What is Creatinine?
Creatinine is a waste product from normal muscle metabolism that the kidneys filter out of the blood. Because production is fairly steady, the blood level reflects how well the kidneys are filtering. Creatinine is used to calculate the estimated glomerular filtration rate (eGFR), the standard measure of kidney function.
Why it matters
Rising creatinine (and falling eGFR) signals declining kidney function, which is often silent until advanced. It also guides safe dosing of medications cleared by the kidneys.
What it measures
The blood concentration of creatinine, used with age, sex, and body size to estimate eGFR.
Reference & optimal ranges
Reference ranges vary by lab, assay, age, and sex. The ranges below reflect commonly published adult intervals and are for education only always interpret results with the range printed on your own lab report and a clinician.
High creatinine suggests reduced kidney filtration, though muscular individuals and dehydration can also raise it.
Common symptoms
- Often none early
- Fatigue, swelling, or changes in urination if kidney disease is advanced
Potential causes
- Chronic or acute kidney disease
- Dehydration
- High muscle mass or heavy meat intake
- Certain medications (NSAIDs, some antibiotics)
- Urinary obstruction
Low creatinine usually reflects low muscle mass and is rarely a concern.
Common symptoms
- None typically
Potential causes
- Low muscle mass
- Aging
- Pregnancy
- Some liver conditions
How to improve your Creatinine
Lifestyle
Stay hydrated
Dehydration transiently raises creatinine; adequate fluids support kidney function.
Nutrition
Moderate protein, manage blood pressure and sugar
Controlling blood pressure and diabetes is the most important way to protect kidney function.
Exercise
Note timing
Very intense exercise and high muscle mass raise creatinine independent of kidney health.
Sleep
General health
Supports cardiovascular and metabolic health that protects the kidneys.
Frequently asked questions
Scientific references
- Creatinine Test MedlinePlus, U.S. National Library of Medicine
- Creatinine and eGFR Testing.com
Educational information, not medical advice. This page is for general education and does not replace diagnosis or treatment by a licensed clinician. Do not start, stop, or change any medication, supplement, or treatment based on this content. Reference and optimal ranges vary between laboratories interpret your results with the range on your own report and a qualified professional.