier
Moderate
Research weight
Citations
7 verified / 7
Classification
Performance
❝
What the evidence says. Graded moderate: glycerol reliably increases fluid retention and plasma volume, but the downstream performance gain is small (~2–3%) and inconsistent — several well-controlled RCTs in the heat found no improvement in time-trial performance. (Moderate evidence: Several controlled trials; effects real but modest or context-dependent.)

What is Glycerol?

Glycerol is a performance supplement used for pre-exercise hyperhydration. NutriDex grades the human evidence as Moderate. Glycerol is a simple sugar-alcohol used as an osmotic 'hyperhydration' aid. Taken with a large fluid load before exercise, it draws water into the body's compartments, reliably boosting fluid retention (a 2007 meta-analysis found ~7.7 mL/kg more retained than water alone) and expanding plasma volume by roughly 3–10%. The point is to delay dehydration during prolonged exercise in the heat. The performance payoff, however, is modest and uneven: meta-analyses estimate around a 2–3% improvement in endurance, and a 2024 review found only small-to-moderate gains in time-to-exhaustion. Notably, several controlled trials — including a 5-km time-trial in 30°C heat — found better hydration but no actual performance benefit. Glycerol was removed from the WADA prohibited list in 2018 after its masking effect was judged minimal. It is best viewed as a situational tool for hot-weather endurance, not a general ergogenic.

Purported Benefits

✓Pre-exercise hyperhydration
✓Greater fluid retention
✓Expanded plasma volume
✓Aid endurance in the heat
✓Faster rehydration

Evidence by outcome

The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.

OutcomeEvidenceEffectStudies
Greater fluid retention & hyperhydrationMeta-analysis: ~7.7 mL/kg more fluid retained vs water; RCT confirmed +846 mL retention. Hydration effect is robust. Strong ↑ benefit · moderate 2
Expanded plasma volumeTrials show plasma volume expansion of roughly 3-10%; mechanistically consistent across reviews. Moderate ↑ benefit · moderate 2
Aid endurance performance in the heatMeta-analyses show small ~2-3% endurance gain, but several RCTs (incl. 5-km in 30°C) found better hydration yet no performance benefit. Mixed ↔ mixed · small 3

Dosing & Compounds

Typical Dose
1.0–1.2 g/kg body weight in ~25 mL/kg fluid, taken over ~60 min and finishing ~30 min before exercise.
Active Compounds
Glycerol (1,2,3-propanetriol)

Safety & Cautions

Generally well tolerated, but the required large fluid load and osmotic action commonly cause nausea, bloating, GI upset, headache and dizziness, and some users feel an urgent need to urinate. The fluid retention can transiently raise body weight (~1–1.5 kg), which may matter in weight-class sports. Avoid in people with kidney disease, heart failure or any condition where fluid overload is dangerous, and use caution in those prone to migraines. No major drug interactions are established, but glycerol can theoretically blunt the action of diuretics; it was banned by WADA as a masking agent until 2018. Educational only — always check with your doctor or pharmacist before combining Glycerol with any medicine.

Key Studies

Meta-analysis Pre-exercise oral hyperhydration meta-analysis 2024 ✓ PubMed
Small-to-moderate gains in time-to-exhaustion and time-trial, but not total-work tasks; sodium lowered post-task body temperature vs glycerol.
Systematic review Jardine 2023 ✓ Full text
Systematic review (33 studies, 403 subjects): hyperhydration improved time-to-exhaustion in 5 of 7 constant-load trials; effects on other tasks inconsistent.
Meta-analysis Goulet 2007 ✓ PubMed
Meta-analysis: glycerol retained ~7.7 mL/kg more fluid than water and improved endurance performance by 2.62% ± 1.60%.
RCT Jolicoeur Desroches 2023 ✓ PubMed
RCT crossover: greater fluid retention (846 mL) and plasma volume (+10.1%), but no improvement in 5-km running time-trial in 30°C heat.
RCT Herrera-Amante 2025 ✓ Full text
Crossover RCT (30 runners): 1.2 g/kg glycerol cut caloric cost 2.25%, heart rate 2.1 bpm and RPE 18% despite ~1.4 kg added body mass.
Review van Rosendal 2010 ✓ PubMed
Evidence-based guidelines: 1.2 g/kg glycerol in 26 mL/kg fluid over 60 min, 30 min pre-exercise, for hyperhydration.
Review van Rosendal 2009 ✓ PubMed
Review: glycerol raised plasma volume, sweat rate and lowered core temperature, but documented performance benefits remained inconsistent.
7 sources cited · 7 verified Search all studies on PubMed ↗

Common questions about Glycerol

What is Glycerol used for?

Glycerol is most often taken for Pre-exercise hyperhydration, Greater fluid retention, Expanded plasma volume, Aid endurance in the heat. Osmotic hyperhydration agent for endurance in the heat.

Does Glycerol work — what does the evidence say?

Moderate evidence. Several controlled trials; effects real but modest or context-dependent. Glycerol is a simple sugar-alcohol used as an osmotic 'hyperhydration' aid. Taken with a large fluid load before exercise, it draws water into the body's compartments, reliably boosting fluid retention (a 2007 meta-analysis found ~7.7 mL/kg more retained than water alone) and expanding plasma volume by roughly 3–10%. The point is to delay dehydration during prolonged exercise in the heat. The performance payoff, however, is modest and uneven: meta-analyses estimate around a 2–3% improvement in endurance, and a 2024 review found only small-to-moderate gains in time-to-exhaustion. Notably, several controlled trials — including a 5-km time-trial in 30°C heat — found better hydration but no actual performance benefit. Glycerol was removed from the WADA prohibited list in 2018 after its masking effect was judged minimal. It is best viewed as a situational tool for hot-weather endurance, not a general ergogenic.

What is the typical dose of Glycerol?

1.0–1.2 g/kg body weight in ~25 mL/kg fluid, taken over ~60 min and finishing ~30 min before exercise.

Is Glycerol safe? Any cautions or side effects?

Generally well tolerated, but the required large fluid load and osmotic action commonly cause nausea, bloating, GI upset, headache and dizziness, and some users feel an urgent need to urinate. The fluid retention can transiently raise body weight (~1–1.5 kg), which may matter in weight-class sports. Avoid in people with kidney disease, heart failure or any condition where fluid overload is dangerous, and use caution in those prone to migraines. No major drug interactions are established, but glycerol can theoretically blunt the action of diuretics; it was banned by WADA as a masking agent until 2018.

How many studies support Glycerol?

NutriDex cites 7 sources for Glycerol, graded "Moderate".

Cite this page
APA

Peh, D. (2026). Glycerol: Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/glycerol

BibTeX
@misc{nutridex_glycerol,
  author       = {Peh, Daryl},
  title        = {Glycerol: Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/glycerol},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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