It is a common misconception that Chronic Kidney Disease (CKD) is a single diagnosis.
In reality, it is a clinical syndrome—a collection of signs and symptoms caused by various underlying conditions.
Because you can technically have “CKD” while your kidneys are still functioning at 100%, defining it requires a bit of nuance. Here is a clearer breakdown of what CKD actually means and how it is classified.
At its simplest, Chronic Kidney Disease is defined by the presence of kidney damage or a reduction in kidney function that persists for more than three months.
It is important to remember that CKD is not a diagnosis in itself; it is a signal that an underlying cause (such as diabetes, high blood pressure, or inflammation) is affecting the kidneys.
The Two Pillars of CKD
To be diagnosed with CKD, a patient must meet one of the following two criteria for at least 90 days:
Functional CKD: A gradual loss of kidney function over time, typically measured by a filtration rate (GFR) falling below a certain threshold.
Structural CKD: Evidence of physical damage to the kidneys, even if the kidneys are still filtering blood at a normal rate.
According to the latest international standards, the clinical definition is split into two categories. If either of these persists for over three months, a CKD classification is made:
1. Functional Impairment
Low GFR: An estimated Glomerular Filtration Rate (eGFR) of less than 60 mL/min/1.73m².
Essentially, if your “kidney percentage” is consistently below 60%, it is classified as CKD regardless of whether there is physical damage.
2. Structural/Marker Evidence
Even if your eGFR is above 60 (normal function), you have CKD if there is evidence of kidney damage shown by:
Albuminuria: Persistent protein leaking into the urine.
Haematuria: Blood in the urine (after ruling out other causes like stones or cancer).
Structural Issues: Abnormalities found on an ultrasound (e.g. Polycystic Kidney Disease).
Pathological Evidence: Abnormalities found via a kidney biopsy.
History: Anyone who has received a kidney transplant is classified as having CKD.
Prevalence: CKD affects roughly 10% of adults in the UK.
Severity: Most cases (Stages 1–3B) are mild and often related to natural aging. In many older patients, it is viewed more as a “risk factor” than a progressive disease.
Risks: While CKD increases the risk of heart disease and high blood pressure, actual kidney failure is rare. Only about 1% of people with CKD eventually require dialysis or a transplant (ESRF).
Action: Early detection is vital. Identifying the cause early can slow progression and significantly reduce complications.
CKD is graded from Stage 1 to Stage 5 based on the eGFR (filtration rate). This helps doctors determine the level of monitoring and treatment required:
| Stage | Severity | GFR Range |
| Stage 1 | Normal function, but evidence of damage | 90+ |
| Stage 2 | Mildly decreased function | 60–89 |
| Stage 3A/B | Mild to moderate decrease | 30–59 |
| Stage 4 | Severely decreased function | 15–29 |
| Stage 5 | Kidney failure (End-stage) | < 15 |
Note: Tracking your data is the best way to stay informed. Use tools like PKB (Patients Know Best) to monitor your blood results and GFR trends over time.
Do you have your most recent eGFR or urine ACR (protein) results, or are you just looking into the general definitions for now?
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