Creatinine explained

A waste product made at a steady rate by muscle and removed almost entirely by the kidneys. Because production is steady, the blood level reflects how well it is being cleared. Muscle mass affects it, so the same number does not mean the same thing in everyone — the KDIGO guideline sets out how creatinine is used to estimate filtration and where that estimate is unreliable. It becomes the eGFR: The conversion already accounts for age and sex, which is why the raw creatinine and the eGFR can tell different stories about the same person.

Fasting: Not needed for creatinine itself. Best time: Any time, usually with the rest of the panel. Avoid beforehand: A large meat meal for 24 hours; Creatine supplements for 24 hours; Heavy exercise for 2 days. Be normally hydrated — dehydration is the commonest reason for a mildly raised result.

Commonly: dehydration; muscle mass, and heavy exercise in the days before; a high-protein or large meat meal; creatine supplements; anti-inflammatory painkillers and some antibiotics. A single result is not a diagnosis. Values are read against the laboratory's own reference range and alongside your history, your symptoms and the rest of the panel — which is why every package includes a doctor to go through them with you.

At Smart Care Polyclinic, 29 Doha Centre, Al Maktoum Rd, Deira, Dubai. Walk in during opening hours or call +971 (0)4 379 3562.