Understanding Creatinine and eGFR
You get your labs back. Everything looks normal — or so the portal tells you. But you have never actually had anyone explain what your creatinine means, what eGFR measures, or whether the number you are looking at should concern you.
This is one of the most common gaps in preventive kidney care. The tests exist. The results are being generated. But patients are left reading numbers without context — and context is everything.
What Creatinine Actually Measures
Creatinine is a waste product. It is produced naturally by your muscles as they metabolize energy, and it is filtered out of your blood by your kidneys and excreted in your urine.
When the kidneys are functioning well, creatinine is cleared efficiently and blood levels stay relatively stable. When kidney function declines, creatinine can begin to accumulate — and blood levels rise.
Here is where it gets important: creatinine alone does not tell the full story.
Muscle mass, body size, age, sex, hydration status, and overall health all influence creatinine levels. A young, muscular person may have a higher creatinine than an older, smaller person — even if their kidney function is identical. A result flagged as "normal" for one person may deserve closer attention in another.
This is why creatinine should never be interpreted in isolation.
What eGFR Tells You — and What It Doesn't
Estimated glomerular filtration rate — eGFR — is a more useful number. It uses creatinine along with age, sex, and other factors to estimate how well your kidneys are actually filtering your blood, expressed as a rate in milliliters per minute.
A general reference point:
Above 60: Often considered within normal range, though trends matter
45–59: Mild to moderate reduction in kidney function
30–44: Moderate to severe reduction — warrants close monitoring
Below 30: Severe reduction — specialist involvement is important
But these ranges are a starting point, not a verdict. A single eGFR reading is far less informative than a trend over time. Kidney function naturally declines slightly with age. A gradual, stable decline looks very different from a rapid or unexpected drop — and that difference matters clinically.
A mildly reduced eGFR does not automatically mean someone has advanced kidney disease. And a normal eGFR does not always mean the kidneys are perfectly healthy, particularly when other risk factors are present.
The Test Most People Have Never Had
If eGFR is one piece of the puzzle, urine albumin is another — and it is one of the most underused tools in preventive kidney care.
Urine albumin measures small amounts of protein leaking into the urine. Healthy kidneys keep protein in the bloodstream where it belongs. When they are under stress or beginning to sustain damage, protein can start to escape.
What makes this test so valuable is timing. Urine albumin can become abnormal before eGFR declines — meaning it can signal kidney stress earlier than the standard blood test alone. For patients with high blood pressure, diabetes, or cardiovascular disease, this test is not optional. It is essential.
If you have never been tested for urine albumin, ask for it.
What You Should Do With This Information
Labs are data. Data needs interpretation. And interpretation requires context — your history, your other conditions, your medications, your lifestyle, and the trend of your results over time.
One abnormal value is a reason to pay attention, not panic. One normal value is not a reason to stop looking.
At your next appointment, ask:
What is my current eGFR, and how has it changed over the past few years?
Has my urine been tested for albumin or protein?
Given my history, are these results something we should monitor more closely?
You do not need a medical degree to be an informed participant in your own kidney health. You just need the right questions — and a clinician willing to answer them honestly.
Aurius Health is a concierge telemedicine practice specializing in cardiovascular-kidney-metabolic (CKM) health. I work with patients who want proactive, connected care — not fragmented management of separate conditions. Learn more at auriushealth.com.