The NHS diagnoses Chronic Kidney Disease (CKD) primarily through a combination of blood and urine tests. Because the kidneys often do not cause pain even when they are struggling, these clinical measurements are the only reliable way to assess how well they are filtering waste. The diagnosis typically focuses on two main markers: the estimated Glomerular Filtration Rate (eGFR), which measures filtration speed, and the Albumin-to-Creatinine Ratio (ACR), which checks for protein leakage.
What We Will Cover in This Article
- The role of the eGFR blood test in determining kidney stage.
- How the Urine ACR test detects early signs of filter damage.
- The importance of blood pressure monitoring in the diagnostic process.
- Understanding the ‘Stages’ of CKD used by the NHS.
- When additional tests like ultrasounds or biopsies are required.
- How the NHS identifies individuals who need proactive screening.
- What happens after a diagnosis is confirmed.
The Primary Blood Test: Understanding eGFR
The cornerstone of an NHS kidney diagnosis is a blood test that measures the level of creatinine, a waste product produced by your muscles. Healthy kidneys filter creatinine out of the blood at a steady rate. If your creatinine levels are high, it suggests the kidneys are not filtering effectively.
Clinicians use your creatinine level, along with your age and sex, to calculate your eGFR (estimated Glomerular Filtration Rate). Think of the eGFR as a percentage of your total kidney function. A ‘normal’ eGFR is usually above 90. If your eGFR is consistently below 60 for more than three months, it is typically classified as Chronic Kidney Disease.
- Stable Readings: The NHS usually requires two or more tests over a three-month period to confirm a ‘chronic’ condition rather than a temporary dip.
- Creatinine Sensitivity: Factors like high protein diets or intense exercise can sometimes affect creatinine levels, so your doctor will consider your lifestyle.
- Calculation: The eGFR provides a more accurate picture than looking at creatinine alone.
The Urine ACR Test: Checking for ‘Leaky’ Filters
While the blood test measures speed, the urine test measures the ‘quality’ of the kidney’s filters. The NHS uses a test called the Urine Albumin-to-Creatinine Ratio (ACR). This test looks for albumin, a type of protein that should remain in your blood. If albumin is found in your urine, it means the tiny filters in your kidneys (glomeruli) are damaged and ‘leaking’.
This test is particularly important because it can detect kidney damage even when the eGFR blood test is still normal. This is often the case in people with diabetes, where the kidneys are damaged but are ‘over-filtering’ to compensate, keeping the blood test looking healthy while the urine test reveals the underlying problem.
| Test Marker | What it Detects | Clinical Significance |
| eGFR | Filtration speed | Tells the doctor what ‘stage’ of kidney disease you are in. |
| Urine ACR | Protein leakage | Identifies damage to the filter walls; predicts risk of progression. |
| Dipstick | Blood/Leukocytes | Used as a quick screen for infections or inflammation. |
How the NHS Stages Chronic Kidney Disease
Once your eGFR (a blood test) and ACR (a urine test) results are in, the NHS uses a staging system to categorise the severity of chronic kidney disease (CKD). This system combining eGFR stages G1–G5 with albuminuria stages A1–A3 helps doctors decide how often to monitor you and which treatments are most appropriate.
- Stages 1 and 2 (G1–G2): eGFR is 60 or above, but there are other signs of kidney damage, such as protein in the urine or structural changes on a scan.
- Stage 3 (G3a and G3b): eGFR between 30 and 59. This represents moderate reduction in kidney function and is a common stage at which CKD is first diagnosed.
- Stage 4 (G4): eGFR between 15 and 29. This is advanced kidney disease, when symptoms like tiredness, poor appetite and swelling often become more noticeable.
- Stage 5 (G5): eGFR below 15 or the need for dialysis. This is known as kidney failure, when the kidneys can no longer support the body without treatment.
Source: https://111.wales.nhs.uk/Kidneydisease,chronic/
Additional Diagnostic Tools
In some cases, your GP or a kidney specialist (nephrologist) may require more detailed information to find the specific cause of the kidney damage. These tests are not always necessary for every patient but are used if the cause of the decline is unclear or if your kidney function is dropping rapidly.
- Ultrasound Scan: Uses sound waves to create a picture of your kidneys to check for physical abnormalities, blockages, or kidney stones.
- Blood Pressure Monitoring: Frequent checks or a 24-hour monitor to see how your blood pressure is affecting your kidneys.
- Kidney Biopsy: A very small sample of kidney tissue is taken with a needle to be examined under a microscope. This is the ‘gold standard’ for identifying specific types of inflammation.
To Summarise
The NHS diagnoses CKD through a combination of the eGFR blood test and the Urine ACR test. These results, monitored over at least three months, allow clinicians to stage the severity of the condition and create a management plan. By checking both the filtration rate and the integrity of the kidney filters, the NHS can identify kidney issues early, providing the best opportunity to slow the progression of the disease through lifestyle and medication.
If you experience severe, sudden, or worsening symptoms, call 999 immediately.
Do I need to fast before a kidney blood test?
Usually, no fasting is required for an eGFR test, but your GP will let you know if you need to avoid certain foods (like cooked meat) the night before.
What is a ‘normal’ kidney function result?
An eGFR of 90 or above is generally considered normal, provided there is no protein in the urine or other signs of damage.
Why does the NHS wait three months to confirm CKD?
A temporary drop in kidney function can be caused by dehydration or a minor illness; the three-month window ensures the condition is truly ‘chronic’.
Is an ultrasound always needed for diagnosis?
No, most cases of CKD are diagnosed based on blood and urine tests alone, especially if you have a known cause like diabetes.
Can my pharmacist diagnose me?
Pharmacists can review your medications and provide advice, but a formal diagnosis must be made by a doctor using laboratory tests.
Will I be referred to a specialist immediately?
Most people with Stage 1, 2, or 3a CKD are managed by their GP surgery. Referrals to a nephrologist usually happen for Stage 4 or if function is dropping quickly.
Authority Snapshot
This article outlines the NHS diagnostic pathway for Chronic Kidney Disease, incorporating NICE clinical guidelines. Dr. Rebecca Fernandez, a UK-trained physician with experience in internal medicine, general surgery, and emergency care, has reviewed this content. Her background in patient assessment and interpreting complex diagnostic results ensures that this information is accurate and emphasizes the importance of a structured clinical approach to renal health.
