Serum Creatinine
Creatinine is a waste product produced by normal muscle metabolism (breakdown of creatine phosphate). Your kidneys filter creatinine out of the blood and excrete it in urine at a fairly constant rate. When kidney function declines, creatinine accumulates in the blood, making it one of the earliest and most reliable indicators of kidney health.
Reference Ranges
Male
0.7 – 1.3
mg/dL
Female
0.6 – 1.1
mg/dL
Child
0.3 – 0.7
mg/dL
Ages 3–12
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
Low creatinine is usually not concerning and is common in people with low muscle mass (elderly, malnourished, or very lean individuals). Pregnancy also lowers creatinine due to increased kidney filtration. Very low values rarely indicate a medical problem.
What High Levels Mean
High creatinine signals impaired kidney function. Acute causes include dehydration, certain medications (NSAIDs, ACE inhibitors), or kidney infection. Chronic elevation suggests chronic kidney disease (CKD). A creatinine of 2.0+ mg/dL typically means significant kidney impairment.
Frequently Asked Questions
What is the relationship between creatinine and eGFR?
eGFR (estimated glomerular filtration rate) is calculated from your creatinine level, age, sex, and sometimes ethnicity. It provides a more standardized measure of kidney function. As creatinine rises, eGFR falls — they are inversely related.
Can exercise affect creatinine levels?
Intense exercise can temporarily raise creatinine because of increased muscle breakdown. This is usually mild and returns to normal within 24–48 hours. If you exercise heavily, mention it to your doctor when reviewing kidney function tests.
Does high creatinine always mean kidney disease?
Not always. Dehydration, high-protein diets, creatine supplements, certain medications, and intense exercise can temporarily raise creatinine. A single elevated reading needs to be confirmed with repeat testing and eGFR calculation.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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