How Does Creatine Work? ATP and Creatine Explained

ATP (adenosine triphosphate) is the energy currency of every cell. Your muscles, your brain and your heart all run on it. Creatine matters because it helps your cells rebuild ATP quickly when demand spikes: during a hard set, a sprint or a mentally demanding day. Here is how the system works, in plain language. For the bigger picture, see our complete guide to creatine for women.

ATP: your cells' instant energy

When a cell needs energy, it splits ATP into ADP (adenosine diphosphate) and a free phosphate. That split releases the energy that powers a muscle contraction or a nerve signal (Kreider et al., 2017).

The catch: cells keep only a small amount of ATP on hand. During an all-out effort it would run low within seconds if nothing refilled it. Your body has slower backup systems that break down carbohydrate and fat, but they cannot keep up with a sudden burst of demand.

Creatine's role: the fast refill

About 95% of your body's creatine sits in skeletal muscle, with small amounts in the brain. Roughly two thirds of the creatine in muscle is stored as phosphocreatine (PCr) (Kreider et al., 2017).

When ATP is used up, phosphocreatine hands its phosphate back to ADP, turning it into ATP again. An enzyme called creatine kinase runs this reaction:

Phosphocreatine + ADP → ATP + Creatine

This is the fastest way your body can rebuild ATP, which is why it matters most in short, intense efforts such as a heavy set, a hill sprint or an interval. The same creatine kinase system also shuttles energy inside cells, from the places where ATP is made to the places where it is used.

Where your creatine comes from

Your body breaks down about 1 to 2% of its muscle creatine every day and has to replace roughly 1 to 3g a day, depending on muscle mass. About half comes from food such as red meat and fish. The rest is made in the liver and kidneys from the amino acids arginine and glycine (Kreider et al., 2017).

On a normal diet, muscle creatine stores are only about 60 to 80% full. Women tend to have lower creatine stores than men and eat less creatine through food (Smith-Ryan et al., 2021), and people who eat little or no meat or fish start lower still. More on that in creatine for vegetarians and vegans.

What supplementing does

Taking creatine every day raises muscle creatine and phosphocreatine by about 20 to 40% (Kreider et al., 2017). With fuller stores, your muscles can keep rebuilding ATP a little longer during hard efforts. Over weeks of training, that shows up as more reps and more strength: in a review of 22 studies, creatine plus resistance training increased maximal strength by about 8% more than training alone (Rawson and Volek, 2003).

You do not need a loading phase. A daily 3g dose raised muscle creatine by about 20% over 28 days, the same increase as six days of 20g a day (Hultman et al., 1996). Our dosage guide explains how much creatine women should take.

Creatine and your brain

Your brain uses a lot of ATP and keeps its own small creatine store. A systematic review of randomized trials found that creatine may improve short-term memory and reasoning in healthy people, with possible benefits for older and stressed people (Avgerinos et al., 2018). Read more on creatine for brain fog and focus.

The cycle in short

1. You need energy fast, so ATP is split into ADP.
2. Phosphocreatine rebuilds ATP from ADP within moments.
3. When you rest, your cells use ATP from slower systems to turn creatine back into phosphocreatine, ready for the next effort.

How to take creatine

Consistency fills your stores, not timing (see when to take creatine). Each mujo gummy contains 1.25g creatine monohydrate. Start with 3 gummies a day (3.75g), which makes one 90-gummy jar last a month. For the full 5g used in most studies, take 4 gummies a day. Try Watermelon or Pineapple Creatine Gummies, and see our Eurofins lab results.

This article is for information only and is not medical advice. If you are pregnant, breastfeeding or have kidney disease, talk to your doctor before taking creatine.