Creatine and caffeine

Vandenberghe and colleagues followed 9 healthy men during 6 days of creatine loading (0.5 g per kg per day), either alone or combined with 5 mg of caffeine per kg per day. Both protocols increased muscle phosphocreatine by 4 to 6%. But in an intermittent exercise test, torque increased by 10 to 23% with creatine alone, and not at all with the combination. The authors concluded that caffeine completely eliminated creatine's effect on performance.

Hespel and colleagues, from the same Leuven team, tested 10 volunteers in a double-blind crossover trial. Creatine (4 doses of 5 g per day for 4 days) shortened muscle relaxation time by about 5%. Caffeine taken for 3 days (5 mg per kg per day) lengthened it by about 10%. Combined, the two no longer produced any change: caffeine's effect prevailed. This suggests a possible mechanism, not proof of reduced performance in real-world conditions.

The review by Trexler and Smith-Ryan summarizes the evidence: creatine consistently improves short, intense efforts, caffeine has more variable effects on strength and sprinting, and studies testing the two together are rare. The authors consider a pharmacokinetic interaction unlikely. They propose two possible explanations: opposing effects on muscle relaxation, and digestive discomfort when both are taken at the same time.

In 2024, Mabrey and colleagues gave 12 trained athletes creatine nitrate (5 g per day), caffeine (400 mg per day) or both for 7 days. None of the protocols improved measured performance in resistance training or the Wingate test. The combination slightly improved performance on a cognitive test (Stroop), with no adverse effects reported.

Creatine's effect comes from muscle saturation over several weeks, not from that day's dose: keep taking it daily. The negative findings concern repeated high doses of caffeine (5 mg per kg, or around 350 mg for 70 kg) during a loading phase. Moderate coffee consumption has not been tested. As a precaution, although this has not been demonstrated, avoid taking creatine at the same time as a high dose of caffeine, especially during a loading phase.

For your dose, use the creatine calculator and the caffeine calculator. For timing around workouts, see creatine before or after exercise .

The two negative trials involved 9 and 10 men, both from the same laboratory, with high, repeated doses of caffeine over several days. They have not been replicated on a large scale. The 2024 trial used creatine nitrate, not monohydrate, over 7 days in 12 athletes: it can neither confirm nor rule out the effect. We therefore do not know whether your daily coffee reduces the benefit of your creatine. That is why the checker classifies this pair as requiring caution, rather than as a documented interaction.