Creatine Monohydrate
Creatine
Creatine monohydrate is a nitrogenous organic acid, taken orally as an ergogenic dietary supplement to raise intramuscular phosphocreatine and improve short-duration, high-intensity performance and training adaptations. Among the most-studied supplements in humans, it has an unusually favorable safety record: multiple RCTs and meta-analyses show no serious adverse events and no measured harm to kidney or liver function in healthy people, including long-term use. The caveats worth flagging are not classic dangers: (1) it causes a small, benign rise in serum creatinine from metabolic turnover that can be mistaken for kidney injury on standard bloodwork - anyone taking it should tell their clinician and consider a cystatin C-based eGFR; (2) real-world safety data in people with pre-existing kidney disease are limited, so caution and clinician oversight are warranted there; (3) the most common real side effects are gastrointestinal upset and water-weight gain, chiefly with high loading doses. It is not a hormone and does not suppress the HPTA. It is not hepatotoxic or cardiotoxic on available human data.
Mechanism of action
Pharmacokinetics
Short for the plasma creatine molecule (roughly 1-3 hours); however, elevated muscle creatine/phosphocreatine is the pharmacodynamically relevant pool and washes out slowly - muscle stores typically return toward baseline over roughly 4-6 weeks after stopping.
Acute plasma peak within 1-2 hours; functional muscle saturation is maintained with continued daily intake and persists for weeks after discontinuation as stores gradually decline.
Oral (powder or capsule); creatine monohydrate has high oral bioavailability.
Not extensively hepatically metabolized; creatine is non-enzymatically and irreversibly converted to creatinine, which is cleared renally and excreted in urine. This metabolic turnover is why serum creatinine rises modestly during supplementation without any change in true glomerular filtration. Framing is for monitoring/washout interpretation, not test evasion.
For monitoring and washout planning, not drug-test evasion.
Physiological & performance effects
- Improves performance in short-duration, high-intensity and repeated-effort tasks and supports resistance-training adaptations (increased strength/lean mass) when combined with training
- Increases body mass, initially largely through intracellular water retention
- In postmenopausal women, creatine (studied at >=5 g/day) combined with resistance training produced small increases in lean mass and leg-press strength; effects on bone density were unclear
- May reduce cognitive performance decline under acute sleep deprivation in controlled settings
- Studied (with variable/uncertain results) as an adjunct in several clinical populations including neurodegenerative disease and aging
Adverse effects by system
No evidence of adverse cardiovascular effects in healthy humans across RCTs and safety reviews; no signal of cardiotoxicity. Water-weight gain is fluid redistribution, not a cardiac effect. No adequate data in people with significant cardiovascular disease.
No adverse hepatic effect demonstrated: meta-analytic and RCT data show no significant change in liver-function markers with supplementation.
Not a hormone and no evidence of hypothalamic-pituitary-testicular axis suppression. Testosterone was unchanged in a controlled study; however, one small RCT in male rugby players found dihydrotestosterone (DHT) rose ~56% after loading and the DHT:T ratio increased - a finding of uncertain clinical significance that has not been replicated for hard endocrine outcomes.
No human data demonstrating adverse reproductive effects. Safety data specifically in pregnancy and lactation are limited; use in these settings should be clinician-directed.
No adverse psychiatric effects established; controlled data suggest neutral-to-favorable cognitive effects (e.g., under sleep deprivation). No signal of harm.
Causes a small, transient rise in serum creatinine from metabolic turnover (not injury); meta-analysis found no significant change in glomerular filtration rate and RCTs using cystatin C found preserved kidney function in healthy people, including long-term use. Data in pre-existing kidney disease are limited - caution and clinician oversight advised.
No known adverse hematologic effects; no meaningful changes in blood counts reported in the safety literature.
No dermatologic adverse effect is established in humans. A theoretical acne/androgenic-alopecia concern is sometimes raised from the DHT-ratio finding, but no study has demonstrated that creatine causes hair loss or skin changes - this remains unproven.
HPTA suppression & recovery
Suppression: None expected - creatine is not a hormone and does not suppress the HPTA
Because there is no HPTA suppression, no post-cycle or recovery pharmacology is indicated; SERMs are not warranted for creatine and this monograph does not endorse any SERM protocol (single-agent or otherwise) for it. The only endocrine-adjacent finding is an unreplicated increase in the DHT:T ratio of uncertain significance; anyone with androgen-sensitive concerns (e.g., a history of androgenic alopecia) should discuss this with an endocrinologist rather than self-manage.
Monitoring
Cadence: Baseline before starting is reasonable, especially with any renal risk factors; periodic re-check (e.g., annually or if symptoms arise) for long-term users or those with comorbidities. Routine intensive monitoring is not required in healthy individuals.
- Flank or back pain, markedly reduced urine output, or swelling (possible renal issue - stop and seek care)
- Dark/cola-colored urine or severe muscle pain (evaluate for rhabdomyolysis from another cause)
- Persistent or severe gastrointestinal symptoms (nausea, diarrhea, cramping)
- An unexplained large rise in serum creatinine that does not fit the expected small supplementation-related increase - seek clinician evaluation with cystatin C
Contraindications
- Pre-existing kidney disease or significantly impaired renal function - safety data are limited; use only under nephrology/clinician oversight, and interpret serum creatinine cautiously
- Concurrent nephrotoxic medications (e.g., chronic NSAIDs, other nephrotoxins) - caution and clinician oversight given confounded renal monitoring
- Pregnancy and lactation - inadequate safety data; defer to a clinician
- Known intolerance; discontinue if significant gastrointestinal symptoms occur
Interaction profile
- ContraindicatedWith DNP: Additive cardiovascular strain
Check a specific combination in the interaction checker.
Reducing harm & when to stop
- Tell any clinician ordering bloodwork that you take creatine: it predictably raises serum creatinine without harming the kidneys, and a cystatin C-based eGFR avoids a false diagnosis of kidney impairment.
- If you have any kidney disease, are on nephrotoxic drugs (e.g., chronic NSAIDs), or are pregnant/breastfeeding, do not start without clinician oversight - human safety data in these groups are limited.
- Gastrointestinal upset and water-weight gain occur mainly with large single/loading doses; taking smaller amounts with food and fluids reduces GI symptoms. This is risk mitigation, not a performance-optimization recommendation.
- Use plain creatine monohydrate; avoid proprietary blends where the actual contents and contaminants are unknown.
- Stay adequately hydrated; while trials show no impairment of thermoregulation, general hydration is prudent.
- Stop and seek medical care for flank pain, sharply reduced urine output, swelling, dark urine with severe muscle pain, or an unexplained large creatinine rise that a cystatin C test cannot explain.
- This is general harm-reduction information, not medical advice; decisions about use, monitoring, and any androgen-sensitive concerns should involve a qualified clinician or endocrinologist.
Citations (11)
Every clinical claim above is tied to a primary source. Overall evidence grade A — graded to the best available evidence for its core claims.
- 01
Creatine monohydrate is a widely used ergogenic aid that raises intramuscular creatine and improves high-intensity performance and training adaptations; short- and long-term supplementation (up to 30 g/day for 5 years) is reported safe and well-tolerated in healthy people and diverse patient populations.
ReviewPMID 28615996 ↗
- 02
Mechanism: creatine is taken up into muscle and phosphorylated to phosphocreatine, buffering ATP regeneration during high-intensity effort; it is non-enzymatically converted to creatinine and renally excreted, explaining the modest rise in serum creatinine.
- 03
Meta-analysis in females found no serious adverse events, no significant difference in total or gastrointestinal adverse events, and no significant change in renal or hepatic function markers; water/weight gain was not significantly increased.
Meta-analysisPMID 32549301 ↗
- 04
Meta-analysis of kidney function found creatine causes a small, transient rise in serum creatinine (metabolic turnover) with no significant change in glomerular filtration rate, indicating preserved kidney function.
Meta-analysisPMID 41199218 ↗
- 05
Randomized double-blind trial (~10 g/day for 3 months) in healthy men using cystatin C found no renal dysfunction.
- 06
Two-year RCT of 4 g/day in older Parkinson's patients: well tolerated, main side effects gastrointestinal; serum creatinine rose from creatine degradation but cystatin C and other renal markers stayed normal.
- 07
RCT in healthy older adults undergoing resistance training showed no change in kidney function over 12 weeks of creatine supplementation.
- 08
Double-blind crossover RCT: one week of creatine (~21.6 g/day) did not compromise hydration status, thermoregulation, or increase heat-illness symptoms in dehydrated men exercising in the heat, arguing against cramping/dehydration claims.
- 09
Small crossover RCT in male rugby players: creatine loading (25 g/day x7d then 5 g/day) left testosterone unchanged but increased DHT ~56% and the DHT:T ratio ~36%; clinical significance uncertain and not replicated for hard outcomes.
- 10
Meta-analysis in postmenopausal women: creatine (>=5 g/day) with resistance training gave small gains in lean mass and leg-press strength; adverse events were mild and similar to placebo and renal indices were unchanged; bone-density effect unclear.
Meta-analysisPMID 42141930 ↗
- 11
Randomized controlled trial: a single dose of creatine monohydrate reduced sleep-deprivation-induced deterioration in cognitive performance.
Last reviewed 2026-07-06 · Verified against PubMed · Educational, not medical advice