Glycerol
Glycerol binds water in the body. That effect has been shown in hyperhydration at around 1.2 grams per kilo of body weight, so about 80 grams for someone weighing 70 kilos, measured as plasma volume. At the 1 to 4 grams found in pre-workouts, human research is missing.
What the research shows
Shown, with a clear condition or a limited scope.
Glycerol has been studied repeatedly in humans for fluid retention. Goulet (2007) pooled fourteen comparisons and saw more than 7 ml of extra fluid retained per kilo of body weight compared with water alone, plus a 2.6 percent gain in endurance performance across four performance studies. Koehler (2013) arrived at 3.3 percent more plasma volume across seven studies. McCubbin (2024) found a small to moderate benefit on time to exhaustion across ten publications. All three meta-analyses come from universities with no manufacturer involved. The limitation lies in the application and the amount: the research is about endurance work and heat, at around 1.2 grams per kilo of body weight, roughly 85 grams for someone weighing 70 kilos. Muscle pump and strength training were never examined.
Who it makes sense for: Endurance athletes who want to hyperhydrate before a long effort in the heat and therefore end up at tens of grams. At the 1 to 4 grams from a pre-workout there is no research showing an effect.
How we weigh evidenceClinical dosage
Origin
Natural & syntheticGlycerol (glycerine) is a natural byproduct of fat digestion and occurs in all animal and plant fats. In supplements usually derived from vegetable oils.
Safety
Glycerol is safe at supplement doses. Large amounts can cause stomach upset and nausea. Note the gap between research and practice: the studies use tens of grams for endurance sport, and a meta-analysis calls the effect on plasma volume limited even there.
For comparison
Glycerol is in your toothpaste, soap, and many processed foods as a humectant. It's one of the safest supplements that exist.
Dosage by weight and gender
The effective glycerol dose for hyperhydration is 1-1.5g per kg body weight, taken 60-90 minutes before training with 25-30ml of water per gram of glycerol (van Rosendal et al., 2010). For someone weighing 70kg that's 70-105g, for 90kg it's 90-135g. Pre-workouts use much lower doses (2-5g) for a pump effect, not full hyperhydration. There are no differences in effect between men and women.
Frequently asked questions
What is glycerol?
Glycerol is a sugar alcohol that attracts and retains water. In pre-workouts it creates a fuller pump because your muscles hold more water. It's also widely used as a food additive (E422).
Is glycerol dangerous?
No, glycerol is one of the safest substances around. It's used as a food additive in countless products, from toothpaste to pastries. At very high doses you might experience mild headache or nausea from the water retention.
How much glycerol per day?
Pre-workouts typically contain 2-5g glycerol per serving for a pump effect. That's enough for a noticeable difference. Drink plenty of water with it, otherwise it won't work optimally.
Scientific sources
The clinical dosages on this page are based on peer-reviewed research.
- Meta-analysis: Effects of glycerol administration on plasma volume, haemoglobin, and haematocritKoehler K et al. (2013)
- Guidelines for glycerol use in hyperhydration and rehydration associated with exercisevan Rosendal SP et al. (2010)
- A meta-analysis of the effects of glycerol-induced hyperhydration on fluid retention and endurance performanceGoulet ED et al. (2007)
- The effect of pre-exercise oral hyperhydration on endurance exercise performance, heart rate, and thermoregulation: a meta-analytical reviewMcCubbin Aj et al. (2024)
Pre-workouts with Glycerol
No products found with this ingredient
We keep the dosages and values on this page as accurate as possible based on selected studies. New research may change these values. Nothing on this page is medical advice. If you have any doubts, always consult a doctor.