Chronic kidney disease: what a low eGFR and a urine test really mean

Chronic kidney disease (CKD) is kidney damage or reduced filtering that lasts at least 3 months. In lab terms, one of two things has to hold for 3 or more months: an eGFR under 60 (the estimated filtration rate, how fast your kidneys clean your blood, in mL/min/1.73m2), or protein leaking into your urine (an albumin-to-creatinine ratio, or ACR, of 30 mg/g or higher). Because a single reading can be thrown off by dehydration, a short illness, or a big protein meal, one low eGFR is repeated and paired with a urine test before anyone calls it CKD.

What is chronic kidney disease?

Chronic kidney disease is defined as abnormalities of kidney structure or function, present for more than 3 months, with implications for health.KDIGO 2024 Clinical Practice Guideline for CKD

Two phrases in that definition carry the weight. "More than 3 months" rules out a temporary dip. "Structure or function" means damage counts even when filtration still looks fine, which is why a urine protein test sits alongside the eGFR blood test. Your kidneys filter waste and extra fluid from your blood; how that filtering works is the background this result sits against. ¹

The two numbers it is graded on

CKD is measured on two axes at once. The first is the eGFR, an estimate of filtration from a blood test. The second is the urine ACR, the amount of a protein called albumin leaking into the urine. Each catches damage the other can miss, so a normal eGFR alone does not rule CKD out.

Once both numbers are known, they place you on a grid. Here is where an example eGFR would land against the filtration (G) stages.

The combined risk grid (CGA)

Reading across a row shows the point of the two axes: at the same eGFR, more protein in the urine means higher risk. That is why a normal eGFR with heavy albumin still counts as CKD. ¹

If you have a recent creatinine result, the tool below turns it into an estimated filtration rate and shows which G stage it lands in.

What causes chronic kidney disease?

Two conditions cause most of it. Diabetes damages the kidney's tiny filters through years of high blood sugar, and high blood pressure wears them down through years of extra force. Together they are the leading causes of kidney failure in the US, behind about 3 of every 4 new cases. ³

• Glomerular diseases, damage to the kidney's filtering units, often from autoimmune conditions like lupus
• Polycystic kidney disease, an inherited condition where cysts crowd out healthy tissue (worth family screening)
• Repeated urinary infections or a long-term blockage, such as an enlarged prostate or kidney stones
• Long-term use of some medicines, including regular high-dose NSAID painkillers

What are the symptoms of kidney disease?

Usually none, until it is advanced. Early CKD produces no symptoms, which is why it is found on blood and urine tests rather than by how you feel. More than 1 in 7 US adults, about 35.5 million people, have CKD, and as many as 9 in 10 of them do not know it. ³

When symptoms do appear later, they can include swelling in the ankles or legs, foamy urine, tiredness, poor appetite, trouble sleeping, itchy skin, needing to urinate more at night, and breathlessness. By that point the disease is often advanced, which is the argument for testing early.

How is CKD diagnosed and monitored?

eGFR is usually estimated from serum creatinine, a muscle byproduct your kidneys clear. Because creatinine tracks muscle mass, KDIGO 2024 advises confirming a borderline result with a cystatin C-based eGFR when a decision depends on the exact number. The 2021 equations doctors use to calculate eGFR also removed race as a variable. ¹²

1. 1Confirm it persistsA low eGFR or raised urine ACR is repeated after about 3 months. One abnormal day is not CKD.
2. 2Test both axesDiagnosis needs an eGFR blood test and a urine albumin-to-creatinine ratio, because each catches damage the other can miss.
3. 3Confirm the number when it matterseGFR from creatinine can be thrown off by muscle mass. When a decision hinges on the exact value, a cystatin C-based eGFR is used to confirm it.
4. 4Stage and set a recheck cadenceOnce confirmed, the G and A stages set how often to recheck, from yearly for low risk to every few months for higher risk.

Screening makes sense for anyone with diabetes, high blood pressure, heart disease, obesity, a family history of kidney failure, or age over 60. Because polycystic kidney disease runs in families, close relatives of someone with it may be screened too.

What slows chronic kidney disease down?

The biggest levers are the same ones that cause it. KDIGO 2024 and the trial evidence agree: control blood pressure and blood sugar, protect the filters, and stop harming them. ¹

• Keeping blood pressure in the range your clinician sets, the strongest lever alongside blood sugar
• Keeping blood sugar controlled if you have diabetes
• Kidney-protective medicines from a few classes that lower urine protein and ease pressure on the filters, chosen and monitored by a clinician
• Not smoking, and staying active at a level that suits you
• Reviewing your medicines and supplements with a clinician or pharmacist so nothing is quietly harming reduced kidneys

Progression can be slowed, and often halted. Caught at G1 to G3, most people with CKD never reach kidney failure, especially when blood pressure and blood sugar are controlled early. That is the case for finding it on a test before it can be felt: the earlier the two numbers are known, the more can be done with them. ⁵