FitProven
Evidence Breakdown
Based on 8 studies
THE BIGGER QUESTION
Whether this one statement holds is settled above. What to actually do about it is a wider question, weighed across every claim that bears on it.
- Can you put creatine in coffee? — this claim is one of 2 weighed there
Evidence map
For & against, at a glance
Crossover Trial
Pro
Hespel P et al. · 2002Journal of Applied PhysiologyDouble-blind randomized crossover in 10 men using electrically-stimulated quadriceps contractions, and the source of the proposed mechanism. Creatine (4 × 5 g/day for 4 days) shortened muscle relaxation time by about 5%; caffeine at 5 mg/kg/day for 3 days lengthened it by about 10%; together, relaxation time showed no net change — the two act in opposite directions. Maximal torque and contraction time were unchanged throughout. The detail that matters for practice: in the same study, a *single acute* 5 mg/kg dose of caffeine had no significant effect on relaxation time. Only the chronic 3-day exposure did.
0.30
Double-blind randomized crossover in 10 men using electrically-stimulated quadriceps contractions, and the source of the proposed mechanism. Creatine (4 × 5 g/day for 4 days) shortened muscle relaxation time by about 5%; caffeine at 5 mg/kg/day for 3 days lengthened it by about 10%; together, relaxation time showed no net change — the two act in opposite directions. Maximal torque and contraction time were unchanged throughout. The detail that matters for practice: in the same study, a *single acute* 5 mg/kg dose of caffeine had no significant effect on relaxation time. Only the chronic 3-day exposure did.
Design Crossover Trial (0.75) × quality 0.40 = impact 0.30
View sourceSystematic Review
Neutral
Elosegui S et al. · 2022International Journal of Sport Nutrition and Exercise MetabolismPRISMA systematic review of 10 studies, and the best single summary of the split. On *acute* caffeine taken after creatine loading: three studies found no interference. On *chronic* caffeine co-supplementation during loading: two found interference, three found no interaction, and one found synergy. The conclusion is that creatine loading does not interfere with the acute effect of caffeine, but chronic caffeine supplementation during creatine loading could interfere with creatine's benefit. Classified neutral because it genuinely splits by protocol rather than landing on one side — which is itself the finding.
0.50
PRISMA systematic review of 10 studies, and the best single summary of the split. On *acute* caffeine taken after creatine loading: three studies found no interference. On *chronic* caffeine co-supplementation during loading: two found interference, three found no interaction, and one found synergy. The conclusion is that creatine loading does not interfere with the acute effect of caffeine, but chronic caffeine supplementation during creatine loading could interfere with creatine's benefit. Classified neutral because it genuinely splits by protocol rather than landing on one side — which is itself the finding.
Design Systematic Review (0.9) × quality 0.55 = impact 0.50
View sourceCrossover Trial
Con
Lee CL et al. · 2011European Journal of Applied PhysiologyThe cleanest test of how people actually take these. Twelve physically active men loaded creatine (0.3 g/kg/day for 5 days), then took either placebo or a single acute 6 mg/kg dose of caffeine before six 10-second cycle sprints. Creatine improved intermittent sprint performance and caffeine did not negate it — creatine plus caffeine produced significantly higher mean and peak power than control in sprints 1 and 3, and beat creatine alone in sprints 1 and 2. Double-blind and randomized. Acute caffeine on top of a creatine protocol did not blunt anything; it added.
0.45
The cleanest test of how people actually take these. Twelve physically active men loaded creatine (0.3 g/kg/day for 5 days), then took either placebo or a single acute 6 mg/kg dose of caffeine before six 10-second cycle sprints. Creatine improved intermittent sprint performance and caffeine did not negate it — creatine plus caffeine produced significantly higher mean and peak power than control in sprints 1 and 3, and beat creatine alone in sprints 1 and 2. Double-blind and randomized. Acute caffeine on top of a creatine protocol did not blunt anything; it added.
Design Crossover Trial (0.75) × quality 0.60 = impact 0.45
View sourceRCT
Con
Trexler ET et al. · 2016Journal of Strength and Conditioning ResearchThe one study that tested coffee specifically. 54 active men were randomized for 5 days to creatine 20 g/day alone, creatine plus 300 mg/day caffeine anhydrous, creatine plus instant coffee supplying 303 mg caffeine, or placebo, then tested on 1RM, reps-to-fatigue and cycle sprints. Adding caffeine in either form did not blunt creatine. A side finding worth knowing: 30.8% of the caffeine-anhydrous group reported mild GI distress, versus none in the coffee group. Read with care — creatine alone did not outperform placebo here either, so this trial had little ergogenic effect available to blunt, which makes it a weak test even though its direction is clear.
0.44
The one study that tested coffee specifically. 54 active men were randomized for 5 days to creatine 20 g/day alone, creatine plus 300 mg/day caffeine anhydrous, creatine plus instant coffee supplying 303 mg caffeine, or placebo, then tested on 1RM, reps-to-fatigue and cycle sprints. Adding caffeine in either form did not blunt creatine. A side finding worth knowing: 30.8% of the caffeine-anhydrous group reported mild GI distress, versus none in the coffee group. Read with care — creatine alone did not outperform placebo here either, so this trial had little ergogenic effect available to blunt, which makes it a weak test even though its direction is clear.
Design RCT (0.8) × quality 0.55 = impact 0.44
View sourceCrossover Trial
Pro
Hespel P et al. · 2002Journal of Applied PhysiologyDouble-blind randomized crossover in 10 men using electrically-stimulated quadriceps contractions, and the source of the proposed mechanism. Creatine (4 × 5 g/day for 4 days) shortened muscle relaxation time by about 5%; caffeine at 5 mg/kg/day for 3 days lengthened it by about 10%; together, relaxation time showed no net change — the two act in opposite directions. Maximal torque and contraction time were unchanged throughout. The detail that matters for practice: in the same study, a *single acute* 5 mg/kg dose of caffeine had no significant effect on relaxation time. Only the chronic 3-day exposure did.
0.30
Double-blind randomized crossover in 10 men using electrically-stimulated quadriceps contractions, and the source of the proposed mechanism. Creatine (4 × 5 g/day for 4 days) shortened muscle relaxation time by about 5%; caffeine at 5 mg/kg/day for 3 days lengthened it by about 10%; together, relaxation time showed no net change — the two act in opposite directions. Maximal torque and contraction time were unchanged throughout. The detail that matters for practice: in the same study, a *single acute* 5 mg/kg dose of caffeine had no significant effect on relaxation time. Only the chronic 3-day exposure did.
Design Crossover Trial (0.75) × quality 0.40 = impact 0.30
View sourceSystematic Review
Neutral
Elosegui S et al. · 2022International Journal of Sport Nutrition and Exercise MetabolismPRISMA systematic review of 10 studies, and the best single summary of the split. On *acute* caffeine taken after creatine loading: three studies found no interference. On *chronic* caffeine co-supplementation during loading: two found interference, three found no interaction, and one found synergy. The conclusion is that creatine loading does not interfere with the acute effect of caffeine, but chronic caffeine supplementation during creatine loading could interfere with creatine's benefit. Classified neutral because it genuinely splits by protocol rather than landing on one side — which is itself the finding.
0.50
PRISMA systematic review of 10 studies, and the best single summary of the split. On *acute* caffeine taken after creatine loading: three studies found no interference. On *chronic* caffeine co-supplementation during loading: two found interference, three found no interaction, and one found synergy. The conclusion is that creatine loading does not interfere with the acute effect of caffeine, but chronic caffeine supplementation during creatine loading could interfere with creatine's benefit. Classified neutral because it genuinely splits by protocol rather than landing on one side — which is itself the finding.
Design Systematic Review (0.9) × quality 0.55 = impact 0.50
View sourceCrossover Trial
Con
Lee CL et al. · 2011European Journal of Applied PhysiologyThe cleanest test of how people actually take these. Twelve physically active men loaded creatine (0.3 g/kg/day for 5 days), then took either placebo or a single acute 6 mg/kg dose of caffeine before six 10-second cycle sprints. Creatine improved intermittent sprint performance and caffeine did not negate it — creatine plus caffeine produced significantly higher mean and peak power than control in sprints 1 and 3, and beat creatine alone in sprints 1 and 2. Double-blind and randomized. Acute caffeine on top of a creatine protocol did not blunt anything; it added.
0.45
The cleanest test of how people actually take these. Twelve physically active men loaded creatine (0.3 g/kg/day for 5 days), then took either placebo or a single acute 6 mg/kg dose of caffeine before six 10-second cycle sprints. Creatine improved intermittent sprint performance and caffeine did not negate it — creatine plus caffeine produced significantly higher mean and peak power than control in sprints 1 and 3, and beat creatine alone in sprints 1 and 2. Double-blind and randomized. Acute caffeine on top of a creatine protocol did not blunt anything; it added.
Design Crossover Trial (0.75) × quality 0.60 = impact 0.45
View sourceRCT
Con
Trexler ET et al. · 2016Journal of Strength and Conditioning ResearchThe one study that tested coffee specifically. 54 active men were randomized for 5 days to creatine 20 g/day alone, creatine plus 300 mg/day caffeine anhydrous, creatine plus instant coffee supplying 303 mg caffeine, or placebo, then tested on 1RM, reps-to-fatigue and cycle sprints. Adding caffeine in either form did not blunt creatine. A side finding worth knowing: 30.8% of the caffeine-anhydrous group reported mild GI distress, versus none in the coffee group. Read with care — creatine alone did not outperform placebo here either, so this trial had little ergogenic effect available to blunt, which makes it a weak test even though its direction is clear.
0.44
The one study that tested coffee specifically. 54 active men were randomized for 5 days to creatine 20 g/day alone, creatine plus 300 mg/day caffeine anhydrous, creatine plus instant coffee supplying 303 mg caffeine, or placebo, then tested on 1RM, reps-to-fatigue and cycle sprints. Adding caffeine in either form did not blunt creatine. A side finding worth knowing: 30.8% of the caffeine-anhydrous group reported mild GI distress, versus none in the coffee group. Read with care — creatine alone did not outperform placebo here either, so this trial had little ergogenic effect available to blunt, which makes it a weak test even though its direction is clear.
Design RCT (0.8) × quality 0.55 = impact 0.44
View sourceShowing the 4 strongest of 8 studies. Tap any node to expand its detail.
Evidence
PRO (3)
PRO Crossover Trialn=100.40 Hespel P, Op't Eijnde B et al. (2002)
Creatine shortened relaxation time ~5%, caffeine lengthened it ~10%, and together there was no net change; a single acute caffeine dose had no effect
Double-blind randomized crossover in 10 men using electrically-stimulated quadriceps contractions, and the source of the proposed mechanism. Creatine (4 × 5 g/day for 4 days) shortened muscle relaxation time by about 5%; caffeine at 5 mg/kg/day for 3 days lengthened it by about 10%; together, relaxation time showed no net change — the two act in opposite directions. Maximal torque and contraction time were unchanged throughout. The detail that matters for practice: in the same study, a single acute 5 mg/kg dose of caffeine had no significant effect on relaxation time. Only the chronic 3-day exposure did.
Weighted 0.40 — Only 10 men, and the outcome is relaxation time under electrically-stimulated contractions - a mechanistic proxy rather than voluntary performance, so it is indirect for training outcomes. Maximal torque and contraction time were unchanged throughout. The funding statement could not be retrieved, so independence is unverified.
Journal of Applied Physiology
PRO Narrative Review0.40 Trexler ET, Smith-Ryan AE (2015)
Concludes caffeine may blunt creatine's ergogenic effect but that the evidence base on the interaction is limited; rules out a pharmacokinetic mechanism and proposes opposing effects on muscle relaxation time, or simple GI distress from co-ingestion
Narrative review devoted to concurrent creatine and caffeine supplementation. It concludes that caffeine may blunt creatine's ergogenic effect but that the research base on the interaction is limited — hence neutral. Its most useful contribution is ruling a mechanism out: the effect is unlikely to be pharmacokinetic, and the authors instead propose opposing effects on muscle relaxation time, or simple gastrointestinal distress from consuming both at once.
Weighted 0.40 — No sample size: narrative review. Its most defensible contribution is negative -- ruling out a pharmacokinetic mechanism -- and it is appropriately hedged about a thin primary literature rather than overclaiming, which is why it sits mid-class rather than low. But it is non-systematic, so study selection is unconstrained, and no funding or COI statement is retrievable for this article (Human Kinetics full text is paywalled), so funding is omitted.
International Journal of Sport Nutrition and Exercise Metabolism
PRO Crossover Trialn=90.35 Vandenberghe K, Gillis N et al. (1996)
Dynamic torque rose 10-23% on creatine alone and not at all with caffeine added, yet muscle phosphocreatine rose 4-6% in BOTH creatine conditions
The origin of the claim. Nine healthy men completed 6-day periods of placebo, creatine (0.5 g/kg/day, roughly 40 g/day) or creatine plus caffeine (5 mg/kg/day), with 31P-NMR of the gastrocnemius and an isokinetic knee-extension fatigue test. Dynamic torque rose 10-23% on creatine alone and not at all when caffeine was added. Critically, muscle phosphocreatine rose 4-6% in both creatine conditions — so the creatine loaded into the muscle perfectly well with caffeine on board, and whatever caffeine interfered with, it was not creatine uptake. The caffeine dose was chronic and high: for an 80 kg lifter, ~400 mg every day for six days, during a loading phase.
Weighted 0.35 — n=9, single lab, but rigorously executed and objectively measured — the 31P-NMR phosphocreatine data are what make it informative, showing creatine loaded fine with caffeine on board. Publicly funded. Held low for the tiny sample and for indirectness: 5 mg/kg/day of caffeine every day for six days during a loading phase is not how anyone actually takes caffeine.
Funding: Belgian National Medical Research Council (FGWO), grants 3.0064.94 and G.0189.96
Journal of Applied Physiology
AGAINST (4)
AGAINST Crossover Trialn=120.60 Lee CL, Lin JC et al. (2011)
Creatine plus a single acute 6 mg/kg caffeine dose produced significantly higher mean and peak power than control in sprints 1 and 3, and beat creatine alone in sprints 1 and 2 -- acute caffeine did not blunt the creatine benefit, it added to it
The cleanest test of how people actually take these. Twelve physically active men loaded creatine (0.3 g/kg/day for 5 days), then took either placebo or a single acute 6 mg/kg dose of caffeine before six 10-second cycle sprints. Creatine improved intermittent sprint performance and caffeine did not negate it — creatine plus caffeine produced significantly higher mean and peak power than control in sprints 1 and 3, and beat creatine alone in sprints 1 and 2. Double-blind and randomized. Acute caffeine on top of a creatine protocol did not blunt anything; it added.
Weighted 0.60 — n=12 physically active men in a double-blind randomised crossover, publicly funded with no declared conflicts -- a clean design for its class. Small, and strictly acute: it tests one 6 mg/kg caffeine dose on top of a completed 5-day creatine load, so it speaks to acute co-ingestion and not to habitual daily caffeine intake alongside chronic creatine use, which is the scenario people usually ask about.
Funding: National Science Council, Taiwan (NSC 97-2410-H-034-028)
European Journal of Applied Physiology
AGAINST RCTn=540.55 Trexler ET, Smith-Ryan AE et al. (2016)
Adding caffeine (anhydrous or as coffee) to creatine did not blunt 1RM, reps-to-fatigue or cycle-sprint gains; GI distress in 30.8% of the caffeine-anhydrous group vs 0% with coffee
The one study that tested coffee specifically. 54 active men were randomized for 5 days to creatine 20 g/day alone, creatine plus 300 mg/day caffeine anhydrous, creatine plus instant coffee supplying 303 mg caffeine, or placebo, then tested on 1RM, reps-to-fatigue and cycle sprints. Adding caffeine in either form did not blunt creatine. A side finding worth knowing: 30.8% of the caffeine-anhydrous group reported mild GI distress, versus none in the coffee group. Read with care — creatine alone did not outperform placebo here either, so this trial had little ergogenic effect available to blunt, which makes it a weak test even though its direction is clear.
Weighted 0.55 — n=54 analysed across four arms (13-14 per group), only 5 days. Independently funded with no supplement-industry money, but a weak test of the claim: creatine alone did not outperform placebo either, so the trial had little ergogenic effect available to blunt. No COI statement (journal norm of the era).
Funding: National Strength and Conditioning Association Foundation; NIH/NCATS grant 1KL2TR001109
Journal of Strength and Conditioning Research
AGAINST Narrative Review0.35 Antonio J, Brown AF et al. (2025)
Concludes that short-term creatine intake together with caffeine below 5 mg/kg/day likely does not produce opposing muscle effects, while acknowledging the proposed antagonism at the sarcoplasmic reticulum
ISSN expert consensus paper that addresses the interaction directly, concluding that short-term creatine and caffeine intake below 5 mg/kg/day likely does not cause opposing muscle effects. It acknowledges the proposed antagonism — opposing effects on calcium kinetics at the sarcoplasmic reticulum, delaying muscle relaxation — while noting caffeine could even aid creatine transport by activating the sodium-potassium ATPase pump. Weighted as a narrative review, not primary evidence. Note that the widely-repeated claim that the ISSN's 2017 creatine position stand settles this question is false: that paper does not mention caffeine at all.
Weighted 0.35 — Expert consensus with no primary data and no pooled sample, so sample_size is omitted. The paper reports no funding, but the disclosure list is heavy with creatine-industry ties (ISSN leadership, Alzchem and Create scientific advisory boards, industry-sponsored creatine research). It is directly on point for the claim, which is why it sits at the top of the narrative-review band rather than lower.
Funding: none declared
Journal of the International Society of Sports Nutrition
AGAINST Crossover Trialn=70.30 Vanakoski J, Kosunen V et al. (1998)
Caffeine pharmacokinetics unaffected by creatine and creatine absorbed normally alongside caffeine; no performance benefit from creatine alone or combined
Randomized, double-blind, placebo-controlled crossover in 7 trained athletes comparing placebo, acute caffeine (7 mg/kg), creatine (3 × 100 mg/kg/day for 3 days) and both, across maximal cycle bouts and 45 minutes of aerobic cycling. Its value here is pharmacokinetic rather than performance-based: caffeine's pharmacokinetics were unaffected by creatine, and creatine was absorbed normally alongside caffeine. That rules out an absorption-level interaction. Weak as a performance test — with only 7 subjects, creatine alone produced no benefit either, so there was nothing available to blunt. No DOI is indexed for this paper; the PubMed record is the source.
Weighted 0.30 — n=7 across four conditions — far below the point where a performance null carries information, and creatine alone produced no benefit either, so there was nothing available to blunt. Sound as a pharmacokinetic result (its real contribution: no absorption-level interaction), very weak as a performance test. No funding or COI statement (1998 journal norm), so independence is unverified.
International Journal of Clinical Pharmacology and Therapeutics
NEUTRAL (1)
NEUTRAL Systematic Review0.55 Elosegui S, López-Seoane J et al. (2022)
Acute caffeine after creatine loading showed no interference in 3 studies; chronic co-supplementation gave 2 interference, 3 null, 1 synergy
PRISMA systematic review of 10 studies, and the best single summary of the split. On acute caffeine taken after creatine loading: three studies found no interference. On chronic caffeine co-supplementation during loading: two found interference, three found no interaction, and one found synergy. The conclusion is that creatine loading does not interfere with the acute effect of caffeine, but chronic caffeine supplementation during creatine loading could interfere with creatine's benefit. Classified neutral because it genuinely splits by protocol rather than landing on one side — which is itself the finding.
Weighted 0.55 — k=10 studies, no pooled sample size reported and no meta-analysis - a vote count across small, heterogeneous trials rather than a quantitative synthesis. The funding statement is behind a paywall, so independence could not be verified.
International Journal of Sport Nutrition and Exercise Metabolism