Glycerol

A hyperhydration agent that expands fluid volume for hot-weather endurance — real but niche.

Overall grade: Grade C
Last revised: Jul 10, 2026; 2
graded outcomes: 0
references listed

A structured monograph in Prometheus's bundled library. Its grades are the monograph's own reading of the evidence, not a peer-reviewed review.

1 at grade B · 1 at grade C — 2 graded rows

What is known

Each outcome with its grade (how strong the evidence is, A to D), the size of the effect where the entry records one, and how often studies agree.

Outcome	Grade	Effect size	Agreement
Fluid retentionReliable osmotic effect	Evidence grade B	Moderate	high
Endurance in heatVia hyperhydration	Evidence grade C	Small	mixed

Fluid retentionEvidence grade B
Reliable osmotic effect
Moderatehigh
Endurance in heatEvidence grade C
Via hyperhydration
Smallmixed

What is uncertain

Read off the same rows as above. Nothing here is added that the entry does not itself record.

Thin evidence: Endurance in heat (grade C).

Interactions

Documented pairings with supplements and medicines. A medicine on this list is a conversation for whoever prescribes it.

ElectrolytesWorks together
Paired for hyperhydration protocols.

The evidence in words

What it is

Glycerol is a sugar alcohol used to hyperhydrate before endurance events in the heat.

How it works

It osmotically holds water, expanding blood and tissue fluid volume to buffer dehydration and thermal strain.

What the evidence shows

Reasonable evidence that glycerol hyperhydration improves fluid retention and can aid endurance performance in the heat; effects in cool conditions are minimal. GI upset and its former banned status (now permitted) are considerations.

How to use it

~1–1.2 g/kg with substantial fluid before hot endurance events; trial in training.

Safety & interactions

GI upset, headache; caution with kidney issues. electrolytes — Paired for hyperhydration protocols.

Bottom line

A legitimate hot-weather hyperhydration tool for endurance athletes; pointless in the cold. Practice it first.

How it is used

As the entry records it, from the studies it summarises. Not a recommendation for you — doses that suit a trial population may not suit you.

Pre-event: ~1–1.2 g/kg with fluid, hot conditions.

Entries that share this one's tags or conditions.

Glycerol for Endurance in heatEvidence grade C — Via hyperhydrationEvidence grade C
Glycerol for Fluid retentionEvidence grade B — Reliable osmotic effectEvidence grade B
Glycerol: dosage and how to take it~1–1.2 g/kg with fluid, hot conditions.Evidence grade C
Glycerol: side effects, safety & interactionsGI upset, headache; caution with kidney issues.Evidence grade C

Sources

This entry lists no references of its own.

Last revised Jul 10, 2026. A grade is this entry's reading of the evidence, not medical advice.