Years ago, one of the biggest supplement scams was a ready-to-drink creatine serum. This was before it was widely known that creatine does not remain stable in liquid for long periods of time. When creatine hits water, it begins transforming into inert creatinine. That shouldn’t keep you from pre-mixing your own post-workout creatine concoctions, though.
Research shows that after eighth hours there is no measurable degradation of the supplement. Even after three days of immersion, 90 percent of the creatine is still active.
Cooler temperatures seems to slow the transition from creatine to creatinine, so keeping your homemade muscle-building cocktail in the refrigerator will help it last even longer.