eGFR — how to read your estimated kidney function, beyond "normal" or "low"

Q: Is an eGFR of 60–89 kidney disease?

Not by itself. An eGFR in the 60–89 range without any marker of kidney damage (like albuminuria) is often just normal aging. Chronic kidney disease is diagnosed when eGFR is persistently below 60, or when a damage marker is present alongside a higher eGFR. Context and the urine test decide.

Q: Why did my eGFR change without any symptoms?

Several harmless reasons are possible: dehydration on the day of the draw, a recent high-protein meal or intense workout, or the lab switching to the 2021 race-free CKD-EPI equation. A single change, especially a small one, is best confirmed with a repeat test rather than acted on immediately.

Q: What's the most important test to add to eGFR?

The urine albumin-to-creatinine ratio (uACR). It detects protein leaking into the urine — frequently the earliest sign of kidney damage and something eGFR alone can miss. KDIGO guidelines stage kidney health using eGFR and albuminuria together.

Q: Can I improve my eGFR?

You can often slow or stabilize decline by controlling blood pressure and blood sugar, avoiding kidney-stressing medications like frequent NSAIDs, staying well hydrated, and following a kidney-appropriate diet. Whether a specific number can rise depends on the cause. This should be managed with your clinician.

Q: Do I need to fast for a creatinine/eGFR test?

Fasting isn't strictly required for creatinine, but a very high-protein meal or creatine supplements shortly before the draw can transiently raise creatinine and lower the estimate. It's often ordered with fasting labs, so follow the instructions for the full panel.

Paired condition: Type 2 diabetes labs

Quick answer

eGFR (estimated glomerular filtration rate) estimates how well your kidneys filter blood, calculated from your blood creatinine plus age and sex. It's the headline kidney-function number, but a single eGFR is easy to over-read: it can dip temporarily from dehydration, and chronic kidney disease is diagnosed on *persistence* (≥ 3 months) plus a urine test — not one blood draw. The urine albumin-to-creatinine ratio is the piece most people are missing.

Reference ranges and interpretation

Value / population	Classification	What it means
≥ 90 mL/min/1.73m²	G1 — normal or high	Normal filtration. Only counts as kidney disease if there's also a marker of damage (e.g., albuminuria).
60 – 89	G2 — mildly decreased	Often age-related; again, only 'disease' if a damage marker is present.
45 – 59	G3a — mild-to-moderate	The threshold where CKD is typically diagnosed even without other findings.
30 – 44	G3b — moderate-to-severe	Warrants closer monitoring and often nephrology input.
15 – 29	G4 — severely decreased	Advanced CKD; nephrology management.
< 15	G5 — kidney failure	Kidney failure; dialysis or transplant considerations.

eGFR stages (G1–G5) are from the KDIGO framework. A key nuance: eGFR 60–89 alone, without any marker of kidney damage, is not chronic kidney disease — it can simply reflect normal aging.

What eGFR is — and why creatinine alone isn't enough

Your kidneys filter waste from the blood. Creatinine is one such waste product, and when filtration slows, creatinine rises. eGFR converts your creatinine into an estimate of filtration rate using a validated equation (the CKD-EPI equation) that also factors in age and sex.

Why not just read creatinine? Because the same creatinine value means very different things in a 25-year-old versus a 75-year-old, and in a large muscular person versus a small one. eGFR standardizes for age and sex to make the number comparable. It's still an estimate — it can be thrown off in people with unusually high or low muscle mass.

What a single low eGFR does and doesn't mean

One low eGFR is not a diagnosis. Filtration temporarily drops with dehydration, certain medications (NSAIDs, some blood-pressure drugs), and acute illness. That's why chronic kidney disease requires the abnormality to persist for at least 3 months.

Equally important: eGFR is only half of the kidney picture. The other half is the urine albumin-to-creatinine ratio (uACR), which detects protein leaking into the urine — often the earliest sign of kidney damage, sometimes present while eGFR still looks normal. KDIGO stages kidney disease on both eGFR (G) and albuminuria (A) together. If you've only ever had eGFR checked, the urine test is the missing piece.

The 2021 race-free equation — why your number may have changed

Older creatinine-based eGFR equations included a race coefficient that raised the estimate for Black patients. In 2021, a refitted CKD-EPI equation removed race from the calculation to provide a single equation for everyone. As labs adopted it, some people's reported eGFR shifted even though their kidneys hadn't changed — purely because the formula changed.

The most accurate estimates combine creatinine with cystatin C, a second filtration marker that isn't affected by muscle mass. If your creatinine-based eGFR is borderline or you have atypical muscle mass, a cystatin C–based eGFR can clarify the true value.

What to look at alongside eGFR

A complete kidney assessment includes:

- Urine albumin-to-creatinine ratio (uACR) — the damage marker eGFR misses; the single most important companion test
- Cystatin C — a muscle-independent filtration marker for confirming borderline eGFR
- Blood pressure — both a cause and a consequence of kidney disease
- HbA1c / glucose — diabetes is the leading cause of CKD worldwide
- Electrolytes (potassium, bicarbonate) and phosphate — affected as function declines
- Trend over time — the slope of eGFR matters more than any single value

Because diabetes and high blood pressure are the top drivers of kidney disease, eGFR is best read alongside your metabolic and cardiovascular labs.

Phi Longevity reads every marker on every lab you upload — together, against your history, against optimal ranges, and across time. The integrated picture tells you what a single number can't.

Start with my labs →

Frequently asked questions

Is an eGFR of 60–89 kidney disease?

Not by itself. An eGFR in the 60–89 range without any marker of kidney damage (like albuminuria) is often just normal aging. Chronic kidney disease is diagnosed when eGFR is persistently below 60, or when a damage marker is present alongside a higher eGFR. Context and the urine test decide.

Why did my eGFR change without any symptoms?

Several harmless reasons are possible: dehydration on the day of the draw, a recent high-protein meal or intense workout, or the lab switching to the 2021 race-free CKD-EPI equation. A single change, especially a small one, is best confirmed with a repeat test rather than acted on immediately.

What's the most important test to add to eGFR?

The urine albumin-to-creatinine ratio (uACR). It detects protein leaking into the urine — frequently the earliest sign of kidney damage and something eGFR alone can miss. KDIGO guidelines stage kidney health using eGFR and albuminuria together.

Can I improve my eGFR?

You can often slow or stabilize decline by controlling blood pressure and blood sugar, avoiding kidney-stressing medications like frequent NSAIDs, staying well hydrated, and following a kidney-appropriate diet. Whether a specific number can rise depends on the cause. This should be managed with your clinician.

Do I need to fast for a creatinine/eGFR test?

Fasting isn't strictly required for creatinine, but a very high-protein meal or creatine supplements shortly before the draw can transiently raise creatinine and lower the estimate. It's often ordered with fasting labs, so follow the instructions for the full panel.

References

All citations verified against PubMed / publisher of record (see note below for this page's verification date).

1.Levey AS, Stevens LA, Schmid CH, et al. (CKD-EPI). (2009). A New Equation to Estimate Glomerular Filtration Rate. Annals of Internal Medicine. 150(9):604-612. — The CKD-EPI creatinine equation used to compute eGFR from creatinine, age, and sex.PubMed →DOI →
2.Inker LA, Eneanya ND, Coresh J, et al. (2021). New Creatinine- and Cystatin C–Based Equations to Estimate GFR without Race. New England Journal of Medicine. 385(19):1737-1749. — The 2021 race-free CKD-EPI equations and the value of adding cystatin C — basis for that section.PubMed →DOI →
3.Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. (2024). KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney International. 105(4S):S117-S314. — Source for the G1–G5 staging, the ≥ 3-month persistence requirement, and the eGFR-plus-albuminuria (G+A) framework.PubMed →DOI →

eGFR is an estimate and can be less accurate in people with atypical muscle mass; a cystatin C–based estimate can help in those cases. Chronic kidney disease is defined by persistence (≥ 3 months) and staged with albuminuria, not by a single eGFR. Every link opens the PubMed abstract or publisher's DOI landing page in a new tab. All citations verified vs PubMed / publisher of record 2026-07-18.

By Steve Pinedo

Co-founder, Phi Longevity

Last updated: 2026-07-18

Steve Pinedo is the Co-founder of Phi Longevity, the AI application that turns a confusing stack of lab reports, wearable data, and clinical notes into a single, integrated picture of your health. He started Phi Longevity to make proactive health and wellness far easier to achieve. He realized how difficult it was for clients to manage their own care, records and coordination so he assembled a comprehensive M.D. led clinical team behind the platform, packaging the proactive-care experience that delivered measurable outcomes (lower triglycerides, reduced body fat, improved LDL, balanced hormones, relief from long-running autoimmune conditions) for any patient with a complicated lab to use now with an application. More about Phi Longevity →

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