Understanding Your eGFR Test Result

What Is eGFR and What Does It Measure?

Your kidneys act as a continuous filtration system, removing waste products and excess fluid from your blood around the clock. eGFR — estimated Glomerular Filtration Rate — is the number that tells your doctor how efficiently that filtration is happening. It is calculated from a standard blood test measuring creatinine (a waste product from muscle breakdown), combined with your age, sex, and sometimes ethnicity.

The result is expressed in millilitres per minute per 1.73 square metres of body surface area (mL/min/1.73m²). Think of it as the volume of blood your kidneys can clean every minute. A healthy adult typically has an eGFR above 90. The number naturally declines slowly with age — a 75-year-old may have an eGFR of 65 to 70 with perfectly healthy kidneys — which is why your doctor interprets the result alongside your symptoms, trends, and other test results rather than the number alone.

eGFR is not a diagnosis in itself. It is a screening indicator that flags when kidney function may need closer attention. A single low reading may reflect dehydration, a recent illness, or a heavy protein meal before the test. A persistently low reading across two or more tests taken at least 90 days apart is what defines chronic kidney disease (CKD).

Understanding the eGFR Stages — G1 to G5

Kidney disease is classified into five stages (G1 to G5) based on eGFR level. These stages guide your doctor’s decisions about monitoring frequency, medication, and when to refer to a specialist.

• G1 (eGFR 90+): Normal or high kidney function. If protein is detected in your urine, monitoring may still be recommended even with a normal eGFR.
• G2 (eGFR 60–89): Mildly reduced. Often age-related. No specific treatment, but annual monitoring is advised if other risk factors are present.
• G3a (eGFR 45–59) and G3b (eGFR 30–44): Moderately reduced. Your GP will likely refer you to a nephrologist. Medication review, blood pressure control, and dietary changes become important.
• G4 (eGFR 15–29): Severely reduced. Specialist-led care. Preparation for kidney replacement therapy (dialysis or transplant) begins at this stage.
• G5 (eGFR below 15): Kidney failure. Dialysis or transplantation is required.

Most people referred to a nephrologist are at G3 or above. If your eGFR has declined significantly over a short period — even if it remains above 60 — your GP may refer you sooner, because the rate of change matters as much as the absolute number.

What Causes a Low eGFR?

The two most common causes of a low or declining eGFR are diabetes and hypertension. Together, they account for the majority of CKD cases globally. Poorly controlled blood sugar damages the tiny blood vessels (glomeruli) inside the kidneys over years. Uncontrolled high blood pressure applies sustained mechanical pressure to those same vessels, accelerating the damage.

Other causes include autoimmune conditions (lupus nephritis, IgA nephropathy), recurrent urinary tract infections, long-term use of anti-inflammatory medications (NSAIDs like ibuprofen or naproxen), certain antibiotics, contrast dye used in imaging, and hereditary conditions such as polycystic kidney disease.

Temporary causes of a low reading — not true CKD — include dehydration, acute illness, strenuous exercise the day before the test, or a very high-protein meal. If your result surprises your doctor, they will usually repeat the test in four to eight weeks before acting on the finding.

What Happens If Your eGFR Is Low?

What your doctor does next depends on your eGFR stage, whether it is declining, and whether protein or blood is present in your urine alongside the low reading. At G2 to G3a with no other abnormalities, most GPs will monitor with a repeat eGFR and urine test every six to twelve months and focus on managing the underlying causes — blood pressure, blood sugar, and medications.

At G3b and below, a referral to a nephrologist (kidney specialist) is standard practice. The nephrologist will investigate the underlying cause more thoroughly, review all medications for kidney impact, and begin planning long-term management. In Singapore, this typically occurs through the specialist outpatient clinic at restructured hospitals. In Australia, a Medicare-funded nephrology referral is arranged through your GP. In the US, specialist referral depends on your insurance coverage — check your plan before booking.

Medications commonly reviewed or adjusted when eGFR is low include metformin (paused below eGFR 30), NSAIDs (stopped entirely), certain antibiotics, and blood pressure medications that protect the kidneys specifically — ACE inhibitors and ARBs are often the preferred choice for CKD patients with hypertension or diabetes.

Questions to Ask Your Doctor About Your eGFR Result

Whether you are seeing your GP or a nephrologist, prepare these questions to get maximum clarity from the appointment:

• Is this a single reading or a trend — has my eGFR been declining over time?
• Do I also have protein or blood in my urine, and what does that mean for my diagnosis?
• What is causing my eGFR to be low — which underlying condition should we address first?
• Which of my current medications could be affecting my kidneys, and should any be stopped?
• What blood pressure target should I be aiming for to protect my kidneys?
• Are there foods I should reduce — protein, salt, potassium, phosphorus?
• How often should I retest, and what result would trigger a specialist referral?

How to Protect Your Kidney Function Between Appointments

The most controllable risk factor for kidney decline is blood pressure. Even a persistent BP of 130/80 mmHg — above the current target of 120/80 mmHg for CKD patients — accelerates glomerular damage over years. Your GP will set a specific target for you, and monitoring at home is one of the most effective ways to track whether treatment is working.

A home blood pressure monitor that stores dated readings — such as the Greater Goods Upper Arm BP Monitor — lets you arrive at your next appointment with 60 real-world readings rather than one in-clinic measurement, which can be artificially elevated by white-coat anxiety. (Affiliate link — we may earn a small commission at no extra cost to you.) In Singapore and Malaysia, home BP monitors are also widely available at Watsons pharmacies.

Beyond blood pressure, the evidence-based steps to protect kidney function include: staying well hydrated with water, limiting NSAID painkillers, avoiding dehydration during illness, keeping blood sugar tightly controlled if you have diabetes, and ensuring any imaging contrast is flagged to your radiologist so they can take precautions.

eGFR in Your Region — What to Expect

In Singapore, eGFR is reported on the standard blood panel (full renal panel) available through polyclinics and restructured hospitals. The MOH Singapore follows KDIGO (Kidney Disease: Improving Global Outcomes) guidelines for CKD staging and management.

In Australia, eGFR is automatically calculated and reported when a creatinine test is ordered through Medicare. The Kidney Health Australia patient organisation provides plain-English resources for Australians managing CKD.

In the US, eGFR reporting is standard across most laboratory panels. The National Kidney Foundation (kidney.org) offers a free CKD risk quiz and a guide to interpreting your own eGFR result, which can help you frame questions before your appointment.

This guide is for preparation purposes only and does not constitute medical advice. Always consult your doctor or specialist regarding your individual health circumstances. Read our full disclaimer.