Creatine monohydrate is the most common form of creatine, and, unless otherwise stated, the default form of creatine used in most studies.[1] It has high intestinal absorption, with bioavailability of approximately 99% at standard doses of 5–10 g.[2][3] That said, there is evidence to suggest that high acute doses (greater than 10g) of creatine monohydrate can saturate intestinal uptake, lowering absorption and increasing fecal secretion.[4]
This basic form of creatine comes in two variants: creatine anhydrous and micronized creatine monohydrate.
Creatine anhydrous (anhydrous coming from the Greek “an-” meaning “without”, and “hydor” meaning “water”) is just creatine without the monohydrate. Creatine anhydrous is converted to creatine monohydrate when exposed to water.[5][6] Because it does not contain monohydrate, creatine anhydrous is 100% creatine by weight, whereas creatine monohydrate is 88% creatine and 12% monohydrate by weight.
Micronized creatine monohydrate is creatine monohydrate that undergoes a mechanical process that reduces the particle size and increases the water solubility of creatine.
Other creatine formulations include:
- Creatine hydrochloride (Creatine HCl): This form is characterized by the creatine molecules being bound with hydrochloric acid. Creatine HCl is touted to require a lower dosage. However, this claim has not been scientifically proven and seems unlikely, since the stomach has an abundance of HCl anyway, and creatine will separate from HCl in the stomach. Thus, both creatine HCl and creatine monohydrate form free creatine in the stomach.
- Liquid creatine: This form has been found to be less effective than creatine monohydrate.[7] The reduced effect is likely due to the passive breakdown of creatine over a period of days into creatinine, which occurs when creatine is suspended in solution.[8] This is not an issue for people preparing a creatine solution at home, since it takes a few days for creatine to start degrading into creatinine.
- Buffered creatine (Kre-Alkalyn): This form of creatine has a higher pH level than creatine monohydrate. This is accomplished by adding alkaline powder to creatine. Buffered creatine is touted to enhance the effects of creatine monohydrate. However, this claim has not been scientifically proven. In fact, a 2012 study comparing buffered creatine to creatine monohydrate in 36 resistance-trained individuals found no significant differences between the two with regard to the accumulation of creatine in muscle tissue, training adaptations, or adverse effects.[9]
- Creatine ethyl ester: This is an esterified form of creatine monohydrate that has been found to be less effective than creatine monohydrate for increasing muscle creatine levels and enhancing resistance training adaptations.[10]
- Magnesium-chelated creatine: In this form of creatine, magnesium ions are attached to the creatine molecules. Limited research suggests that this form of creatine may have the same ergogenic effects as creatine monohydrate.[11]
- Creatine nitrate: In this form of creatine, a nitrate (NO3−) ion is attached to a creatine molecule. Despite creatine nitrate being more soluble in water, it doesn't appear to enhance athletic performance more than creatine monohydrate.[12]