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How to Read Kidney Function Numbers: Creatinine and eGFR

Here is what creatinine and eGFR results on a lab report actually mean, and how to interpret them.

  1. What creatinine is

    Creatinine is a waste product left over from muscles using energy, and it is normally filtered out of the blood by the kidneys and excreted in urine. When kidney function declines, the kidneys filter out less of it, so creatinine builds up and its blood concentration rises.

  2. Typical creatinine reference range

    Reference ranges vary somewhat by lab, but a common range is roughly 0.7-1.3 mg/dL (about 62-115 micromol/L) for adult men and 0.6-1.1 mg/dL (about 53-97 micromol/L) for adult women. Men generally have a higher reference range mainly because they tend to have more muscle mass.

  3. What eGFR is

    eGFR, or estimated glomerular filtration rate, combines the creatinine level with age, sex, and sometimes other factors into a single estimate of how well the kidneys are filtering blood. It is generally considered a more complete picture of kidney function than creatinine alone.

  4. What different eGFR levels mean

    As a general guide, an eGFR of 90 or above is considered normal, and 60-89 indicates a mild decline. A value under 60 that persists for three months or longer can suggest chronic kidney disease, and the lower the number, for example under 30, the more significant the reduction in kidney function.

  5. Factors that can affect the numbers

    Higher muscle mass, a high-protein meal shortly before testing, significant dehydration, and certain medications can all temporarily raise creatinine levels. Because of this, a single abnormal result usually is not treated as a diagnosis on its own; repeat testing is the more common approach.

  6. What to do if a result is abnormal

    If creatinine or eGFR falls outside the reference range, it is generally recommended to also check a urine test, for protein, for example, and, if needed, follow up with a nephrologist to investigate the cause. Any specific interpretation or management plan should always be discussed with a healthcare provider.

eGFR already accounts for age and sex

Looking at creatinine alone can be misleading because of natural differences in muscle mass between people, which is why lab reports typically also calculate an age- and sex-adjusted eGFR alongside it. It is also normal for eGFR to decline gradually with age, which is worth keeping in mind when interpreting a result.

General information, not a diagnosis

This page explains commonly used reference ranges and general concepts to help you understand a lab report, and it is not a substitute for a medical diagnosis. If a report recommends a follow-up test or referral, it is worth taking that recommendation seriously and discussing next steps with a doctor.

Frequently Asked Questions

I exercise heavily. Can that make my creatinine look high?

Yes. Higher muscle mass, or intense exercise shortly before a test, can temporarily raise creatinine. Because of factors like this, doctors typically confirm an abnormal result with repeat testing rather than acting on a single number.

My eGFR came back between 60 and 89. Do I need to see a doctor right away?

That range is generally classified as a mild decline, and the usual first step is lifestyle attention and monitoring rather than immediate treatment. That said, if it persists or you have other risk factors, following up with a kidney specialist can be worthwhile.