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Limited evidencePhysical performance

Guanidinoacetic Acid (GAA)

The body's direct precursor to creatine. It does raise tissue creatine, but it also raises homocysteine, and it has never been shown to beat simply taking creatine.

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What the science says

  • Raises muscle and brain creatine Limited evidence

    A randomised superiority pilot trial in healthy men found guanidinoacetic acid increased muscle and brain creatine more than creatine monohydrate over several weeks. It was a pilot with very few participants.

  • Raises homocysteine Moderate evidence

    A randomised, double-blind trial comparing guanidinoacetic acid plus creatine with creatine alone found the GAA arm developed higher plasma homocysteine, an unwanted change, without a clear performance advantage.

  • No performance case over creatine Limited evidence

    No trial has shown guanidinoacetic acid outperforms creatine monohydrate for exercise performance, and human data cover only weeks to a few months.

Dosage & safety

Studied doseTrials used 1.2–3 g/day for 4–8 weeks, sometimes with creatine and with B vitamins intended to blunt the homocysteine rise.
SafetyIt raises homocysteine; co-supplementation with folate and B12 is proposed but not proven to solve this. Long-term safety is unknown and it is not an authorised novel food in some jurisdictions. Avoid in pregnancy and in kidney disease.

How to take it

TimingTiming does not matter.
With food?Take it with food.
Worth knowingIf you use it at all, have homocysteine measured before and after, because a rise is the documented effect and not a theoretical one.

Interactions

With other supplements

  • folate and vitamin B12

    They are co-dosed to blunt the homocysteine rise GAA causes, though this has not been shown to work. do not treat the B vitamins as proof the homocysteine problem is solved

  • creatine

    GAA is the precursor to creatine, so the two overlap in what they do. there is no reason to run both when plain creatine is better studied

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Is guanidinoacetic acid (GAA) better than creatine?

No trial has shown guanidinoacetic acid (GAA) outperforms creatine monohydrate for exercise performance. A small pilot trial found GAA raised muscle and brain creatine more than creatine, but the evidence is limited.

Does GAA raise homocysteine?

Yes, a double-blind randomised trial found guanidinoacetic acid raised plasma homocysteine compared with creatine alone, without a clear performance advantage. If you use GAA, have homocysteine measured before and after.

Do B vitamins prevent the homocysteine rise from GAA?

Folate and vitamin B12 are often co-dosed with guanidinoacetic acid to blunt its homocysteine rise, but this has not been shown to work. Do not treat added B vitamins as proof the GAA homocysteine problem is solved.

How much guanidinoacetic acid do studies use?

Guanidinoacetic acid trials used 1.2–3 g/day for 4–8 weeks. Long-term safety of GAA is unknown, and it should be avoided in pregnancy and kidney disease.

Scientific references

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