Lab test glossary · Kidney
Creatinine: what it means
Also known as: serum creatinine
Creatinine is a muscle waste product cleared by the kidneys; it's a core measure of kidney function and feeds the eGFR calculation.
What it measures
Creatinine is a waste product of normal muscle metabolism that your kidneys filter out of the blood. When kidney filtering slows, creatinine builds up — so a higher level generally means reduced kidney clearance. Because it's tied to muscle mass, muscular people can run higher naturally.
Typical range
Often roughly 0.7–1.3 mg/dL for men and 0.6–1.1 mg/dL for women, influenced by muscle mass, age, and hydration.
Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.
What a high result can mean
- Reduced kidney function
- Dehydration
- High muscle mass or a very high-protein/creatine intake
- Some medications
A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.
What a low result can mean
- Low muscle mass
- Pregnancy
Why the trend matters
A single creatinine has to be read against your own baseline; the trend over time is what reveals a gradual decline in kidney function that any one value might miss.
When to talk to your doctor
A creatinine rising over successive tests, or a low eGFR, is worth discussing with your doctor.
Frequently asked questions
What does high creatinine mean?
A high creatinine usually reflects reduced kidney filtering, but it also rises with dehydration, high muscle mass, or a very high-protein or creatine intake — so it's read against your own baseline and your eGFR.
Can dehydration raise creatinine?
Yes — dehydration can transiently raise creatinine, which is one reason a single value is interpreted alongside the trend and your hydration.
Is high creatinine reversible?
It depends on the cause — dehydration-related rises often resolve with fluids, while a genuine decline in kidney function may not. A rising creatinine is worth discussing with your doctor.
This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.