Creatine monohydrate

What it is

Creatine monohydrate loads the muscle's phosphocreatine pool, the store that rapidly regenerates ATP during short bursts of intense effort. It is one of the better-studied over-the-counter supplements and is taken for energy and physical performance, and in this data also under joint support.

Used for

• Energy
• Joints

What to know while taking it

Timing and food are flexible, as it can be taken with or without a meal. It draws water into muscle, so adequate fluid intake matters throughout the day. It also raises measured serum creatinine simply because creatine breaks down into it, without any injury to the kidneys, which in turn lowers a calculated eGFR; anyone having kidney markers checked should mention that they take it, so a harmless laboratory shift is not read as kidney disease.

When to see a doctor

A rising creatinine accompanied by real symptoms, such as reduced urine output, swelling, or persistent nausea, is not the expected laboratory artefact and warrants seeing a doctor. Pre-existing kidney disease is a reason to ask a doctor before starting.

Worth knowing

• Drink enough water
• Raises measured creatinine without harming kidneys

Markers to watch

• Creatinine
• eGFR