Chronic kidney disease (CKD) is one of the most common long-term conditions in the UK, affecting around 3 million people — the vast majority of whom are entirely unaware of it. Unlike many conditions, kidney disease is often described as clinically silent in its early stages: it can progress considerably before producing any noticeable symptoms. This makes the answer to the question will a blood test show kidney disease not just medically interesting, but genuinely important. The answer is yes — and a blood test is, in fact, the primary way kidney disease is identified in the UK, often before it has caused any meaningful symptoms at all.
Understanding which blood markers matter, what they measure, and how to interpret them is the most useful thing you can do to take your kidney health seriously.
Why Kidney Disease Is So Often Missed Without Testing
According to the UK Kidney Association, CKD is often described as silent — meaning it does not produce a clear, distinctive symptom complex in the way many other conditions do. Symptoms such as fatigue, breathlessness, and fluid retention do appear as the disease progresses, but by the time they become noticeable, a significant degree of kidney function has typically already been lost. This is why blood testing — rather than waiting for symptoms — is the most reliable early detection strategy available.
The kidneys have remarkable reserve capacity: they can lose a substantial proportion of their function before the body signals that something is wrong. A person can have an eGFR (estimated glomerular filtration rate) of 50 — meaning their kidneys are working at roughly half normal capacity — and feel completely well. This is not reassuring; it is the reason why opportunistic blood testing matters so much, particularly in people with known risk factors for kidney disease.
The Primary Blood Test for Kidney Disease: eGFR and Creatinine
According to NHS guidance, the main test for kidney disease is a blood test. Specifically, it measures the level of creatinine — a waste product produced by normal muscle activity — in the bloodstream. Healthy kidneys continuously filter creatinine out of the blood and excrete it in urine. When the kidneys’ filtering capacity declines, creatinine builds up in the blood — and this rise in serum creatinine is the core signal that something is wrong.
A single creatinine result is informative but limited on its own, because creatinine levels vary naturally with muscle mass, age, sex, and diet. To make the result more clinically meaningful, UK laboratories automatically calculate the estimated glomerular filtration rate (eGFR) alongside every creatinine measurement, using the CKD-EPI (2009) formula approved by NICE. The eGFR represents an estimate of how many millilitres of blood the kidneys are filtering per minute per 1.73 square metres of body surface area.
According to Kidney Research UK, an eGFR of 90ml/min or above is within the normal range. A value below 60ml/min, if sustained across two separate tests at least 90 days apart, indicates chronic kidney disease. An eGFR of 15 or below may indicate kidney failure, requiring immediate medical assessment. It is important not to over-interpret a single mildly reduced eGFR — the UK Kidney Association notes that borderline values just below 60 should prompt repeat testing rather than immediate alarm, and that an eGFR of 60 to 89 is considered normal in the absence of any other markers of kidney damage.
Factors That Can Affect eGFR Accuracy
The eGFR formula incorporates creatinine alongside age and sex — but it has recognised limitations. People with very high muscle mass (such as bodybuilders) may have naturally elevated creatinine and therefore a falsely low eGFR. Conversely, those with very low muscle mass — the elderly or those with muscle-wasting conditions — may have a falsely reassuring eGFR despite meaningful kidney impairment. Where clinical uncertainty exists, cystatin C — an alternative kidney marker produced at a constant rate regardless of muscle mass — can be used to supplement or confirm the eGFR result, though it is not yet widely available in all UK settings. Patients are also advised to avoid eating red meat in the 12 hours before an eGFR blood test, as cooked meat temporarily raises creatinine levels and can affect the result.
The Second Key Marker: Albumin-to-Creatinine Ratio (ACR)
Blood creatinine and eGFR assess the kidneys’ filtering capacity — but they do not capture another critical aspect of kidney health: whether the kidneys are retaining protein as they should. Healthy kidneys act as a selective filter, keeping large molecules like albumin (a protein) in the bloodstream while excreting waste. When the kidneys are damaged, albumin leaks into the urine — a condition called albuminuria or proteinuria — which can appear many years before eGFR begins to decline.
The albumin-to-creatinine ratio (ACR) is measured from a urine sample rather than a blood test, but it is an essential companion to the eGFR in assessing kidney health. The UK Kidney Association states that urinary albumin leak may be the very first sign of kidney disease for many patients — particularly those with diabetes — and can precede a detectable fall in eGFR by years. According to Kidney Care UK, an ACR below 3mg/mmol requires no further action, a result of 3 to 70mg/mmol warrants a repeat test within three months, and above 70mg/mmol indicates significant proteinuria requiring prompt clinical assessment.
Together, the eGFR and ACR form the basis of the UK and international CKD staging system — the KDIGO G and A classification — which places patients on a grid from G1A1 (mildest) to G5A3 (most severe), guiding clinical decisions about monitoring frequency, treatment, and specialist referral.
Other Blood Markers That Support Kidney Disease Assessment
Beyond creatinine and eGFR, a comprehensive kidney health blood panel can reveal several additional features that are relevant to kidney disease diagnosis and management:
Urea
Urea is another waste product filtered by the kidneys. Elevated blood urea, alongside raised creatinine, strengthens the picture of impaired kidney function. It is worth noting that urea can also be elevated by dehydration or a high-protein diet, so it is interpreted in context rather than in isolation.
Electrolytes — Sodium, Potassium, Bicarbonate
The kidneys regulate the balance of electrolytes in the blood. As kidney function declines, sodium and potassium levels can become dysregulated, and bicarbonate may fall — producing metabolic acidosis. Abnormalities in these markers, particularly hyperkalaemia (raised potassium), can have serious cardiac consequences and are closely monitored in CKD management.
Full Blood Count
Anaemia is a common consequence of CKD. The kidneys produce erythropoietin, a hormone that stimulates red blood cell production. When kidney function falls, erythropoietin production declines, leading to a normochromic, normocytic anaemia that contributes significantly to the fatigue and breathlessness of advanced CKD.
Phosphate and Calcium
The kidneys play a central role in calcium-phosphate balance and vitamin D activation. In CKD, phosphate tends to rise while calcium and active vitamin D fall — disrupting bone metabolism and cardiovascular health. These markers are closely monitored from Stage 3 CKD onwards.
Parathyroid Hormone (PTH)
Secondary hyperparathyroidism — where the parathyroid glands overproduce PTH in response to low calcium and high phosphate — is a common complication of CKD that contributes to bone disease. PTH is measured as part of the metabolic monitoring of patients with established CKD.
A patient seen at our Birmingham clinic — a woman in her late fifties with well-controlled type 2 diabetes — attended for a routine health review. She had no kidney symptoms. A comprehensive private blood test identified a mildly elevated creatinine and an eGFR of 58ml/min. Repeat testing three months later confirmed a sustained eGFR below 60 alongside a mildly raised ACR — consistent with Stage 3A CKD. Early identification allowed her to start appropriate management promptly, including medication review and lifestyle modifications, significantly reducing her risk of further progression.
Who Should Be Tested for Kidney Disease?
Given that CKD is so often asymptomatic in its early stages, proactive testing is especially important for those with elevated risk. The NHS and NICE recommend regular kidney function monitoring for people with:
- Type 1 or type 2 diabetes
- High blood pressure (hypertension)
- Cardiovascular disease — heart failure, previous heart attack, or stroke
- A family history of kidney disease or inherited kidney conditions such as polycystic kidney disease
- Recurrent kidney infections or a history of kidney stones
- Obesity — a recognised independent risk factor for CKD progression
- Regular long-term use of non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen
- Systemic autoimmune conditions such as lupus or vasculitis
For anyone in these categories, annual kidney function testing — at a minimum — is clinically prudent. If you have not had a kidney function test recently, or if you are outside NHS-registered GP care and would like a comprehensive assessment, a private blood test provides a straightforward and efficient way to understand your baseline kidney health.
Symptoms That Should Prompt Urgent Testing
While early kidney disease is often silent, more advanced kidney impairment can produce a range of symptoms that should always prompt prompt GP assessment:
- Persistent fatigue or breathlessness not explained by another condition
- Ankle, foot, or leg swelling
- Changes in urination — going more or less frequently, foamy or frothy urine indicating protein, or blood in the urine
- Persistent itching without a clear skin cause
- Nausea, reduced appetite, or unintentional weight loss
- Difficulty concentrating or a persistent sense of mental fogginess
- High blood pressure that is new or increasingly difficult to control
- Muscle cramps, particularly at night
If any of these resonate alongside risk factors for kidney disease, please do not wait. A face-to-face GP consultation at The Private GP in Birmingham gives you access to a GMC-registered doctor who will assess your symptoms thoroughly, arrange same-day kidney function testing, and act promptly on any findings — without the delay of an NHS appointment. Same-day appointments are available. Book today.
What Happens After an Abnormal Kidney Blood Test?
If an eGFR below 60 or a raised ACR is found, the next step is confirmation rather than immediate alarm. According to Kidney Care UK and the South and West NHS Devon CKD guidance, a single abnormal result prompts a repeat test within two to three weeks to rule out acute kidney injury or transient changes. If the second test confirms the findings, a formal CKD diagnosis is made and an appropriate management plan is established.
Further investigations may include a urine dipstick for haematuria (blood in the urine), an ultrasound to assess kidney structure, and review of any medications that may be affecting kidney function — particularly NSAIDs, certain antibiotics, and ACE inhibitors or ARBs in specific contexts. Depending on the CKD stage and ACR category, specialist nephrology referral may be arranged. The UK Kidney Association guidance notes that deteriorating renal function requires rapid assessment, and that referral to or discussion with a specialist is usual from Stage 3B (eGFR 30–44ml/min) onwards.
How a Private Blood Test Can Help
At The Private GP in Birmingham, our private blood testing service includes a comprehensive renal profile covering creatinine, eGFR, urea, electrolytes, full blood count, and more — with same-day results and clinical interpretation by a GMC-registered GP. If an eGFR blood test is what you specifically need, we can arrange this quickly and efficiently, with results explained clearly in the context of your health history and risk factors.
Whether you have risk factors for kidney disease, have received a borderline result you want to understand better, or simply want a clear picture of your kidney health, we are here to provide the answers you need — promptly, professionally, and without unnecessary waiting. Early identification of kidney disease is one of the most meaningful steps you can take to protect your long-term health.
Frequently Asked Questions
- What does an eGFR blood test show?
The eGFR (estimated glomerular filtration rate) is calculated from your blood creatinine level alongside your age and sex, using the NICE-approved CKD-EPI formula. It estimates how many millilitres of blood your kidneys are filtering per minute — a direct measure of kidney function. An eGFR above 90ml/min is normal. A value below 60ml/min, confirmed on two tests at least 90 days apart, is diagnostic of chronic kidney disease. Our private eGFR blood test in Birmingham provides same-day results with full GP interpretation.
- Can a normal blood test rule out kidney disease?
Not entirely. A normal creatinine and eGFR means kidney filtering capacity is adequate at the time of testing — but early kidney damage can be present without any change in eGFR if the kidneys are compensating. Albumin in the urine (measured via the ACR urine test) can appear years before the eGFR starts to fall, particularly in diabetes and hypertension. A full kidney assessment should include both a blood test and a urine ACR for the most complete picture.
- How quickly can kidney disease be detected with a blood test?
A blood creatinine and eGFR result is available within hours of the sample being taken. At The Private GP, results from a private blood test are typically available the same day, with a GP on hand to interpret the findings and advise on any necessary next steps. If an abnormal result requires confirmation, a repeat test is usually arranged within two to three weeks.
- What level of eGFR should I be worried about?
An eGFR below 60ml/min on two tests at least 90 days apart indicates chronic kidney disease and warrants clinical management. An eGFR of 30 to 44ml/min (Stage 3B) represents a significantly elevated risk of both kidney failure and cardiovascular disease, and specialist input is usually recommended. An eGFR at or below 15ml/min may indicate kidney failure and requires immediate medical attention. A single borderline result between 50 and 60 should not be over-interpreted — repeat testing and clinical context matter considerably.
- Should I get a kidney function test if I have diabetes or high blood pressure?
Yes — and regularly. Both diabetes and hypertension are the most common causes of CKD in the UK, and NICE recommends annual kidney function monitoring for all people with these conditions. Kidney damage from diabetes and hypertension develops gradually and silently, which means regular testing is the only reliable way to detect it early enough to slow or prevent further progression. A private full health check-up at The Private GP includes kidney function assessment alongside a comprehensive range of other health markers, with same-day results and GP review.