What is creatine?
The most common form of creatine is creatine monohydrate. It’s made from amino acids that are naturally produced by the body and obtained from dietary sources such as meat and fish.
How does creatine work?
Before we get into what creatine does, it helps to understand its role in muscle contraction.
Within our bodies—and more specifically in our muscles—creatine binds with phosphate to form a usable, high‑energy compound called phosphocreatine (PCr). Muscle contraction is powered by breaking down ATP (adenosine triphosphate), which is the only direct energy source your muscles can use for contractile activity.
Stored ATP is depleted within seconds, after which phosphocreatine rapidly regenerates ATP to sustain maximal effort for roughly 10 seconds. ADP (adenosine diphosphate) is converted back into ATP. This regeneration occurs in a fraction of a second and is driven by three main energy pathways. One of these pathways uses creatine phosphate as the energy source to convert ADP back into ATP.
Creatine, in the form of creatine phosphate, simply acts as a high‑energy reserve that helps regenerate ADP back to ATP. This happens while slower metabolic pathways (the other two energy systems that also regenerate ATP) are ramping up to meet the increased demand. Our muscles actually store more creatine phosphate than ATP. Together, stored ATP and the near‑instant regeneration of ATP via creatine phosphate support maximal power output during short, high-intensity efforts (roughly 5–15 seconds), such as heavy resistance training.
What does creatine do?
We now know what creatine is and how our bodies use it, so let’s look at how it can help your workouts and support muscle hypertrophy (increased muscle size).
The theory behind using creatine for muscle hypertrophy is that supplementing with it can increase creatine phosphate stores in the muscles. This, in turn, can slightly increase the maximum power your muscles can produce at any one time and may allow small increases in reps or training load over time. This additional training volume increases mechanical tension and overall workload, which are key drivers of muscle growth.
Summary
Creatine does not directly cause muscle growth, but it enhances the body’s ability to perform high-intensity work. By improving ATP regeneration, it can support small increases in strength, power, and training volume over time. These improvements contribute to the key drivers of hypertrophy, such as mechanical tension and total workload.
Creatine also:
- supports recovery between sets
- may improve strength and power output
- has emerging evidence for cognitive and neurological benefits
Side Effects
As with any supplement or performance‑enhancing product, side effects are sometimes reported, and creatine is no exception. Some of the most commonly reported side effects of creatine use are listed below:
Evidence-based side effects:
- Increased body mass (mainly water retention in muscle)
- Possible mild gastrointestinal discomfort (especially with high doses
Not well supported by evidence:
- Cramping, dehydration, or injury risk (often reported anecdotally but not consistently observed in studies)
In addition to these side effects, it’s possible there are others. Supplements affect people differently, and many people who use creatine do not report any side effects at all.