Creatine: What It Actually Does and What It Does Not

Creatine is the best-studied supplement in strength training and also the one whose effect is most often oversold. A meta-analysis found small but significant effect sizes, including 0.17 for body composition, with a larger effect for upper-body exercise (0.42) than lower-body (0.21) or total-body work (0.13) [1].

A separate meta-analysis of 53 studies on upper-limb strength reported a global effect size of 0.317, concentrated in efforts under three minutes and largely independent of dose or protocol [2]. Two independent data sets, the same picture: a real, moderate benefit.

The mechanism explains this distribution well. Creatine raises muscle phosphocreatine stores, meaning a greater capacity to rebuild ATP quickly between reps and sets. The largest benefit therefore lands on short, repeated efforts — which dominate upper-body work.

The same mechanism explains why the effect is hard to see in a single heavy attempt. One maximal rep does not deplete the phosphagen system enough for its larger capacity to matter.

In the same analysis, the body-composition effect was larger after a loading protocol (0.26) than on a maintenance dose (0.04) [1] — but that comparison mostly measures how fast the muscle saturates, not the long-run outcome. Loading shortens the time to full effect; it does not raise the ceiling.

Practically that means 3–5 g a day with no loading phase reaches the same place in a few weeks. Loading is worth it only when you need the effect by a specific date.

It is also worth remembering what these numbers do not say. An effect size of 0.3 is a few percent on the bar, not the difference between a stall and progress — your training dose still comes from volume and recovery.

It is worth settling the practical questions that generate the most confusion. Timing does not matter, because the effect depends on muscle saturation rather than blood concentration at any moment. Supplementing on rest days makes sense for the same reason.

Hydration deserves attention, though not for the usual reason. Creatine increases intracellular water content, so fluid needs rise slightly — an argument for drinking normally rather than for any special protocol.

Creatine usually does not change your e1RM on a single heavy set — it changes how many reps you hold on the second and third set. If you are looking for the effect, watch rep drop-off across sets at the same load rather than your best single.

The second visible effect is a faster gain in body weight over the first two weeks, driven mainly by water retention inside the muscle. Worth knowing so you do not read it as new tissue, or as a failing fat-loss phase.

The last thing worth settling is the order of priorities. An effect size around 0.3 is real, but smaller than the difference between a plan with 10 and 16 weekly sets per muscle, or between six and eight hours of sleep.

Creatine is a good addition to a working system rather than a way around its gaps. Supplementing while missing three sessions a month changes less than recovering those three sessions would.