Creatine monohydrate

What is creatine monohydrate, and why is it considered the reference form?

Creatine monohydrate is the crystalline form of creatine containing one water molecule. According to the ISSN 2021 paper, it has been the most studied and used form in creatine supplements since the early 1990s; it was used in the first studies that determined bioavailability, amount and effect on muscle creatine stores. About 99% of orally taken monohydrate is either retained by tissue or excreted in urine as creatine. ^[2] The ISSN 2017 paper relays the same finding, stating that absorption is about 100%, and says that claims that different forms degrade less or provide more muscle uptake are “unsubstantiated for now.” ^[1]

The IOC’s 2018 consensus statement also uses the wording “creatine (in the form of creatine monohydrate)” among supplements with sufficient evidence for a contribution to performance. ^[6]

What are the other creatine forms, and what does the evidence say?

The 2011 review by Jäger and colleagues also concludes that “there is little or no evidence that novel forms of creatine are more effective or safer than monohydrate”; it also states that the safety, efficacy and regulatory status of monohydrate are clear in almost every global market, while for other forms this is more uncertain. ^[3] According to the review, outside Japan, monohydrate is the only creatine form officially approved or accepted in major markets such as the US, the European Union, Canada and South Korea; this is a 2011 finding. ^[3]

What was found for the buffered and ethyl ester forms?

Buffered form (Jagim et al., 2012)

The study included 36 young people performing resistance training (mean age 20.2) who were divided double-blind into three groups: monohydrate (4 × 5 g per day for 7 days, then 5 g per day for 21 days), the buffered form at the amount recommended by the manufacturer (1.5 g per day for 28 days), or the buffered form at the same loading and maintenance amounts as monohydrate. Muscle free creatine content (in a subgroup of 25 people) increased over time in all groups and there was no significant difference between groups (p = 0.46); in the pairwise comparison between the low-dose buffered group and the monohydrate group, the increase tended to be greater with monohydrate (p = 0.053). No group-by-time interaction was found for body mass, lean mass, fat mass, total body water, bench press and leg press 1RM strength and Wingate anaerobic power measurements; there was also no evidence that the buffered form caused fewer side effects. ^[4]

The study was funded by a research grant from a creatine monohydrate manufacturer; the authors state that the results were collected and interpreted independently. ^[4] The duration is four weeks and the participants were young, trained individuals; the results cannot be generalized to longer periods or other groups.

Ethyl ester (Spillane et al., 2009)

Thirty untrained men were randomly assigned to placebo, monohydrate or ethyl ester groups during 7 weeks of resistance training; 0.30 g per kg of lean mass (about 20 g/day) was given for 5 days, followed by 0.075 g/kg (about 5 g/day) for 42 days. Serum creatine was higher in the placebo and monohydrate groups than ethyl ester; serum creatinine was higher in the ethyl ester group than placebo and monohydrate. Muscle total creatine was higher in both the monohydrate and ethyl ester groups than placebo, with no difference between the two forms. Body composition, muscle mass, strength and power variables changed over time but no difference emerged between groups. The authors concluded that ethyl ester was not more effective than monohydrate and that improvements were most likely due to the training program. ^[5] The products used in the study belong to commercial manufacturers; the authors reported no conflict of interest. ^[5]

The review by Jäger relays in vitro findings showing that ethyl ester is not converted to creatine in plasma and under physiological conditions is mainly converted to creatinine. ^[3]

How much of the powder is creatine, by form?

Table 1 of Jäger and colleagues shows how much creatine the forms contain by weight. Creatine monohydrate has the highest proportion apart from anhydrous creatine. ^{[3] [2]}

The proportions are taken from the review; the last column is an arithmetic calculation from these proportions. This means that when the price of different forms is compared per “gram of creatine” rather than per “gram of powder,” it may turn out differently; however, this guide recommends no price or product. The ISSN 2021 paper states that other forms contain less creatine per gram and therefore showed less physiological effect in most studies; if there is a performance difference, it may come from other ingredients bound to or taken with creatine. ^[2]

How is the label read? What does each piece of information show?

A label has two separate pieces of information: the name of the form and the amount of creatine per serving. The name of the form determines the creatine proportion of the powder (table above); creatine in “serum” and drinks is only at the milligram level. ^[2] “Superior form” claims on a label are, according to the ISSN, not clinically supported. ^[1]

In blend products (carbohydrate, caffeine or other ingredients together with creatine), a reported performance difference may, according to ISSN 2021, come not from creatine itself but from the ingredients present with it. ^[2] Because the studies conducted compared monohydrate alone, separate evidence is needed for the effect of blend products.

Are there differences in product quality and purity?

The purity of creatine monohydrate may vary by manufacturing method. The ISSN 2021 paper relays that with some manufacturing methods and sources, up to 5.4% of dicyandiamide, dihydrotriazine, creatinine, dimethyl sulfate, thiourea and heavy metals have been detected; it states that health effects are unknown and that dihydrotriazine has raised the most concern. ^[2] Product contamination and doping risk for athletes are covered in detail on the safety page. This guide does not identify a product or brand that guarantees purity or source.

Does creatine degrade in liquid?

Creatine monohydrate powder is stable; in aqueous solution it converts to creatinine over time, and this rate rises as pH falls and temperature increases. According to ISSN 2017, in a solution stored at 25 °C for 3 days, creatine converts to creatinine at rates of 4% (pH 5.5), 12% (pH 4.5) and 21% (pH 3.5). ^[1] ISSN 2017 gives the conversion of creatine to creatinine as the main reason why creatine is sold in solid form; it also states that conversion during digestion is minimal. ^[1]

This guide does not recommend a personal dose, product or brand.