Creatinine levels, explained
Creatinine is a muscle waste product cleared by the kidneys — the standard blood marker used to estimate kidney function.
What’s a normal Cr level?
Typical adult reference range, shown for orientation. Your report’s range may differ by lab, age, and sex — the analyzer uses your report’s own ranges when available.
What high and low Cr mean
A value outside the reference range is a flag, not a diagnosis. Here’s what each direction usually points to — and the most common causes.
High creatinine generally signals reduced kidney filtration, though dehydration, muscle mass, and certain medications also raise it.
- Acute or chronic kidney disease
- Dehydration or reduced blood flow to the kidneys
- High muscle mass or recent intense exercise
- Certain medications (NSAIDs, some antibiotics)
Low creatinine is usually not a concern and most often reflects low muscle mass rather than a kidney problem.
- Low muscle mass or older age
- Pregnancy (increased filtration)
- Prolonged illness or malnutrition
When a Cr result needs attention
A rising creatinine over time, or a high value with reduced urination, swelling, or fatigue, suggests declining kidney function and needs prompt assessment alongside eGFR.
Have your Cr number? Get the full picture.
Upload or paste your whole lab report and the free AI analyzer interprets every value at once — in context, not in isolation. No signup, no email, nothing stored.
Creatinine — frequently asked questions
- What does high creatinine mean?
- High creatinine usually means the kidneys are filtering less effectively, so this waste product builds up in the blood. But dehydration, high muscle mass, intense exercise, and some medications can also raise it. It is interpreted alongside eGFR, which converts creatinine into a kidney-function grade adjusted for age and sex.
- Can dehydration raise creatinine?
- Yes. Dehydration reduces blood flow to the kidneys and can temporarily raise creatinine without lasting kidney damage. Rehydrating and retesting often brings the value back down, which is why a single elevated result is usually confirmed.
- What is a normal creatinine level?
- Typical adult ranges are roughly 0.7–1.3 mg/dL for men and slightly lower for women, partly because of differences in muscle mass. Because the range is muscle-dependent, eGFR is the more meaningful measure of kidney function.
Related lab markers
- Hemoglobin A1c →HbA1c reflects your average blood sugar over roughly the past three months — the standard test for diagnosing and monitoring diabetes.
- ALT (Alanine Aminotransferase) →ALT is a liver enzyme released into the blood when liver cells are stressed or damaged — one of the most sensitive markers of liver health.
- Hemoglobin →Hemoglobin is the protein in red blood cells that carries oxygen — low hemoglobin defines anemia.
- All lab markers →Browse every biomarker guide in one place.
This page provides educational health information and does not replace professional medical advice, diagnosis, or treatment. Interpret any lab value with your clinician, who has your full medical context. For emergencies, contact emergency services.