Creatinine is a waste product produced by the normal breakdown of creatine — a compound used by muscles to generate energy. It's filtered from the blood by the kidneys and excreted in urine. Because the kidneys handle creatinine predictably, its blood level is a reliable measure of how well they're working.
Normal range and eGFR
Normal creatinine values differ by sex and muscle mass — roughly 60–110 µmol/L for women and 70–120 µmol/L for men, though ranges vary by lab. More useful than the raw creatinine is the estimated glomerular filtration rate (eGFR), which is calculated from creatinine along with age and sex. eGFR above 60 mL/min/1.73m² is generally normal; values below this indicate reduced kidney function.
eGFR is categorised into stages of chronic kidney disease (CKD): G1 (≥90), G2 (60–89), G3a (45–59), G3b (30–44), G4 (15–29) and G5 (below 15). Lower stages indicate more severe impairment.
Causes of elevated creatinine
- Dehydration — reduces kidney blood flow and raises creatinine transiently; resolves with fluids
- High-protein diet — large amounts of dietary meat increase creatinine production
- Intense exercise — muscle breakdown produces extra creatinine
- Acute kidney injury — rapid rise often due to dehydration, medications or infection
- Chronic kidney disease — gradual rise over months or years
- Medications — NSAIDs, ACE inhibitors and nephrotoxic antibiotics can affect creatinine
The importance of tracking trends
A single creatinine level is a snapshot. The trend — whether it's stable, slowly rising or rapidly deteriorating — matters far more for clinical decisions. Looms allows you to log and chart creatinine results over time, making it easy to bring a visual trend to your next nephrology or GP appointment.