The estimated glomerular filtration rate, or eGFR, is a calculated kidney function result that estimates how much blood your kidneys filter each minute. Most labs report it automatically when creatinine is measured in a blood test. A higher eGFR usually means better filtering capacity, while a lower eGFR can suggest chronic kidney disease, acute kidney injury, dehydration, medication effects, or another condition that is reducing kidney filtration.
An eGFR result is most useful when it is interpreted with your age, past results, urine albumin, blood pressure, diabetes status, medications, and symptoms. A single mildly low result does not always mean permanent kidney disease. Kidney function can change temporarily during illness, dehydration, heavy exercise, or after starting certain medicines. Repeating the test and checking urine albumin often gives a much clearer picture than focusing on one number alone.
- eGFR estimates kidney filtration from creatinine, and sometimes cystatin C, reported in mL/min/1.73 m².
- An eGFR of 90 or higher is generally normal, while 60–89 may be normal unless other kidney damage markers are present.
- An eGFR below 60 for at least 3 months is one major criterion for chronic kidney disease.
- CKD stages use eGFR ranges: G1 ≥90, G2 60–89, G3a 45–59, G3b 30–44, G4 15–29, and G5 below 15.
- Urine albumin testing is essential because kidney damage can be present even when eGFR is still normal.
- Seek urgent care for low eGFR with very low urine output, severe swelling, confusion, chest pain, shortness of breath, or high potassium symptoms.
Table of Contents
- What eGFR Measures
- How the eGFR Test Is Done
- Normal eGFR Results and CKD Stages
- What a Low eGFR Can Mean
- Why eGFR Can Be Inaccurate
- Follow-Up Tests After an Abnormal eGFR
- How to Protect Kidney Function
- When Low eGFR Needs Urgent Care
What eGFR Measures
eGFR estimates how well the kidneys are filtering waste and extra fluid from the blood. The “GFR” part stands for glomerular filtration rate. Glomeruli are tiny filtering units inside the kidneys. They let water and small waste products move out of the blood while keeping most blood cells and larger proteins in the bloodstream.
A measured GFR can be done with special injected or infused substances, but that process is time-consuming and not needed for most routine care. eGFR is the practical version. It uses a blood marker, usually creatinine, in an equation that also includes age and sex. Many laboratories now use the 2021 CKD-EPI creatinine equation, which does not include race.
Creatinine is a waste product made from normal muscle turnover. Healthy kidneys remove it from the blood. When kidney filtration falls, creatinine often rises, and the calculated eGFR falls. This relationship is why eGFR is usually reported with the creatinine blood test.
eGFR is reported as mL/min/1.73 m². The 1.73 m² part adjusts the result to a standard body surface area, which helps compare kidney filtration across people of different body sizes. In everyday use, most people focus on the number: 90, 75, 58, 42, 28, and so on.
eGFR reflects filtration, not every kidney function. Kidneys also regulate potassium, sodium, acid-base balance, blood pressure hormones, red blood cell signals, vitamin D activation, and fluid balance. A person can have a stable eGFR but still need other kidney-related tests, especially urine albumin, electrolytes, bicarbonate, blood pressure, and medication review.
How the eGFR Test Is Done
An eGFR test usually starts with a standard blood draw. The laboratory measures creatinine and calculates eGFR automatically. eGFR often appears on a basic metabolic panel, comprehensive metabolic panel, renal function panel, or kidney function panel. You may see it listed as eGFR, eGFRcr, eGFR creatinine, or estimated GFR.
Most people do not need to fast for eGFR alone. Fasting may be required if the same blood draw includes glucose, lipids, or other tests that your clinician wants measured under fasting conditions. Drinking a normal amount of water before the test is usually fine unless you were told to restrict fluids.
Because creatinine can shift slightly from recent diet and activity, it helps to avoid unusual conditions before a routine kidney check. A large meat-heavy meal, intense exercise, dehydration, or creatine supplements can affect creatinine in some people. These do not always create a major change, but they can matter when the result is near an important cutoff.
Some people also have cystatin C measured. Cystatin C is another blood marker used to estimate GFR. It is produced by many cells in the body and is less tied to muscle mass than creatinine. When creatinine-based eGFR may be misleading, a combined creatinine-cystatin C eGFR can give a more reliable estimate. This is especially useful when decisions depend on a precise kidney function estimate, such as confirming CKD stage, adjusting certain medicines, evaluating kidney donation, or clarifying mixed results. A related page on cystatin C and creatinine can help explain why the two estimates may not always match.
eGFR is not the same as creatinine clearance. Creatinine clearance usually uses a timed urine collection plus blood creatinine. It can be helpful in selected situations, but timed urine collections are easy to collect incorrectly. For most adults, eGFR is simpler and more commonly used.
Normal eGFR Results and CKD Stages
An eGFR of 90 or higher is generally considered normal or high kidney filtration. An eGFR of 60–89 is mildly decreased compared with young adult levels, but it does not automatically mean chronic kidney disease. Many older adults have an eGFR in this range without albumin in the urine or other signs of kidney damage.
Chronic kidney disease is usually defined by kidney abnormalities that last at least 3 months and have health implications. The abnormality may be a persistently low eGFR, albumin in the urine, blood in the urine from a kidney source, structural kidney changes on imaging, biopsy findings, genetic kidney disease, or a history of kidney transplant.
| CKD GFR Category | eGFR Range | General Meaning |
|---|---|---|
| G1 | 90 or higher | Normal or high filtration; CKD only if other kidney damage markers are present |
| G2 | 60–89 | Mildly decreased; CKD only if other kidney damage markers are present |
| G3a | 45–59 | Mild to moderate decrease in kidney function |
| G3b | 30–44 | Moderate to severe decrease in kidney function |
| G4 | 15–29 | Severe decrease in kidney function |
| G5 | Below 15 | Kidney failure range |
The stage is more informative when paired with urine albumin. Albumin is a blood protein that should usually stay in the bloodstream. When kidney filters are damaged, albumin can leak into the urine. The urine albumin-to-creatinine ratio, often called UACR or ACR, is one of the most important tests used with eGFR.
| Albumin Category | UACR Result | General Meaning |
|---|---|---|
| A1 | Less than 30 mg/g | Normal to mildly increased |
| A2 | 30–300 mg/g | Moderately increased |
| A3 | More than 300 mg/g | Severely increased |
A person with eGFR 72 and UACR 8 mg/g may have a very different risk pattern from someone with eGFR 72 and UACR 600 mg/g. The first result may be reassuring if stable. The second suggests significant kidney filter damage even though eGFR is above 60.
Trends also matter. An eGFR that falls from 95 to 78 over many years may reflect aging or stable mild reduction. An eGFR that falls from 95 to 58 in a few weeks needs prompt evaluation, even if the final number is not extremely low. Comparing eGFR with earlier lab results often gives more useful information than reading one result in isolation. This is one reason a broader kidney function blood test panel can be more helpful than a single marker.
What a Low eGFR Can Mean
A low eGFR means the kidneys appear to be filtering less blood than expected. The cause may be chronic, temporary, or mixed. The same eGFR number can mean different things depending on timing, symptoms, urine findings, and other blood results.
Chronic kidney disease
Chronic kidney disease is a common reason for persistently low eGFR. Diabetes and high blood pressure are leading causes. Other causes include glomerulonephritis, polycystic kidney disease, autoimmune disease, reflux or recurrent kidney infections, long-term urinary obstruction, kidney artery disease, and some inherited conditions.
CKD often has no symptoms in early stages. Many people with stage G3a CKD feel normal. Symptoms such as fatigue, itching, poor appetite, swelling, nausea, muscle cramps, trouble concentrating, and changes in urination are more likely as kidney function declines, but they are not specific to kidney disease.
Acute kidney injury
Acute kidney injury means kidney function has worsened over hours, days, or weeks. eGFR may drop suddenly, and creatinine may rise quickly. Common triggers include dehydration, severe infection, low blood pressure, heart failure flare, urinary blockage, kidney inflammation, major surgery, contrast exposure in vulnerable patients, or medication effects.
Acute kidney injury can be reversible, but it can also become dangerous quickly. A sudden eGFR drop deserves more urgent attention than a stable mildly low result.
Dehydration or low blood flow to the kidneys
Vomiting, diarrhea, poor fluid intake, heavy sweating, fever, or overdiuretic use can reduce blood flow to the kidneys. Creatinine may rise and eGFR may fall until fluid balance improves. This does not mean dehydration should be dismissed. In older adults, people with heart failure, people taking diuretics, and people taking blood pressure medicines that affect kidney blood flow, dehydration can cause serious kidney stress.
Medication effects
Some medicines can reduce eGFR temporarily, change creatinine handling, or cause kidney injury. Examples include nonsteroidal anti-inflammatory drugs such as ibuprofen and naproxen, some antibiotics, certain antivirals, contrast agents, chemotherapy drugs, calcineurin inhibitors, lithium, and high-dose diuretics. ACE inhibitors, ARBs, and SGLT2 inhibitors can cause an expected small early eGFR dip in some people, even while protecting kidneys over time in the right setting.
Medication changes should be handled with a clinician. Stopping a protective medicine because of a small expected eGFR change can sometimes do more harm than good.
Urinary blockage
A blockage can lower kidney function by backing up pressure into the kidneys. Causes include an enlarged prostate, kidney stones, tumors, ureter narrowing, or severe bladder retention. Symptoms may include trouble urinating, lower abdominal discomfort, flank pain, blood in urine, fever, or reduced urine output. Ultrasound or other imaging may be needed when obstruction is suspected.
Why eGFR Can Be Inaccurate
eGFR is an estimate, so it can be wrong in predictable situations. The most common issue is that creatinine depends partly on muscle mass. A muscular person may have a higher creatinine and lower calculated eGFR despite healthy filtration. A frail person, an older adult with low muscle mass, or someone with advanced liver disease may have a deceptively low creatinine and a falsely reassuring eGFR.
Creatinine-based eGFR can also be affected by diet and supplements. A large cooked meat meal can temporarily raise creatinine. Creatine supplements may increase measured creatinine or creatinine production. Intense exercise can raise muscle breakdown products. These factors matter most when the eGFR is close to a clinical cutoff.
Pregnancy is another special situation. Kidney filtration normally rises during pregnancy, and standard adult eGFR equations are not reliable for routine pregnancy kidney assessment. Clinicians usually interpret creatinine directly and use pregnancy-specific clinical context.
Very large or very small body size can also complicate interpretation. eGFR is indexed to 1.73 m² body surface area. For medication dosing, clinicians sometimes need a non-indexed kidney function estimate that better reflects actual body size. This is especially important for drugs with narrow safety margins.
Cystatin C can help when creatinine is unreliable, but cystatin C is not perfect. It may be influenced by thyroid disease, steroid use, inflammation, smoking, obesity, and some other non-GFR factors. The combined creatinine-cystatin C equation often performs better than either marker alone because the weaknesses of one marker may be balanced by the other.
Lab method and reporting also matter. Some labs report exact values above 60, while others may report “>60” or “>90.” If your lab only reports “>60,” you cannot use that result to track small changes in the normal or mildly reduced range. Ask for the exact value if trend tracking is important.
Follow-Up Tests After an Abnormal eGFR
A low eGFR should usually be confirmed and explained, not simply labeled. The next step depends on how low the result is, how fast it changed, and whether there are symptoms or other abnormal tests.
For a mildly low result, clinicians often repeat creatinine and eGFR after a period of time, especially if dehydration, recent illness, intense exercise, or medication changes may have affected the result. CKD usually requires evidence lasting at least 3 months, though treatment may start earlier when the pattern clearly suggests kidney disease.
Urine albumin-to-creatinine ratio is one of the most important follow-up tests. A normal UACR is reassuring, while persistent albuminuria can identify kidney damage even when eGFR is preserved. Urinalysis can also check for blood, casts, infection signs, glucose, specific gravity, and other clues.
A metabolic panel helps evaluate related blood chemistry. Potassium, bicarbonate or CO2, sodium, chloride, calcium, glucose, and BUN can show how kidney function is affecting fluid, electrolyte, and acid-base balance. A basic metabolic panel is often enough for routine follow-up, while a comprehensive metabolic panel adds liver proteins and liver enzymes.
Blood pressure measurement is essential. High blood pressure can cause CKD and can also result from CKD. Home blood pressure readings may reveal patterns that a single office reading misses.
Additional tests may include cystatin C, kidney ultrasound, urine protein-to-creatinine ratio, urine microscopy, diabetes testing, autoimmune markers, hepatitis testing, serum and urine protein electrophoresis, genetic testing, or kidney biopsy. These are not needed for every abnormal eGFR. They are chosen when the history, urine findings, age, family history, severity, or speed of change suggests a specific cause.
Bring a medication and supplement list to the visit. Include prescription medicines, over-the-counter pain relievers, antacids, vitamins, herbal products, protein powders, creatine, and bodybuilding supplements. Many kidney-related decisions depend on the full medication picture.
How to Protect Kidney Function
Protecting kidney function starts with treating the cause of the abnormal eGFR whenever possible. For many people, the largest gains come from controlling blood pressure, managing diabetes, reducing albuminuria, avoiding kidney-toxic exposures, and adjusting medicines safely.
Blood pressure control is one of the strongest kidney-protective steps. Many people with CKD benefit from ACE inhibitors or ARBs, especially when albuminuria is present. These medicines can slightly raise creatinine at first, so clinicians usually monitor creatinine and potassium after starting or increasing the dose.
Diabetes care matters because high blood sugar can damage kidney filters over time. A1c targets should be individualized, especially in older adults or people at risk for low blood sugar. SGLT2 inhibitors are now commonly used to reduce kidney and cardiovascular risk in many people with CKD, including some without diabetes, depending on eGFR, albuminuria, and other clinical factors.
Avoiding unnecessary NSAIDs can protect vulnerable kidneys. Occasional NSAID use may be acceptable for some people, but regular use can be risky in CKD, heart failure, dehydration, older age, or when combined with certain blood pressure medicines and diuretics. Acetaminophen may be safer for many people, but dose limits and liver health still matter.
Dietary changes depend on CKD stage, potassium, phosphorus, blood pressure, diabetes, and urine albumin. Many people benefit from moderating sodium intake, avoiding heavily processed foods, and eating a balanced pattern rich in appropriate whole foods. Protein intake should be individualized. Very high protein diets may stress kidneys in some CKD settings, while too little protein can worsen nutrition, especially in older adults or advanced disease.
Potassium advice should be based on blood results, not assumptions. Some people with CKD have normal potassium and do not need broad potassium restriction. Others develop high potassium, especially with lower eGFR or certain medicines. A detailed article on high potassium blood test results explains why potassium deserves careful follow-up when kidney function is reduced.
Medication dosing may need adjustment as eGFR falls. This includes some antibiotics, diabetes medicines, anticoagulants, seizure medicines, pain medicines, antivirals, gout medicines, and heart drugs. Dose changes should be individualized because underdosing can be harmful too.
Regular monitoring helps catch change early. People with stable mild CKD may need periodic eGFR and UACR checks. People with faster decline, higher albuminuria, high potassium, difficult blood pressure, or stage G4–G5 CKD usually need closer follow-up and often nephrology involvement.
When Low eGFR Needs Urgent Care
A low eGFR needs urgent care when it appears suddenly, is severe, or comes with symptoms that suggest acute kidney injury, dangerous electrolyte imbalance, fluid overload, infection, or urinary obstruction.
Get urgent medical help for very little or no urine, severe shortness of breath, chest pain, fainting, confusion, severe weakness, new irregular heartbeat, severe swelling, vomiting that prevents fluids, black or bloody stools, severe flank pain, fever with back pain, or inability to urinate despite bladder pressure.
High potassium can be especially dangerous because it can affect heart rhythm. Symptoms may include muscle weakness, palpitations, chest discomfort, lightheadedness, or fainting, but high potassium can also occur without symptoms. This is why potassium is often checked promptly when eGFR falls significantly.
An eGFR below 15 is in the kidney failure range, but the need for dialysis is not based on eGFR alone. Clinicians consider symptoms, potassium, acid-base balance, fluid overload, uremic complications, nutrition, urine output, and overall health. Some people with eGFR below 15 are monitored closely before dialysis starts, while others need urgent treatment because of complications.
Nephrology referral is commonly considered for eGFR below 30, rapidly falling eGFR, persistent high albuminuria, blood in the urine with protein, resistant high blood pressure, uncertain cause, inherited kidney disease, recurrent kidney stones with kidney damage, or major electrolyte problems. Referral does not mean dialysis is imminent. Often it means there is an opportunity to slow decline, clarify the diagnosis, and plan ahead.
References
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease 2024 (Guideline)
- Executive summary of the KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease: known knowns and known unknowns 2024 (Guideline)
- KDOQI US Commentary on the KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD 2025 (Commentary)
- Estimated GFR (eGFR) Test: Kidney Function Levels, Stages, and What to Do Next | National Kidney Foundation 2026 (Official Patient Education)
- Chronic Kidney Disease Tests & Diagnosis – NIDDK 2016 (Official Government Page)
Disclaimer
This article is for general education about eGFR testing and kidney function. It cannot diagnose kidney disease, acute kidney injury, medication toxicity, or the cause of an abnormal result. Always review abnormal eGFR, creatinine, urine albumin, potassium, and related symptoms with a qualified healthcare professional, especially if the change is new, severe, or worsening.
