What is serum creatinine?

Serum creatinine is a blood test that measures the amount of creatinine, a waste product produced by your muscles. It is one of the most widely used markers of kidney function, because your kidneys are responsible for removing creatinine from the blood and excreting it through urine.

When your kidneys are working properly, they keep the level of creatinine in your blood within a healthy range. If your serum creatinine level is higher than normal, it may mean that your kidneys are not filtering waste efficiently.

Typical normal ranges for serum creatinine are:

• 0.6 to 1.2 mg/dL for men
• 0.5 to 1.1 mg/dL for women

These values can vary slightly depending on age, body size, muscle mass, and the laboratory performing the test. People with more muscle may naturally have higher levels, while elderly individuals or those with less muscle mass may have lower levels.

Serum creatinine is often used to calculate your estimated glomerular filtration rate (eGFR), which provides a more precise assessment of how well your kidneys are filtering blood. eGFR takes into account your creatinine level, age, sex, and sometimes race.

A rising creatinine level may indicate:

• Acute kidney injury (AKI)
• Chronic kidney disease (CKD)
• Dehydration
• Blockage in the urinary tract
• Side effects from medications

It is important to interpret creatinine levels in context. For example, a temporary spike might result from intense exercise, a high-protein meal, or certain medications. However, if levels stay elevated or continue to rise, further evaluation is usually needed.

Regular testing of serum creatinine helps detect kidney problems early—even before symptoms appear—and plays a key role in monitoring existing kidney conditions.

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