Kidney blood tests are part of many routine check-ups, but the numbers can be confusing. eGFR is the key figure, and one low result does not always mean kidney disease.
Imagine your annual check shows an eGFR of 58 and the letter mentions “stage 3a”. You have never had a kidney problem. Is this serious?
What creatinine and eGFR are
- Creatinine: a waste product from muscle, removed by the kidneys
- eGFR: an estimate of how well the kidneys filter blood, calculated from creatinine, age and sex
Stages of chronic kidney disease (CKD)
- G1: 90 or more (normal, but with other signs of kidney damage)
- G2: 60 to 89
- G3a: 45 to 59
- G3b: 30 to 44
- G4: 15 to 29
- G5: below 15 (kidney failure)
Important points
- CKD is diagnosed only if results stay low for at least 3 months, or there are other signs of kidney damage
- A urine test for protein (ACR) is also important
- Dehydration, a meat-heavy meal or some medicines can temporarily change results
Acute kidney injury
A sudden rise in creatinine over hours or days can mean acute kidney injury, which needs prompt assessment, especially in people who are unwell.
Protecting your kidneys
- Control blood pressure and blood sugar
- Avoid regular use of anti-inflammatory painkillers unless advised
- Stay hydrated, especially when unwell
- Do not smoke
Lab ranges vary
Reference ranges differ between laboratories and countries, and some use different units. Always compare your result with the range printed on your report and discuss it with your healthcare provider.
Why eGFR matters even when you feel well
Your kidneys filter about 180 litres of blood every day, removing waste and extra fluid, balancing salts and helping control blood pressure. They also help make red blood cells and keep bones healthy.
Kidney function can fall by more than half before most people notice any symptoms. By the time symptoms such as tiredness, swelling or itching appear, kidney disease may already be advanced. That is why people with diabetes, high blood pressure, heart disease or a family history of kidney failure are usually offered regular blood and urine tests.
The urine ACR test
The urine albumin-to-creatinine ratio (ACR) checks for protein leaking into the urine. Protein in the urine is an early sign of kidney damage and is linked to a higher risk of heart disease.
CKD is described using both eGFR (G stages) and ACR (A stages). For example, “G3a A2” means moderately reduced kidney function with moderately raised protein in the urine. Both numbers help your healthcare provider decide how often to monitor you and which treatments to offer.
What can make results look worse than they are
- Dehydration, vomiting or diarrhoea
- Eating a large amount of cooked meat in the hours before the test
- Intense exercise
- High muscle mass, which raises creatinine
- Some medicines, such as trimethoprim, which raise creatinine without harming the kidneys
- Creatine supplements
Medicines that can affect the kidneys
Some medicines can harm the kidneys or need dose changes when kidney function is reduced. These include anti-inflammatory painkillers such as ibuprofen, some blood pressure medicines when you are dehydrated, certain antibiotics and lithium. Always tell your healthcare provider and pharmacist about all the medicines and supplements you take, and ask whether any need adjusting.
“Sick day rules”
If you have CKD, diabetes or heart failure, you may be advised to pause certain medicines temporarily when you are unwell with vomiting, diarrhoea or fever and cannot drink normally. These can include some blood pressure tablets, diuretics, metformin and SGLT2 inhibitors. Only do this if your healthcare team has given you a sick day plan, and restart once you are eating and drinking normally.
Treatments that slow kidney disease
- Good blood pressure control, often with ACE inhibitors or ARBs
- SGLT2 inhibitors, which protect the kidneys in many people with CKD
- Managing diabetes and cholesterol
- Stopping smoking and keeping active
- Regular monitoring so changes are caught early
When kidney function is very low
If eGFR falls below about 15, a kidney specialist team will discuss options with you, including dialysis, a kidney transplant or conservative care focused on symptoms and quality of life. Planning early gives you time to understand each option and make choices that fit your life.
Symptoms of more advanced kidney disease
Most people with early CKD have no symptoms at all. As kidney function falls further, people may notice tiredness, swollen ankles or puffiness around the eyes, needing to pass urine more at night, itchy skin, poor appetite, nausea, muscle cramps and difficulty concentrating.
These symptoms are not specific to kidney disease, which is another reason blood and urine tests are so important for anyone at risk.
Kidney disease and heart health
CKD and heart disease are closely linked. People with CKD are more likely to have a heart attack or stroke than to need dialysis. Controlling blood pressure, cholesterol and blood sugar, and not smoking, protect both the kidneys and the heart. Your healthcare provider may recommend a statin even if your cholesterol does not seem high.
eGFR, ethnicity and fairness
Older eGFR equations included an adjustment for Black ethnicity. Many countries and laboratories have now moved to equations that do not use race, to avoid delays in diagnosis and referral. Ask your healthcare provider which equation your laboratory uses if you are unsure how your result was calculated.
Questions to ask at your next appointment
- What is my eGFR, and how has it changed over time?
- What is my urine ACR?
- Do any of my medicines need adjusting for my kidney function?
- How often should my kidneys be checked?
- Should I have a sick day plan?
Kidney health around the world
Chronic kidney disease affects an estimated one in ten adults worldwide, and many do not know they have it. Access to dialysis and transplantation varies hugely between countries, which makes early detection and prevention especially important. Simple, low-cost steps such as checking blood pressure, testing urine for protein and avoiding unnecessary anti-inflammatory painkillers can make a real difference.
Frequently asked questions
Is an eGFR of 60 bad?
Not necessarily. It can be normal for age if there are no other signs of damage. Your clinician will decide.
Can eGFR improve?
Sometimes, especially if a temporary cause is fixed.
What is a normal eGFR for my age?
eGFR naturally falls slowly with age. Many healthy older adults have an eGFR between 60 and 90.
Does drinking more water improve eGFR?
If you are dehydrated, rehydrating can improve results. Drinking excessive amounts does not improve healthy kidney function.
Can kidney disease be reversed?
Damage is usually permanent, but progression can often be slowed or stopped, especially when found early.
But I feel fine. Does it matter?
Early kidney disease usually causes no symptoms, which is why blood tests matter.
Your next step: Ask for your eGFR and urine ACR results at your next check-up, and keep a record.
Related: Early signs of kidney disease · Normal lab values cheat sheet
Sources: KDIGO clinical practice guideline for CKD, National Institute for Health and Care Excellence (NG203), National Kidney Foundation, Kidney Care UK.
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