When it comes to understanding kidney health, two terms appear repeatedly in blood test results: eGFR and creatinine. These kidney function markers serve distinct but complementary roles in helping healthcare professionals and patients understand how well the kidneys are working. If you have recently had a kidney blood test or are considering one, knowing the difference between eGFR and creatinine is a genuinely useful step in staying informed about your health.
This educational guide explains both markers clearly, compares their clinical significance, and outlines when private kidney function testing in London may be worth considering.
What Are eGFR and Creatinine? A Clear Definition
eGFR (estimated Glomerular Filtration Rate) is a calculated figure that estimates how effectively the kidneys filter waste from the blood each minute. It is derived from the serum creatinine level alongside factors such as age, sex, and ethnicity. An eGFR result is expressed in millilitres per minute per 1.73m² of body surface area.
Creatinine is a natural waste product produced by normal muscle metabolism. Healthy kidneys filter creatinine out of the blood continuously. When kidney function is reduced, creatinine can accumulate in the bloodstream, which may suggest that filtration is not occurring as efficiently as expected.
Practical Insight: Neither marker alone provides a complete picture. eGFR and creatinine are most informative when considered together, alongside your symptoms, medical history, and other test results.
eGFR vs Creatinine: Key Differences at a Glance
| Feature | eGFR | Creatinine |
|---|---|---|
| What it measures | Estimated kidney filtration rate | Waste product level in blood |
| How it is calculated | Formula using creatinine + age + sex | Directly measured in blood |
| Normal range (adults) | 90–120 mL/min/1.73m² | 60–110 µmol/L (varies by sex) |
| What a low result suggests | Reduced kidney filtration capacity | Less meaningful without eGFR context |
| What a high result suggests | N/A (higher is generally better) | May indicate reduced kidney clearance |
| Affected by muscle mass? | Indirectly | Yes, significantly |
| Used to stage kidney disease? | Yes (CKD staging uses eGFR) | Supportive marker only |
| Best used for | Monitoring kidney function over time | Detecting acute changes in kidney status |
Why Creatinine Alone May Not Tell the Full Story
Creatinine levels can vary considerably between individuals — not solely because of kidney function, but due to differences in muscle mass, diet (particularly high meat consumption), hydration, and certain medications. For example, an older adult with low muscle mass may have a seemingly "normal" creatinine level even when kidney function is meaningfully reduced.
This is why eGFR was developed: to provide a more standardised and comparable estimate of kidney health that accounts for individual characteristics. It is now the preferred marker for assessing and staging chronic kidney disease (CKD) in UK clinical guidelines.
Practical Insight: A single creatinine reading can sometimes be misleading. When both eGFR and creatinine are reported together on a kidney function blood test, the results offer a more complete and meaningful picture.
Understanding Your Kidney Function Results
eGFR Result Categories
- 90 or above — Generally considered within the normal range; kidneys are likely functioning well
- 60–89 — May suggest mildly reduced function; worth monitoring
- 45–59 — Can indicate moderately reduced function
- 30–44 — May suggest a more significant reduction in filtration
- 15–29 — Severely reduced function; appropriate healthcare input is advisable
- Below 15 — May indicate kidney failure; urgent medical care should be sought
Creatinine Reference Ranges (UK Adults)
- Men: approximately 60–110 µmol/L
- Women: approximately 45–90 µmol/L
These reference ranges can vary slightly depending on the laboratory. Results should always be interpreted alongside your eGFR and clinical context.
Practical Insight: A result outside the reference range does not automatically indicate a serious condition. Temporary factors such as dehydration, strenuous exercise, or a recent high-protein meal can influence creatinine levels. Repeat testing may sometimes be recommended to establish a reliable baseline.
Who Should Consider Kidney Function Testing?
Routine kidney screening is not always offered proactively, yet certain groups may benefit from understanding their kidney function markers on a regular basis. You may wish to consider a private kidney function test in London if you:
- Have a personal or family history of kidney disease
- Have been diagnosed with type 2 diabetes or are monitoring blood sugar levels
- Live with high blood pressure (hypertension)
- Are taking long-term medications known to affect the kidneys (e.g., NSAIDs, certain antibiotics)
- Experience recurring urinary tract infections
- Are undergoing regular health monitoring as part of a proactive wellness routine
- Are over 60 and have not had a recent kidney health check
- Have noticed unexplained fatigue, ankle swelling, or changes in urination
If any of your symptoms are severe or rapidly worsening, please seek urgent medical care immediately.
How Often Should You Have Kidney Function Markers Checked?
Frequency depends on individual circumstances. As a general educational reference:
- Low-risk adults with no known kidney concerns: Every 1–3 years as part of a broader health screening profile
- Those with diabetes or high blood pressure: Typically annually, or as recommended by an appropriate healthcare professional
- Those with known reduced kidney function: More frequently — often every 3–6 months
- Those on medications affecting kidney function: At intervals recommended by their prescribing clinician
Practical Insight: Private blood testing allows you to monitor kidney function markers at a time that suits you, without waiting for a routine NHS appointment. Many Londoners use private clinics for proactive health awareness, particularly when they have risk factors but no current symptoms.
eGFR, Creatinine, and Other Kidney Markers: What Else Might Be Included?
A comprehensive kidney function panel often includes additional markers that provide further context:
- Urea — another waste product that rises when kidney filtration is compromised
- Uric acid — may be elevated in certain kidney conditions
- Electrolytes (sodium, potassium) — the kidneys play a central role in maintaining electrolyte balance
- Urine albumin-to-creatinine ratio (ACR) — can help detect early kidney damage, particularly in people with diabetes
If you are considering a broader health check, our health screening blood test profiles can help you understand which markers may be most relevant to your circumstances.
Private Kidney Testing in London: What to Expect
At our nurse-led walk-in clinic in London, we provide straightforward blood testing and clear written results. Our clinical team can collect the sample, process it through an accredited laboratory, and provide you with your eGFR and creatinine results, along with a reference-range report.
We do not offer prescriptions, diagnosis, or treatment — our role is to provide high-quality, accessible testing and reporting to support your health awareness. If your results highlight areas of concern, our team can advise you to seek appropriate healthcare support.
Conveniently located in central London, our clinic offers same-day and walk-in blood testing appointments, and we aim to minimise waiting times where possible. For those managing ongoing health conditions or simply taking a proactive interest in wellbeing, this kind of accessible private testing can be a practical and reassuring option.
For related screening areas, you may also wish to explore our diabetes screening services, particularly if kidney health is being considered alongside blood glucose monitoring.
Frequently Asked Questions: eGFR vs Creatinine
1. What is the difference between eGFR and creatinine?
Creatinine is a waste product measured directly in the blood, while eGFR is a calculated estimate of how efficiently the kidneys filter that waste. eGFR uses creatinine alongside age, sex, and other factors to give a more standardised view of kidney function. Together, they provide a more complete picture than either marker alone.
2. Can a high creatinine level mean my kidneys are not working properly?
Elevated creatinine may suggest that the kidneys are not clearing waste as efficiently as expected, which can sometimes indicate reduced kidney function. However, creatinine can also be temporarily raised by dehydration, intense exercise, or a high-protein meal. It is always best to review results alongside your eGFR and speak to a healthcare professional for context.
3. What is a normal eGFR level in adults?
In most adults, an eGFR of 90 mL/min/1.73m² or above is generally considered within the normal range. Results between 60–89 may suggest mildly reduced function worth monitoring, while results below 60 may indicate more significant kidney function changes. These figures are reference ranges, not diagnostic thresholds.
4. Can I have a kidney function blood test privately in London?
Yes. Private kidney function testing, including eGFR and creatinine, is available at our walk-in clinic in London. No GP referral is required. You can book an appointment at a time that suits you and receive written results through our reporting process.
5. Does a low eGFR always mean kidney disease?
Not necessarily. A single low eGFR result may sometimes reflect temporary factors such as dehydration, illness, or recent strenuous activity. CKD is generally considered when eGFR is persistently reduced over three months or more. A healthcare professional would assess results in context before forming any clinical view.
6. How is eGFR calculated?
eGFR is calculated using a formula that incorporates your serum creatinine level, age, and sex. The most widely used formula in the UK is the CKD-EPI equation. Some calculations previously included ethnicity as a variable, though this is currently being reviewed across UK clinical practice.
7. Who should have eGFR and creatinine tested regularly?
People with diabetes, high blood pressure, a family history of kidney disease, or those taking medications that may affect kidney function are often advised to monitor kidney markers regularly. Those over 60 or with unexplained fatigue, swelling, or urinary changes may also wish to consider testing.
8. What happens if my eGFR result is low?
If your eGFR result comes back lower than expected, it is important to speak with an appropriate healthcare professional who can advise on next steps. This may include repeat testing to confirm the result, reviewing any medications, or further investigation. Our clinic provides results and reporting only and will signpost you appropriately.
9. Is private kidney function testing accurate?
Private kidney function testing through an accredited laboratory uses the same analytical methods as NHS testing. At our clinic, samples are processed through certified laboratories, which supports the delivery of reliable and clinically meaningful results. As with all laboratory testing, individual results should be interpreted alongside clinical context by an appropriate healthcare professional.
10. Can kidney function markers be included in a broader health check?
Yes. Kidney markers such as eGFR and creatinine are frequently included in comprehensive health screening blood panels alongside liver function, thyroid markers, full blood count, and cholesterol. This can provide a broad overview of several key areas of health in a single test.
A Note on This Content
This article has been written by a senior UK medical content writer with specialist experience in preventive health, diagnostic blood testing, and clinical health communication. The information provided is based on established UK clinical reference ranges, NHS guidance on kidney health, and published evidence from NICE and Kidney Research UK. All content is designed to inform, not to diagnose or advise on individual health conditions.
Medical Disclaimer
This article is for educational information only and is not medical advice. Symptoms or test results should be reviewed with a qualified healthcare professional. Walk In Clinic London provides testing and reporting only. If symptoms are severe, seek urgent medical care.
