Does creatine affect your sleep?
Creatine may improve how your sleep feels, but the evidence comes exclusively from small studies and objective sleep measurements show no effect. Do not take creatine primarily for better sleep, but if you are already using it for sport, there is no indication that it worsens sleep.
Creatine appears to improve how people experience their sleep. In a small randomised study with 14 men (crossover design), participants who took 20 grams of creatine per day for one week scored significantly better on a subjective sleep quality scale compared with placebo. The effect was medium-sized (d = 0.81) and participants also went to bed earlier. This is a preliminary finding from a single small study, but the difference was statistically clear.
What people feel themselves and what a measuring device records diverged in that same study, however. Objective sleep measurements via actigraphy (a wristwatch that records movement) showed no difference whatsoever in sleep onset latency, sleep efficiency or total sleep time. Creatine may therefore improve how your sleep feels without changing the measurable sleep structure. This difference between subjective and objective is important to understand.
A second small RCT, involving 21 women who took 5 grams of creatine per day for six weeks in combination with strength training, found a different pattern. On training days, women in the creatine group slept significantly longer than women in the placebo group. On rest days and on the general sleep quality scale (PSQI) there was no difference. This suggests that creatine may specifically extend the recovery period after physical exertion slightly, but this is not a broad effect on sleep in general.
A narrative review (an overview article that describes the literature but does not perform a meta-analysis) concludes that creatine may also partially offset cognitive decline caused by sleep deprivation. Mechanistically, this is explained by the fact that creatine and phosphocreatine serve as a rapid energy reserve in the brain, which is relevant when brain activity comes under extra pressure due to sleep deprivation. There is also limited evidence that cognitive processing after experimental sleep deprivation or during ageing improves with creatine supplementation. The researchers of the review emphasise themselves, however, that the findings are preliminary and inconsistent.
As an additional effect, creatine also reduced muscle soreness after exercise in the small RCT (d = -0.59). This is relevant because muscle soreness can indirectly affect sleep, but this relationship has not been directly investigated in the available studies.
All findings are based on two small RCTs (n=14 and n=21) and one narrative review. None of the studies is large enough to draw definitive conclusions. The objective sleep measurements did not align with the subjective improvements, which complicates interpretation.