What creatine actually does, by mechanism

1. 01

   Recycles ATP through the phosphocreatine system

   Muscle runs on ATP, but only stores ~2-3 seconds' worth at full intensity. Phosphocreatine is the rapid refill: it donates its phosphate to turn spent ADP back into ATP within milliseconds. Supplementing raises muscle phosphocreatine stores by ~20% (Harris et al. 1992), extending how long you can hold maximal output before the slower glycolytic system takes over. This is the entire mechanism; everything else is downstream of buffering ATP for short, hard efforts under ~10 seconds.

2. 02

   Adds reps, which adds training volume

   The practical effect of more available ATP is 1-2 extra reps per set at a given load, or holding a heavier load for the same reps. Over weeks, that extra volume is what drives the strength gain; creatine does not build muscle directly, it lets you do more of the work that builds muscle. Rawson & Volek 2003 reviewed 22 studies and found creatine plus resistance training produced ~8% greater strength and ~14% greater rep performance than training plus placebo.

3. 03

   Raises lean body mass ~1-2 kg

   The scale typically moves up 1-2 kg in the first 2-4 weeks. The first portion is intracellular water drawn into muscle cells (cell volumization), not fat or subcutaneous bloat (Francaux & Poortmans 2003). The rest accrues over months as real contractile tissue from the added training volume. Body composition improves: the gain is muscle and muscle-bound water, not fat.

4. 04

   Improves high-intensity and repeated-sprint performance

   Beyond the weight room, creatine improves repeated-sprint work and any sport with short maximal bursts and incomplete recovery: sprints, intervals, combat sports, team-sport repeated efforts. A meta-analysis (Lanhers et al. 2017) confirmed significant gains in upper- and lower-body maximal strength. The effect is largest for efforts under ~30 seconds with short rest; it does little for steady-state aerobic endurance.

5. 05

   Supports cognition under stress (emerging)

   The brain also uses phosphocreatine for energy, and creatine crosses into it slowly. The clearest signal is under metabolic stress: Avgerinos et al. 2018 (systematic review) found improvements in short-term memory and reasoning, strongest in older adults and during sleep deprivation. In well-rested young adults the cognitive effect is smaller and less consistent. This is a real but secondary use case, not the main reason most people take it.

6. 06

   May support bone and muscle in aging (with training)

   In older adults, creatine plus resistance training preserves lean mass and may slow bone loss better than training alone. Chilibeck et al. 2015 (1-year RCT in postmenopausal women) found creatine plus training improved hip bone geometry versus placebo plus training. The benefit is consistently contingent on the training stimulus; creatine without resistance exercise does not produce these effects.

7. 07

   How fast it works, and the dose that does it

   Two routes to the same saturated muscle store (Hultman et al. 1996). Maintenance: 3-5 g/day reaches full saturation in ~3-4 weeks, the simplest protocol. Loading: 20 g/day split into 4 doses for 5-7 days saturates in ~1 week, then drop to 3-5 g/day, at the cost of more GI upset and a faster water-weight jump. Final muscle creatine is identical either way. No cycling is needed, and timing relative to workouts barely matters; consistency is what saturates the store. Monohydrate is the only form with the evidence behind it; the 'advanced' forms (HCl, buffered, ethyl ester) cost more without outperforming it.

What people ask us next.

Q01

What does creatine actually do in the body?

It refills your fast energy system. Creatine is stored in muscle as phosphocreatine, which regenerates ATP, the cell's energy currency, during short maximal efforts under ~10 seconds. Supplementing raises muscle phosphocreatine ~20% (Harris 1992), so you can do 1-2 more hard reps or sprints before fatiguing. Over a training block that extra volume drives ~5-15% greater strength and ~1-2 kg more lean mass (Kreider 2017).

Q02

How long does creatine take to work?

Muscle stores saturate in ~3-4 weeks at 3-5 g/day, or ~1 week if you load with 20 g/day for 5-7 days first (Hultman 1996). The performance benefit appears once stores are saturated, not on day one; creatine is not a pre-workout stimulant and you feel nothing acutely. Final saturation is identical whether you load or not, so loading only buys speed.

Q03

Does creatine build muscle directly?

No, indirectly. Creatine does not signal muscle growth itself; it lets you perform more total training volume (extra reps and sprints), and that added volume is what builds muscle over weeks. Rawson & Volek 2003 found creatine plus lifting produced ~8% more strength than lifting plus placebo. Part of the early 1-2 kg gain is also intracellular water (Francaux 2003), which is muscle-bound, not fat.

Q04

Does creatine help the brain?

There is emerging evidence, strongest under stress. The brain uses phosphocreatine for energy, and Avgerinos et al. 2018 found creatine improved short-term memory and reasoning, with the largest effects in older adults and during sleep deprivation. In well-rested young people the cognitive effect is smaller and less consistent. It is a legitimate secondary benefit, not the primary reason most people supplement.

Q05

What is the right dose of creatine?

3-5 g/day of creatine monohydrate, taken every day. Scale to ~0.03 g/kg for body size. Loading (20 g/day for 5-7 days) only speeds up saturation by a couple of weeks and is optional; it also causes more GI upset. No cycling is needed, timing around workouts barely matters, and plain monohydrate beats the pricier HCl or buffered forms on cost with no loss of effect.

Q06

Does everyone respond to creatine?

Most people do, but roughly 20-30% are 'non-responders' whose muscle creatine is already near-saturated from diet, typically high meat-eaters (Syrotuik & Bell 2004). Vegetarians and vegans tend to respond most strongly because their baseline stores are lower. If you see no strength change after 4-6 weeks of consistent 5 g/day with progressive training, you may be a non-responder; the supplement is still safe, it just has less room to help you.