eGFR & Creatinine —
what the numbers
tell you about your kidneys.
Your eGFR came back at 58 and you're worried about kidney disease. Before assuming the worst — eGFR varies significantly with age and muscle mass, and a single result rarely tells the full story.
Dr. James Okafor, MD, PhD
Internal Medicine, Metabolic Disease ·
The essentials — before you read the full guide below.
eGFR vs Creatinine
eGFR is calculated from creatinine, age, and sex. It's more useful than creatinine alone because creatinine varies greatly by muscle mass — an eGFR of 60 means the same thing in different body types.
CKD staging
eGFR ≥90 = normal. 60–89 = mildly reduced. 30–59 = moderately reduced. 15–29 = severely reduced. <15 = kidney failure. Staging requires two readings 3+ months apart.
One result isn't enough
CKD is only diagnosed when eGFR is persistently low — two readings below 60 more than 3 months apart. A single low eGFR may reflect temporary dehydration or illness.
eGFR declines with age
A healthy 80-year-old may have an eGFR of 55–65 with perfectly functioning kidneys for their age. Age-adjusted interpretation matters.
Reference Ranges
What does your number
actually mean?
Use the interactive slider below, or read the range cards for a full clinical breakdown.
Kidney Function Tests (eGFR & Creatinine) Reference Ranges
mL/min/1.73m² (eGFR)Enter your result
Drag to see what your Kidney Function Tests (eGFR & Creatinine) means
The Science
How kidneys filter your blood and why eGFR matters
Your kidneys filter approximately 180 litres of blood per day through ~1 million filtering units called nephrons. eGFR estimates how efficiently this filtering system is working — expressed as the volume filtered per minute per standard body surface area.
180 litres filtered per day
Each kidney contains ~500,000 nephrons. Together they filter 125 mL/minute — about 180 litres per day. Only 1–2 litres is excreted as urine; the rest is reabsorbed.
Creatinine is the filtration marker
Creatinine is a waste product of muscle metabolism freely filtered by the kidneys. When filtration falls, creatinine rises. eGFR is calculated from creatinine, age, and sex using the CKD-EPI 2021 formula.
CKD is symptom-free until Stage 4–5
The kidneys have significant reserve — symptoms typically don't appear until 70–80% of function is lost. Blood test monitoring is the only way to detect early CKD.
When to Test
Signs your doctor will
order this test
These are the most common reasons a Kidney Function Tests (eGFR & Creatinine) test is requested — from symptoms to routine screening.
Swelling in legs, ankles, or feet
Oedema is a late sign of kidney disease — caused by failure to regulate sodium and water balance.
Late signFoamy or bubbly urine
Persistent foam in urine indicates proteinuria — protein leaking into urine, an early damage marker.
Early damage signNocturia (nighttime urination)
Waking multiple times to urinate is an early sign of reduced kidney concentrating ability.
Early signFatigue and decreased concentration
Accumulation of waste products (uraemia) causes fatigue, brain fog, and decreased appetite — typically in Stage 4–5 CKD.
Late signDiabetes or hypertension
Diabetes is the leading cause of CKD worldwide; hypertension is second. Both require annual kidney function monitoring.
Screening essentialNSAID or contrast dye use
NSAIDs (ibuprofen, naproxen) and intravenous contrast agents can cause acute kidney injury. eGFR should be checked in at-risk patients.
Drug monitoringTesting Schedule
How often should
you get tested?
Frequency depends on your current health status and your doctor's guidance.
Healthy adults
Included in routine metabolic panel. Annual creatinine and eGFR recommended from age 50 by most guidelines.
Diabetes or hypertension
Both conditions directly damage kidney filtration units. Annual eGFR and urine albumin-to-creatinine ratio (UACR) are standard of care.
CKD Stage 3 or higher
Monitoring frequency increases with disease severity. Stage 3b and above require nephrology co-management.
Single low eGFR
A single low eGFR must be confirmed by a second measurement 3+ months later before CKD is diagnosed.
If Your Result Is Abnormal
How to protect kidney function
CKD progression can be significantly slowed — and sometimes halted — with targeted interventions, especially in early stages.
Adequate hydration
Mild dehydration chronically stresses kidneys. 2–3 litres of water per day supports filtration. Avoid chronic NSAID use — it reduces blood flow to kidneys.
Protective daily habitControl blood pressure & glucose
Keeping BP below 130/80 mmHg and HbA1c below 7% are the two most powerful interventions for slowing CKD progression — better than any medication alone.
Strongest protective factorsLow-protein diet (Stage 3+)
Reducing dietary protein to 0.6–0.8g/kg/day reduces the kidney's filtration load and slows GFR decline by 30–40%. Always done under dietitian supervision.
−30–40% GFR decline rateSGLT2 inhibitors (for diabetic CKD)
Empagliflozin and dapagliflozin have Level 1 evidence for reducing CKD progression and cardiovascular events in diabetic kidney disease.
Level 1A evidence