Creatine is a compound your body makes itself, mainly in the liver and kidneys, from three amino acids: arginine, glycine and methionine.

Around 95% of it is stored in skeletal muscle. Smaller amounts are found in the brain, heart and other tissues with high energy demands.

Inside cells, creatine is converted into phosphocreatine, which acts as a rapid reserve for regenerating ATP, the molecule cells use as immediate energy. That system matters most during short, intense efforts lasting seconds rather than minutes.

You also get creatine from food, almost entirely from meat and fish. People who eat little or no animal produce therefore tend to have lower stored creatine, which is one reason creatine has become popular with vegetarians and vegans.

Creatine is one of the most heavily researched supplements in existence. That does not mean every claim made about it is proven. It helps to separate the evidence into three tiers.

Yes, but probably not in the way supplement marketing suggests.

Creatine monohydrate is the form used in almost all of the research above. Alternatives such as creatine hydrochloride, creatine ethyl ester, buffered creatine and liquid creatine are often sold at a premium with claims of better absorption or fewer side effects. None has been convincingly shown to outperform monohydrate, and some, such as creatine ethyl ester, have performed worse in studies.

"Micronised" or "ultra-fine" creatine is still creatine monohydrate. The particles are simply smaller, which helps the powder disperse in liquid and reduces grittiness. That is a practical benefit rather than a biological one, but it is not trivial: creatine only works if you take it consistently, and a powder that is unpleasant to drink tends to get abandoned.

Almost all creatine on the global market is produced by a small number of chemical manufacturers. According to Alzchem, its plant in Trostberg, Germany is the only creatine monohydrate producer in the Western Hemisphere, with the remainder of dietary supplement creatine made in China.

Read Alzchem's supplier profile

Alzchem sells its creatine under two brand names:

• Creapure®, aimed at sports nutrition
• Creavitalis®, aimed at general health and nutrition

Both are pure creatine monohydrate made at the same German facility. The difference is positioning rather than chemistry.

This does not mean creatine made elsewhere is unsafe. Many products using unbranded creatine are perfectly good, particularly when the finished product is independently tested. It does mean that a named, traceable raw material gives you one more layer of assurance about what you are actually taking.

Gummies are the fastest-growing creatine format, and the most problematic.

Creatine is unstable in warm, moist, acidic conditions, which is exactly what gummy manufacturing involves. In US testing commissioned by supplement maker NOW, five of twelve creatine gummy brands were found to contain little or no creatine. Other independent tests have reported similar results.

Read the report on creatine gummy testing

Some gummies do contain what they claim. But because the format is harder to manufacture and harder to test, we have not included any gummy products in this ranking. If you prefer gummies, ask the brand for a recent, independent, finished-product certificate of analysis.

We focused on people taking creatine as a daily, long-term habit. We scored each product on:

• Form: creatine monohydrate only
• Raw material transparency: whether the creatine source is named and traceable
• Formulation: whether the product is creatine alone or includes sweeteners, flavourings and other additives
• Dose: whether a single serving provides at least the 3g used in the authorised claims
• Testing: what the brand states about independent testing of the finished product
• Manufacturing: where the finished product is made and to what standards
• Ease of daily use: mixability, taste and format
• Price: considered, but not the deciding factor

We did not rank products on claimed effects, because every product in this list contains the same active molecule.

The authorised UK health claims are based on 3g of creatine per day. Most products, including our top pick, provide 5g per serving, which is the amount most commonly used in research and recommended by the International Society of Sports Nutrition.

A "loading phase" of around 20g per day for five to seven days saturates muscle stores faster, but it is not necessary. Taking a standard daily dose reaches the same level within about three to four weeks, with less chance of stomach discomfort.

Timing matters far less than consistency. Take it at whatever time of day you are most likely to remember.

Read the International Society of Sports Nutrition position stand on creatine

For healthy adults, creatine monohydrate has one of the best safety records of any supplement, with research spanning several decades.

A few points are worth knowing:

• Water retention: creatine draws water into muscle cells, so a small increase in body weight in the first few weeks is normal.
• Kidney blood tests: creatine can raise blood creatinine, a marker doctors use to estimate kidney function, without indicating kidney damage. If you have a blood test, tell your doctor you take creatine.
• Existing kidney disease: anyone with kidney disease, or taking medication that affects the kidneys, should speak to a doctor before using creatine.
• Pregnancy and breastfeeding: there is not enough research to recommend creatine supplementation, so seek medical advice first.
• Hair loss: this concern stems largely from a single small 2009 study that measured a hormone, not hair loss itself. It has not been replicated.

Read a scientific review of common creatine misconceptions

Adults over 55 who do resistance training. This is the group covered by a specific authorised health claim, and maintaining strength is one of the most practical priorities in healthy ageing.

Vegetarians and vegans. With little or no dietary creatine, baseline stores tend to be lower.

People who do high-intensity or interval training. This is where the evidence on performance is strongest.

If you are none of these, creatine is unlikely to do you harm, but the case for it is less clear-cut.