Creatinine

What is Creatinine?

Creatinine is a waste product from the normal breakdown of creatine phosphate in skeletal muscle. It is produced at a relatively constant rate (proportional to muscle mass), filtered freely by the kidneys, and not significantly reabsorbed. This makes serum creatinine a practical marker of kidney filtration capacity (glomerular filtration rate).

What might a high or low Creatinine mean?

Rising creatinine indicates declining kidney function — the kidneys are no longer filtering waste efficiently. However, creatinine is an imperfect marker: it is influenced by muscle mass (muscular individuals have higher baseline creatinine) and does not rise until roughly 50% of kidney function is already lost. Creatinine is a PhenoAge biomarker.

What is the typical reference range for Creatinine?

The general-population reference range shown here is 62 – 106 umol/L. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.

What can affect Creatinine?

It may be higher with: Acute kidney injury, Chronic kidney disease, Dehydration, High protein diet (transient), Intense exercise (transient, from muscle breakdown), Large muscle mass, Medications (ACE inhibitors, ARBs — initial rise is expected), Creatine supplementation, NSAIDs and other nephrotoxins. It may be lower with: Low muscle mass (sarcopenia, cachexia), Pregnancy (increased kidney filtration), Liver disease (reduced creatine production), Vegetarian diet (less creatine from meat).