All articles · LAB RESULTS · 28 JUNE 2026

Kidney function explained: creatinine and eGFR blood test results

Creatinine and eGFR are two of the most common ways a blood test checks on your kidneys, and they often appear right next to each other on your report. This guide explains what each one measures, how they fit together, and how to read a high or low result calmly and in context.

Health information, not medical advice. This article is for education and information only. Prova does not diagnose, treat, or replace a conversation with a qualified healthcare professional. Normal ranges and how each result is interpreted vary by individual and lab. Always discuss your blood test results with your doctor or clinician. For emergencies, contact your local emergency services.

What your kidneys do

Your two kidneys are quiet, full-time workers. Each one is packed with about a million tiny filters that clean your blood, around the clock, without you noticing. As blood passes through, the kidneys pull out waste products and extra fluid, which leave the body as urine, while keeping the things you need, like protein and most minerals, in your bloodstream.

That filtering does more than remove waste. Your kidneys also help balance the water and salts in your body, keep blood pressure steady, and signal your body to make red blood cells. Because they touch so many systems, a simple blood test that hints at how well they are filtering can tell a doctor a lot, which is why creatinine and eGFR show up on so many routine panels.

What creatinine is

Creatinine is a waste product. Your muscles use a compound called creatine for energy, and as they work, they steadily produce creatinine as a byproduct. It travels in your blood to the kidneys, which filter it out and send it into the urine.

Here is why that makes creatinine useful: your muscles produce it at a fairly steady rate, so the amount left in your blood mostly reflects how well your kidneys are clearing it. If the kidneys are filtering well, blood creatinine stays low. If filtering slows, creatinine tends to build up. It is usually reported in milligrams per deciliter (mg/dL) in the United States and India, or micromoles per liter (umol/L) in many other countries.

One important nuance: because creatinine comes from muscle, your level depends partly on your body. People with more muscle mass naturally run a little higher, and people with less muscle run a little lower. That is one reason the number is rarely read on its own.

What eGFR is

eGFR stands for estimated glomerular filtration rate. In plainer terms, it is an estimate of how fast your kidneys are filtering your blood. It is not measured directly; instead, a lab calculates it from your creatinine result, adjusting for factors such as your age and sex.

Think of creatinine as the raw reading and eGFR as the translated score. A higher eGFR means faster, more effective filtering, the opposite direction from creatinine, where lower is generally better. The result is reported in milliliters per minute per 1.73 m² of body surface area (mL/min/1.73 m²), but most people simply read it as a single number where higher is better.

Because eGFR is built from creatinine, anything that throws off creatinine, such as unusual muscle mass or a recent creatine supplement, can also nudge the eGFR. That is why doctors treat it as one helpful indicator among several, not a verdict.

What your numbers mean

Normal ranges describe what is typical for most people; they are not a judgment on any one person, and they vary by lab. With that in mind, here is how kidney results are commonly grouped for adults. The eGFR ranges below line up with the stages doctors use to describe kidney function:

Creatinine, typical range: often around 0.7 to 1.3 mg/dL for men and 0.6 to 1.1 mg/dL for women, with the exact range set by your lab. Higher muscle mass can push the top end up without signaling a problem.
eGFR 90 or above: commonly described as typical filtering for healthy kidneys.
eGFR 60 to 89: a mild reduction. On its own, with no other signs, this is frequently still considered within a normal range, and it is common with age.
eGFR below 60, sustained over three months: the level at which doctors start to look more closely at kidney function. A doctor interprets this alongside creatinine, urine tests, blood pressure, and your history, never from a single number.

It helps to hold two ideas apart. "Normal" means inside the lab's usual range. "Healthy for you" is more personal: eGFR drifts down gradually as we age, so a value that is typical for a 70-year-old might prompt a closer look in a 30-year-old. Putting your number in that personal context is exactly what a conversation with your clinician adds.

Why trends matter more than single values

A single creatinine or eGFR reading is a snapshot, and snapshots can mislead. Creatinine in particular moves with everyday factors: dehydration can raise it, a big protein meal or a creatine supplement can lift it briefly, and intense exercise the day before can do the same. Some medications affect it too. Any of these can make one reading look higher than your true baseline.

This is why doctors pay attention to the direction of travel across several tests, not one isolated value. A result that sits steadily in the same place over a few panels is reassuring, even if it is at the edge of a range. A clear, sustained drop in eGFR or rise in creatinine across more than one test is the pattern worth a focused conversation. When you compare your own results over time, look at the trend and the size of the change rather than fixating on a single point.

Signs that filtering may be slower

Early changes in kidney function often cause no symptoms at all, which is part of why blood tests are so useful, they can flag a change before you would feel anything. When symptoms do appear, they are general and can have many causes unrelated to the kidneys, so they are clues to mention rather than proof of a problem. Things people sometimes notice include:

Tiredness or low energy that is hard to explain.
Swelling (puffiness) in the ankles, feet, or around the eyes, which can be linked to fluid balance.
Changes in urination, such as needing to go more or less often, especially at night, or foamy-looking urine.
Poor appetite, nausea, or trouble concentrating in some cases.

None of these on its own points to a kidney issue, and many have far more common explanations. If you notice them, especially together or persisting, they are worth raising with your doctor, who can decide whether any testing makes sense.

What to discuss with your doctor

If your creatinine or eGFR is flagged, the most useful next step is a conversation, not a self-directed plan. Helpful, general topics to raise, none of which is a treatment or prescription, include:

Hydration. Whether dehydration could have affected the reading, and what steady, sensible fluid intake looks like for you.
Your context before the test. A recent high-protein meal, a creatine supplement, or hard exercise, all of which can nudge creatinine and are worth mentioning.
Medications and supplements. Which of the things you take are cleared by the kidneys, and whether any need a closer look.
Related tests. Whether a urine test, blood pressure check, or repeat blood panel would help complete the picture.
Monitoring. How often to re-check, and what trend would or would not be meaningful for you.
Diet. Whether any dietary changes are appropriate, decided with your doctor or a dietitian rather than on your own.

Key takeaways

Creatinine is a muscle waste product your kidneys filter out; eGFR is an estimate of how fast they are filtering, calculated from creatinine.
Lower creatinine and higher eGFR generally point to better filtering; an eGFR of 90 or above is commonly described as typical, and below 60 sustained over three months is when doctors look more closely.
One reading can shift with dehydration, a protein meal, a creatine supplement, exercise, or medication, so trends across several tests matter more than a single value.
Early changes often cause no symptoms, and decisions about diet, protein, and monitoring belong with your doctor, not a self-directed plan.

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How Prova fits in

Prova reads your lab report and explains each result, including creatinine and eGFR, in plain language, then lets you ask follow-up questions grounded in your own results. It is built to help you understand your report and prepare for a conversation with your doctor, not to replace one. Prova does not diagnose, and it is not yet available in the app stores; you can join early access today.

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Common questions

What causes high creatinine?

Creatinine can rise for many reasons, and not all of them mean a kidney problem. Common temporary causes include dehydration, a recent high-protein meal or creatine supplement, intense exercise, and certain medications. Because creatinine comes from muscle, people with more muscle mass tend to run a little higher at baseline. A truly elevated result that holds up on a repeat test, especially alongside a lower eGFR, is the kind a doctor looks into further. One high reading is a reason to follow up, not a diagnosis.

Do I need to restrict protein if my creatinine is high?

Not on your own. Protein is an important part of a healthy diet, and cutting it back without guidance can do more harm than good. Some people with reduced kidney function are advised by their doctor or a dietitian to adjust protein intake, but that decision is personalised to your results and overall health. A very high-protein meal or a creatine supplement shortly before a blood draw can nudge a single reading up, which is worth mentioning to your clinician, but routine protein restriction is a conversation to have with your doctor, not a step to take alone.

How often should kidney function be tested?

For many adults, creatinine and eGFR are checked as part of a routine periodic blood panel, often once a year. If you have conditions that affect the kidneys, such as high blood pressure or diabetes, or you take medications that the kidneys clear, your doctor may suggest checking more often. The right interval depends on your results and health history, so your clinician sets the schedule that fits you. Trends across several tests are usually more informative than any single value.

What is a normal eGFR?

An eGFR of about 90 or above is commonly described as typical for healthy kidneys, and many labs report any value at or above 60 with no other signs as normal. eGFR naturally declines a little with age, so a value in the 60s can be perfectly normal for an older adult. Because eGFR is an estimate calculated from creatinine, doctors read it alongside the actual creatinine value, a urine test, and your overall picture rather than treating the number in isolation.