Glycerol (glycerin)

Q: What does glycerol do before exercise?

Drunk with extra water, it holds more fluid in the body: about 7.7 mL per kg more than water alone in pooled studies.

Q: Does glycerol improve endurance?

Results are inconsistent. A 4-study pool found a 2.6% gain, and a 2024 pool found small gains in time to exhaustion and time trials but not total work.

Q: Is glycerol banned in sport?

WADA banned it from 2010 and removed it from the Prohibited List in 2018. Athletes should still check their own federation's current rules.

Q: What are the side effects?

Rarely nausea, stomach discomfort, light-headedness, dizziness or headache.

Q: What dose was studied?

The guideline protocol is 1.2 g per kg body weight in 26 mL per kg of fluid over 60 minutes, about 84 g for a 70 kg person. That is a research protocol, not a recommendation.

Also called glycerin, glycerine, glycerol hyperhydration, glycerol-induced hyperhydration.

Best grade C across 6 graded outcomes Other Last checked Oct 25, 2026

The short answer

From 10 sources

Drunk with extra water, glycerol helps the body keep more fluid: pooled studies show about 7.7 mL per kg more retained than water alone. Endurance gains are small and inconsistent, and a 2015 trial found plain salt retained more fluid. Side effects were rare: nausea, stomach discomfort, dizziness, headache. WADA removed it from its banned list in 2018.

Every graded outcome on this page

6 rows · line = participants

Grade CPlasma volume, hemoglobin and hematocrit vs fluid onlyPlasma volumen 54
Grade CFluid retention vs water aloneFluid retentionn 14
Grade CEndurance performance after pre-exercise hyperhydrationEndurance performancen 10
Grade DFluid retention: glycerol vs sodium vs waterFluid retentionn 17
Grade DFluid retention: salt plus glycerolFluid retentionn 15
Grade DEndurance performance vs water hyperhydrationEndurance performancen 4
3 more graded outcomes, in the evidence chapter

Key facts

What it is: Glycerol in a drink creates an osmotic pull that makes the body hold more fluid³
Fluid retention: 7.7 mL per kg body weight more than water-induced hyperhydration (pooled effect size 1.64, 14 comparisons)¹
Endurance performance: Inconsistent: +2.62% in a 4-study pool; pre-exercise hyperhydration of any agent gave small gains in time to exhaustion (g = 0.31) and time trial (g = 0.25) but not total work^1,8,5
Protocol studied: 1.2 g per kg body weight in 26 mL per kg of fluid over 60 minutes, 30 minutes before exercise (2010 review of the trials)³
Anti-doping status: Prohibited by WADA from 2010; removed from the Prohibited List in 2018^2,10

What it is

Glycerol (glycerin) is a sugar alcohol drunk with extra water before exercise to hold fluid; performance gains are small and inconsistent.

How it works

Proposed

Glycerol-containing drinks create an osmotic gradient in the blood that favors fluid retention, so extra body water of 1 L or more can be achieved. The effect on plasma volume is modest: glycerol added 3.3% more plasma volume than fluid alone in a 54-person pool.^3,2

Forms

Form

The form on this page
Form	Elemental %	Absorption (human data)	GI tolerance	Studied for
Glycerol powder or liquid mixed into a drink	Varies³Not applicable (dosed by grams of glycerol per kg body weight)	Ingested glycerol stays in the body water compartment and drives fluid retention; it adds 1 L or more of body water in many studies.³	Side effects are rare: nausea, stomach discomfort and light-headedness; a very small number of users reported dizziness and headache. Abdominal discomfort was low and not significantly different from salt or water drinks in two crossover trials.^3,5,7	Pre-exercise hyperhydration and rehydration

What the human research says

Human trials only, one row per outcome. The form line shows what each trial actually tested. Grades follow our evidence-grading policy.

Trial map

6 graded outcomes, largest study first

6 graded outcomes: 4 improved, 2 mixed. The largest, a 2013 meta-analysis of 54 people on plasma volume, hemoglobin and hematocrit vs fluid only, found an improvement.

By sizeTable

1Plasma volume, hemoglobin and hematocrit vs fluid only

Improved · Grade C · Meta-analysis, 54 people, 2013

Participants in 7 glycerol hyperhydration studies

Dose, result and source

Every graded outcome on this page, largest study first
Outcome	Found	People	Study	Who was studied
Plasma volume, hemoglobin and hematocrit vs fluid only	Improved	54	Grade C · Meta-analysis, 2013	Participants in 7 glycerol hyperhydration studies
Fluid retention: glycerol vs sodium vs water	Mixed	17	Grade D · Crossover RCT, 2015	Healthy young men
Fluid retention: salt plus glycerol	Improved	15	Grade D · Crossover RCT, 2018	Healthy young men
Fluid retention vs water alone	Improved	14	Grade C · Meta-analysis, 2007	Healthy participants in hyperhydration studies
Endurance performance after pre-exercise hyperhydration	Mixed	10	Grade C · Meta-analysis, 2024	Studies of oral hyperhydration before endurance exercise (agents included glycerol and sodium)
Endurance performance vs water hyperhydration	Improved	4	Grade D · Meta-analysis, 2007	Endurance-exercise studies

Every graded row

6 rows

Form tested

Showing 6 of 6 outcomes. Human trials only.

Grade CPlasma volume, hemoglobin and hematocrit vs fluid onlyPlasma volume+3.3% plasma volumeMeta-analysis · 5 studies
n 54 · 2013

Improved Plasma volume was 3.3% larger (95% CI 1.1 to 5.5%) with glycerol than fluid alone; hemoglobin was 0.2 g/dl lower (95% CI -0.3 to 0.0) and hematocrit unchanged.

Design: Meta-analysis, 5 studies, n = 54, 2013
Population: Participants in 7 glycerol hyperhydration studies
Form: Glycerol with fluid
Dose: Varied by trial
Duration: Single session
Source: Reference 2 · PubMed 24353192 (opens PubMed)

Grade CFluid retention vs water aloneFluid retention+7.7 mL/kg retainedMeta-analysis · 14 studies
n 14 · 2007

Improved Glycerol hyperhydration retained 7.7 +/- 2.8 mL per kg body weight more fluid than water hyperhydration (P < 0.01; pooled effect size 1.64 +/- 0.80).

Design: Meta-analysis, 14 studies, n = 14, 2007
Population: Healthy participants in hyperhydration studies
Form: Glycerol in fluid (about 1.1 g/kg body weight in about 24 mL/kg)
Dose: 1.1 +/- 0.2 g glycerol per kg body weight
Duration: Single session; measured about 136 minutes after onset
Source: Reference 1 · PubMed 17962713 (opens PubMed)

Grade CEndurance performance after pre-exercise hyperhydrationEndurance performanceSmall gain in some testsMeta-analysis · 10 studies
n 10 · 2024

Mixed Time to exhaustion improved (g = 0.31, 95% CI 0.13 to 0.50) and time trial improved (g = 0.25, 95% CI 0.002 to 0.51); total-work tasks did not (p = 0.120). Sodium gave lower body temperature than glycerol after the performance task (g = 0.80, p = 0.046).

Design: Meta-analysis, 10 studies, n = 10, 2024
Population: Studies of oral hyperhydration before endurance exercise (agents included glycerol and sodium)
Form: Hyperhydration with glycerol or sodium
Dose: Varied by trial
Duration: Single pre-exercise session
Source: Reference 8 · PubMed 38198662 (opens PubMed)

Grade DFluid retention: glycerol vs sodium vs waterFluid retentionLess than salt aloneCrossover RCT
n 17 · 2015

Mixed Sodium-induced hyperhydration retained more fluid than glycerol (1,144 vs 795 mL) and raised plasma volume more (11.9% vs 4.0%); abdominal discomfort did not differ.

Design: Crossover RCT, n = 17, 2015
Population: Healthy young men
Form: Glycerol (1.4 g per kg fat-free mass) in 30 mL/kg water
Dose: 1.4 g glycerol per kg fat-free mass
Duration: Single 3-hour session
Source: Reference 6 · PubMed 25494972 (opens PubMed)

Grade DFluid retention: salt plus glycerolFluid retentionCombination retained mostCrossover RCT
n 15 · 2018

Improved Salt plus glycerol retained 1,435 mL vs 729 mL with glycerol alone and 1,127 mL with salt alone; urine output was lowest with the combination; abdominal discomfort was low and did not differ.

Design: Crossover RCT, n = 15, 2018
Population: Healthy young men
Form: Glycerol (1.4 g per kg fat-free mass) with or without salt
Dose: 1.4 g glycerol per kg fat-free mass plus 7.5 g salt per liter
Duration: Single 3-hour session
Source: Reference 7 · PubMed 29140136 (opens PubMed)

Grade DEndurance performance vs water hyperhydrationEndurance performance+2.6% in 4 studiesMeta-analysis · 4 studies
n 4 · 2007

Improved Performance improved by 2.62% +/- 1.60% (P = 0.047; pooled effect size 0.35 +/- 0.13) across 4 studies; the authors called for more data before firm conclusions.

Design: Meta-analysis, 4 studies, n = 4, 2007
Population: Endurance-exercise studies
Form: Glycerol in fluid
Dose: About 1.1 g/kg body weight
Duration: Single pre-exercise session
Source: Reference 1 · PubMed 17962713 (opens PubMed)

What the numbers add up to

Each point is worked out from the data and the sources numbered on this page, with the arithmetic shown under it. It adds no new data and is not medical advice.

Retention is proven; performance is not

Pooled studies agree glycerol holds more fluid than water, but endurance results are mixed: gains of about 2.6% in 4 studies, benefits in time-to-exhaustion and time-trial tasks but not total work.^1,8,5

Salt does about as well

Salt alone retained 1,127 to 1,144 mL in two small trials, more than glycerol alone (729 to 795 mL).^6,7

Studied doses

Doses used in research, shown against the official limits. They describe the studies, not a recommendation for you.

Studied doses in research, not advice. These are amounts used in research, not personal advice. Your clinician or pharmacist can say what fits you.

Doses studied in human trials

Doses studied in human trials ranged from 0.125 g per kg body weight in 5 mL per kg of fluid during exercise to 1.4 g per kg fat-free mass before exercise, each given as a single session around exercise rather than daily intake.^3,6,7

Interactions and safety

Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.

What Glycerol meets

1 cited row

Medicines 0

No medicine rows in our sources.

Glycerol0 medicines · 1 supplement

Supplements and foods 1

Measured in a human study

Interactions

1 agent

Published interactions, grouped by kind
Agent	What the source says	Evidence
Other supplements1
Sodium (table salt)e.g. Salt added to the hyperhydration drink	In 15 men, salt plus glycerol retained 1,435 mL vs 729 mL with glycerol alone and 1,127 mL with salt alone. This is an additive hydration effect, not a safety interaction.⁷	RCT

Check with what you take

Kept on this device only

Add what you take. We list every interaction our evidence profiles cite between Glycerol and your picks, and between your picks.

Add a supplement or medicine

Most cited:

Add a supplement or medicine you take to check it against Glycerol.

Starting from one medicine? The interaction checker rates how serious each pair is, on a curated list of 19 entries for 11 medicines. This cabinet has no severity rating: it lists every interaction row our supplement pages cite.

Who should be careful

5 groups

Stomach upset, dizziness or headache: Nausea, gastrointestinal discomfort, light-headedness, dizziness and headache have been reported, though rarely and in a very small number of users.^3,5
Large fluid loads: The protocols had people drink about 24 to 30 mL of fluid per kg within an hour. No cited abstract studied people with heart, kidney or blood-pressure conditions or fluid restrictions, so anyone with those should check with a clinician first; this is a precaution, not a trial finding.^3,6,7
Women and elite athletes: The trials cited enrolled healthy young men, and the 2024 meta-analysis notes few elite or female athletes were represented.^6,7,8
Drug-tested athletes: Glycerol was banned by WADA from 2010 and removed from the Prohibited List in 2018. Urinary excretion may be detectable above about 0.032 g per kg lean body mass, so athletes under testing should confirm current rules with their federation.^2,10,4
Pregnancy, breastfeeding and children: The cited trials and pooled analyses enrolled healthy adults, mostly young men, and none tested glycerol hyperhydration in pregnancy, breastfeeding or children, so its safety in these groups is unknown.^6,7,8

How to read the label

What to check on the Supplement Facts panel.

How to read the label

2 checks

Label dose vs studied dose

The guideline protocol is 1.2 g per kg body weight, which is about 84 g for a 70 kg person (1.2 x 70), taken in 26 mL per kg of fluid. Compare a product's grams of glycerol per serving with that amount; small servings supply a fraction of what the trials tested.³

Regulatory status

In the United States, glycerin is listed as generally recognized as safe as a food substance when used in accordance with good manufacturing practice. That regulation covers food use, not any performance claim. WADA removed glycerol from the Prohibited List in 2018.^9,10

Frequently asked questions

Short answers to common questions; the numbers link to the sources below.

Common questions

5 answers

What does glycerol do before exercise?

Drunk with extra water, it holds more fluid in the body: about 7.7 mL per kg more than water alone in pooled studies.¹

Does glycerol improve endurance?

Results are inconsistent. A 4-study pool found a 2.6% gain, and a 2024 pool found small gains in time to exhaustion and time trials but not total work.^1,8,5

Is glycerol banned in sport?

WADA banned it from 2010 and removed it from the Prohibited List in 2018. Athletes should still check their own federation's current rules.^2,10

What are the side effects?

Rarely nausea, stomach discomfort, light-headedness, dizziness or headache.^3,5

What dose was studied?

The guideline protocol is 1.2 g per kg body weight in 26 mL per kg of fluid over 60 minutes, about 84 g for a 70 kg person. That is a research protocol, not a recommendation.³

Sources

10 sources: trial abstracts, NIH fact sheets and reference databases. Numbers in the text link here.

Sources cited on this page

10 sources

1A meta-analysis of the effects of glycerol-induced hyperhydration on fluid retention and endurance performance.Meta-analysis Int J Sport Nutr Exerc Metab, 2007 · PMID 17962713
2Meta-analysis: Effects of glycerol administration on plasma volume, haemoglobin, and haematocrit.Meta-analysis Drug Test Anal, 2013 · PMID 24353192
3Guidelines for glycerol use in hyperhydration and rehydration associated with exercise.Review Sports Med, 2010 · PMID 20092365
4Glycerol use in hyperhydration and rehydration: scientific update.Review Med Sport Sci, 2012 · PMID 23075560
5Physiological and performance effects of glycerol hyperhydration and rehydration.Review Nutr Rev, 2009 · PMID 19941615
6Sodium-induced hyperhydration decreases urine output and improves fluid balance compared with glycerol- and water-induced hyperhydration.Crossover RCT Appl Physiol Nutr Metab, 2015 · PMID 25494972
7Salt + Glycerol-Induced Hyperhydration Enhances Fluid Retention More Than Salt- or Glycerol-Induced Hyperhydration.Crossover RCT Int J Sport Nutr Exerc Metab, 2018 · PMID 29140136
8The effect of pre-exercise oral hyperhydration on endurance exercise performance, heart rate, and thermoregulation: a meta-analytical review.Meta-analysis Appl Physiol Nutr Metab, 2024 · PMID 38198662
921 CFR 182.1320 Glycerin (Substances Generally Recognized as Safe)Guideline Electronic Code of Federal Regulations, 2026 · ecfr.gov
102018 Prohibited List: Summary of Major ChangesFact sheet U.S. Anti-Doping Agency, 2017 · usada.org

What changed

Every dated change to this page: what changed, who made it and why.

Change log

2 entries

Dated changes to this page
Date	Change	Who and why
Oct 25, 2026safety	Adversarial review: every row re-read against its abstract (numbers match). Added the missing pregnancy, breastfeeding and children note; protocol key fact reworded to match the 2010 review ("over 60 minutes, 30 minutes before exercise"). USADA 2018 list summary and 21 CFR 182.1320 re-opened and confirmed.	Writer: Kymata Health EditorialTrigger: adversarial review
Oct 16, 2026all	Initial editorial evidence review. Every PMID checked against NCBI E-utilities esummary (title, year, journal) and each cited abstract read; numbers taken from the abstracts only. Meta-analysis rows show the number of pooled comparisons in n where the abstract gives no participant total (flagged in each row). Rows for sodium and for salt plus glycerol show that salt alone matched or beat glycerol. WADA status from the USADA 2018 list summary; GRAS line from 21 CFR 182.1320. Funding is not stated in the abstracts except the 2024 meta-analysis (no competing interests).	Writer: Kymata Health EditorialTrigger: new page

Supplement & Nutrient Encyclopedia. Educational information only; it is not medical advice and does not replace a clinician. Dietary supplements are not intended to diagnose, treat, cure or prevent any disease. Statements about supplements have not been evaluated by the FDA.

Glycerol (glycerin)

Medicines 0

Supplements and foods 1

Electrolytes and sodiumElectrolytes and sodium page