Creatine ethyl ester (CEE) is creatine with an ethyl group attached, sold on the claim that it is absorbed better than monohydrate. Measured, it did the reverse: in a seven-week trial of 30 men (Spillane et al., 2009), serum creatinine roughly tripled on CEE within six days, serum creatine ran lower than on monohydrate, and muscle creatine did no better. Laboratory work found it breaks down at gut pH. Monohydrate wins.
CEE is the clearest case in the creatine aisle of a form that was sold on a mechanism and then measured. The mechanism sounded like pharmacology. The measurement found a supplement that mostly turns into creatinine, the breakdown product the body excretes. What follows is the claim, the trial, the chemistry and the limits, in that order.
What is creatine ethyl ester?
It is creatine with an ethyl group bonded to its acid end, an ester. Esterification makes the molecule less water-loving, and the pitch was that a more fat-soluble creatine would slip into cells without needing the creatine transporter. Writing in 2009, the authors of the only head-to-head trial noted that there were no published data to substantiate that allegation. As the bare ester it is 82.4% creatine by weight, against 87.9% for monohydrate, by the 2011 review of novel creatine forms.
The trial's capsules held it as the hydrochloride salt — 700 mg capsules, checked by NMR as pure creatine ethyl ester hydrochloride. Our arithmetic on the formula weights puts that salt at about 67% creatine, so a gram of it carries roughly a quarter less creatine than a gram of monohydrate before anything has happened to it in the body. The bare-ester figure is the one in the table on creatine HCl vs monohydrate; the salt is what was actually sold and swallowed.
Is creatine ethyl ester better than creatine monohydrate?
No. Spillane and colleagues (2009) randomised 30 untrained young men to CEE, monohydrate or placebo for seven weeks of resistance training four days a week, at about 20 g a day for five days and then about 5 g a day. Serum creatine was lower on CEE than on monohydrate. Serum creatinine, the breakdown product, was higher on CEE than in either other group, with significant elevations on CEE at days 6, 27 and 48. The training measures improved alike in all three groups, placebo included.
The authors concluded that CEE “was not as effective at increasing serum and muscle creatine levels” as monohydrate, and put the training improvements down to the training itself. The muscle half of that sentence needs a caveat the paper forces on its reader. Its abstract and the section reporting its data put total muscle creatine above placebo on both creatine forms, with no difference between the two; its discussion says CEE did not beat placebo; its conclusion says neither form raised muscle creatine significantly. A paper that disagrees with itself on its central muscle measurement is a paper to read for its blood numbers, whose comparison of the two creatine forms agrees in every section.
Those blood numbers are not subtle. On CEE, serum creatinine roughly tripled within six days, from an average of 0.95 to 2.68 mg/dL. On monohydrate it stayed inside the 0.8–1.3 mg/dL normal range the authors quote. A supplement sold as the better-absorbed creatine was, on the evidence of the blood, largely being turned into creatinine.
| What was claimed | What was measured | Source |
|---|---|---|
| Higher bioavailability than monohydrate | Serum creatine lower on CEE than on monohydrate; serum creatinine roughly tripled by day 6 | Spillane et al., 2009 |
| Bypasses the creatine transporter into muscle | Muscle creatine no higher than on monohydrate; whether it beat placebo, the paper's own sections disagree | Spillane et al., 2009 |
| Reaches the body as creatine | Folds into creatinine without any enzyme; the same group's plasma work found it mostly converted to creatinine | Giese and Lecher, 2009; the 2011 review |
| A superior form of creatine | Calculated half-life of 22 days at pH 1, but 2 minutes at pH 7 and 56 seconds at pH 7.4 | Katseres et al., 2009 |
Does creatine ethyl ester turn into creatinine?
Mostly, and quickly once it leaves the stomach. Katseres and colleagues (2009) measured its breakdown rate between pH 1.6 and 7.0 and calculated its half-life by pH: 22 days at pH 1, 18 hours at pH 4, 2 minutes at pH 7 and 56 seconds at pH 7.4, the pH of blood. Giese and Lecher (2009) identified what it becomes: creatinine, formed as the molecule folds in on itself without any enzyme's help. The 2011 review of novel forms reports the same group's conclusion, from work in human plasma, that CEE is mostly converted to creatinine under physiological conditions.
That chemistry is what Spillane's blood numbers look like from the outside. A molecule that survives the strong acid of an empty stomach and then turns into creatinine within minutes at the pH of the small intestine and the blood would raise serum creatinine and fail to raise serum creatine, which is what the trial recorded. Spillane's own team blamed stomach acid, citing a 2007 conference abstract that reported fast breakdown in acid; the half-lives Katseres calculated put it after the stomach rather than in it. The destination is the same either way.
Monohydrate parts company with it at exactly the point where CEE falls apart. The ISSN creatine position stand records monohydrate as fairly stable in solution at neutral pH, its conversion to creatinine in the gut as minimal regardless of transit time, and its absorption into the blood as close to complete. The long version of that chemistry, and why it also undoes the buffered-creatine pitch, is in buffered creatine vs monohydrate.
Does creatine ethyl ester raise creatinine on a blood test?
It did in the one trial that measured it. In Spillane's study, serum creatinine on CEE roughly tripled within six days, from an average of 0.95 to 2.68 mg/dL, and was still raised at days 27 and 48, while the monohydrate group stayed inside the 0.8–1.3 mg/dL normal range. Creatinine is the number a kidney panel reports, so a reading like that would be flagged. Tell whoever orders the test what you take, and which form.
Any creatine nudges that number, because creatinine is where creatine ends up; on CEE, in the one trial that measured it, the nudge was nearly a tripling. What a raised creatinine reading does and does not mean, and the sentence to say before blood is drawn, are in creatine side effects.
Should you buy creatine ethyl ester or creatine monohydrate?
Monohydrate. It carries more creatine per gram — 87.9% against 82.4% for the bare ester and about 67% for the salt — it is the form the ISSN's dosing evidence was built on, and the one trial that put CEE against it found lower serum creatine and far higher creatinine on CEE. The ISSN creatine stand, the 2011 review of novel forms and the NIH Office of Dietary Supplements reach the same verdict on the form.
The ISSN stand's wording is that claims of other forms being degraded less or taken up better than monohydrate are currently unfounded, and it names CEE among the forms that have not been shown to promote greater creatine retention. The NIH fact sheet on supplements for exercise lists CEE and buffered creatine as forms that have not shown an advantage over monohydrate. Terms used on creatine labels, including the salts and esters, are defined in the supplement label glossary.
What the research does not show
The human evidence on CEE against monohydrate is one trial, and we found no second. Spillane's had 10 men per group, all untrained and averaging about 20 years old, seven weeks of logged but unsupervised training, and supplements donated by two supplement companies; the authors declared no financial interest in the outcome. Its sections disagree about whether CEE beat placebo on muscle creatine, which is why this page leans on its blood measurements, where every section agrees on how the two creatine forms compare.
The chemistry comes from small laboratory studies in buffer solutions, not from people, and the two 2009 papers disagree about the product. Katseres's group read it as creatine and ethanol; Giese and Lecher found creatinine, and the 2011 review reports that their plasma work detected no conversion to creatine by plasma enzymes. Neither measured a real gut with food in it, and neither is a study in people. The trial's blood numbers are what tip the disagreement toward creatinine, not the test tubes on their own.
Nothing here speaks to men over 45 or to long-term use. And the comparison literature as a whole is thin: a 2026 audit in Nutrients of 343 randomised creatine trials published between 1994 and 2023 found five that compared one creatine formulation with another at all, and recorded that those few were frequently limited by unequal dosing. CEE lost on the measures it was sold on in the one trial it got. That is a strong reason to prefer monohydrate and a weak basis for any finer claim.
Where Base Work sits. Base Work is creatine monohydrate and nothing else — one ingredient, unflavoured, 300 g, 5 g a day, 60 servings. The raw material was measured by an independent laboratory (Ethos Analytics, for Vox Nutrition; raw-material lot CM20251225A; the powder made by Accobio USA Inc.) at 99.87% creatine monohydrate against a greater-than-99.5% specification. That certificate covers raw material, not a finished TARE tub; the testing page sets out what it does and does not cover. Base Work does not ship to New York addresses, for the reason given in the shipping policy.
More in this cluster: every supplement form we compare, side by side, micronized creatine vs monohydrate, the creatine research summary, how to choose a creatine supplement and creatine vs whey protein.
Sources
- Spillane M, Schoch R, Cooke M, et al. J Int Soc Sports Nutr 2009;6:6. PubMed 19228401
- Katseres NS, Reading DW, Shayya L, DiCesare JC, Purser GH. Biochem Biophys Res Commun 2009;386(2):363-367. PubMed 19524547
- Giese MW, Lecher CS. Biochem Biophys Res Commun 2009;388(2):252-255. PubMed 19660433
- Jager R, Purpura M, Shao A, Inoue T, Kreider RB. Amino Acids 2011;40(5):1369-1383. PubMed 21424716
- Kreider RB, Kalman DS, Antonio J, et al. J Int Soc Sports Nutr 2017;14:18. PubMed 28615996
- NIH Office of Dietary Supplements. Dietary Supplements for Exercise and Athletic Performance: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements
- Bucevic Popovic V, Sovulj A, Raic S, et al. Nutrients 2026;18(16):2697. PubMed 42654277