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Glycerol (Hyperhydration)

Also known as Glycerin · Glycerine · Glycerol

Written by enwyReviewed 15 Jul 20261 sources0 comments

An osmotic agent used to expand body-fluid stores before exercise in the heat. When co-ingested with a large fluid load it increases fluid retention and can modestly improve endurance and thermoregulation. Once WADA-banned as a plasma expander, now permitted.

01 Overview

Glycerol is a sugar alcohol that, taken with a large volume of fluid, raises plasma osmolality and draws water into body-fluid compartments, increasing total retained fluid. This 'hyperhydration' can lower cardiovascular and thermal strain during prolonged exercise in the heat.

Controlled trials show increased fluid retention and modest endurance and thermoregulatory benefits in hot conditions, though results vary with protocol. Notably, glycerol was on the WADA prohibited list until 2018 as a potential plasma expander/masking agent; it has since been removed and is currently permitted.

02 Mechanism

Acts as an osmotic agent that, co-ingested with fluid, raises plasma osmolality and increases water retention across body compartments, expanding fluid reserves before heat stress.

03 Dosing

Tier	Dose	Route	Notes
Common	1–1.5 g/kg	Oral	~1.2 g/kg body mass with ~25-30 mL/kg fluid, 1-2 h before exercise in the heat.

04 Effects

Effect	Magnitude	Evidence
Increased fluid retention (hyperhydration)Reliably increases total body water retained before exercise when co-ingested with a large fluid load.	Greater retained fluid vs water alone	Clinical
Improved endurance/thermoregulation in heatModest improvements in prolonged exercise and thermal strain in hot conditions.	Modest, protocol-dependent	Clinical

05 Side effects

Effect	Severity	Frequency	Evidence	Countermeasures
Gastrointestinal upset and nauseaNausea, bloating and GI discomfort from the osmotic load and large fluid volume.	Mild	Frequent	Clinical
Headache and weight gainTransient headache and acute body-mass increase from fluid retention.	Mild	Frequent	Observational

06 Legal status

United States

Dietary supplement / GRAS

Removed from the WADA prohibited list in 2018; currently permitted. · as of Jan 2026

07 References

Glycerol hyperhydration and endurance performance in the heatSports Med (search)

08 Discussion0 comments

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This page is reference information, not medical advice. Doses and protocols are documented as they appear in the clinical literature and in practice — describing them is not a recommendation to use them. Countermeasures listed here are not a substitute for a physician. Legal status varies by jurisdiction and changes.