Medically Reviewed by Dr. Andrew Stein MD, Consultant Nephrologist (kidney specialist). Last updated: April 2026
Chronic Kidney Disease (CKD) is rarely diagnosed by a single result. Because it is a “silent” condition, doctors use a systematic evaluation over a minimum of three months to differentiate it from temporary kidney stress or Acute Kidney Injury (AKI).
To reach a definitive diagnosis, medical professionals rely on the “Big Three” tests: eGFR (Blood), ACR (Urine), and Ultrasound (Imaging).
A diagnosis of CKD is confirmed when one or both of the following are present for >3 months:
Reduced Function: An estimated Glomerular Filtration Rate (eGFR) <60 mL/min (Normal range is 90–120 mL/min).
Markers of Damage: Evidence of physical kidney damage, even if the filtration rate is normal. This includes:
Protein or blood in the urine (Albuminuria or Haematuria).
Structural abnormalities found on a scan (e.g. polycystic kidneys).
Proven abnormalities on a kidney biopsy.
The eGFR is the “gold standard” for measuring how well your kidneys filter toxins. It is calculated based on your blood creatinine levels.
Modern medicine uses the CKD-EPI equation to estimate filtration. It is important to note that creatinine levels are influenced by age, sex, and muscle mass.
Important Note on Ethnicity: Historically, diagnostic equations included a “race multiplier” for Black patients, assuming higher muscle mass led to higher creatinine. However, recent medical consensus (including the NKF-ASN Task Force) has removed race from these equations to ensure earlier diagnosis and more equitable care.
Statistic: Studies showed that using the old “Black race coefficient” could overestimate kidney function by up to 16%, potentially delaying Black patients from being placed on transplant waiting lists.
While a blood test tells us how the kidneys are working, a urine test tells us if they are leaking. This is measured via the Urine Albumin-to-Creatinine Ratio (ACR).
| Category | ACR Level (mg/g) | Meaning |
| A1 | $< 30$ | Normal or mildly increased |
| A2 | $30–300$ | Moderately increased (“Microalbuminuria”) |
| A3 | $> 300$ | Severely increased (“Macroalbuminuria”) |
Statistic: Patients in the A3 category have a significantly higher risk of cardiovascular events and are at a much higher risk of progressing to kidney failure than those with an A1 rating, regardless of their eGFR.
A renal ultrasound is a key diagnostic tool used to establish the “chronicity” of the disease.
Kidney Size: Healthy kidneys are usually 10–12 cm in length. In CKD, kidneys often shrink (less than 9 cm) and become “echogenic” (scarred/bright on the scan).
Obstruction: Scans can rule out kidney stones or an enlarged prostate as the cause of the decline.
While the “Big Three” are central, your doctor will also look for secondary markers that support a CKD diagnosis:
Anaemia: Low red blood cell counts (kidneys produce the hormone EPO, which makes red cells).
Electrolyte Imbalance: High potassium (Hyperkalemia) or high phosphate levels.
Kidney Biopsy: This is rarely required. It is reserved for cases where the cause is unknown, the decline is rapid, or there is “Nephrotic Syndrome” (extremely high protein leakage).
To ensure an accurate diagnosis, doctors must avoid these five common errors:
Confusing AKI with CKD: Diagnosing CKD based on one blood test rather than waiting the required 3 months.
Creatinine Reliance: Failing to realize that a “normal” creatinine level in an elderly or frail person can still hide a dangerously low eGFR.
Ignoring the ACR: Missing kidney damage because the eGFR blood test looks normal.
Age Bias: Dismissing declining function in older adults as “just old age” when they might benefit from protective medications like SGLT2 inhibitors.
Symptoms Search: Failing to investigate why the kidneys are failing (e.g., undiagnosed diabetes or autoimmune issues).
[ ] Blood Test: eGFR confirmed $< 60$ over two tests, 3 months apart.
[ ] Urine Test: ACR checked for protein leakage.
[ ] Imaging: Ultrasound performed to check for scarring or size.
This article was medically reviewed by Dr. Andrew Stein, Consultant Nephrologist, UHCW Coventry.
Expert Guide Follow-up: Are you currently reviewing your own test results, and do you know if your eGFR was calculated using the updated race-neutral CKD-EPI equation?
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