Getting tested is the only way to find out how well your kidneys are working, as CKD doesn’t usually cause symptoms until your kidneys are badly damaged. The tests not only help your doctor work out whether you have CKD, they also show how seriously damaged your kidneys are.
Testing for CKD: Blood test
What does it involve?
Your doctor or nurse will take a sample of your blood and send it away for lab testing. They should tell you not to eat meat for at least 12 hours before you have the test, as that can skew the results.
What does it look for?
Creatinine, a waste product from your muscles found at higher levels in your blood when your kidneys aren’t working properly. The amount that’s normal varies depending on your gender, how old you are and how much muscle you have. But an average normal level is 60-120 mcmol/L – the lower the creatinine, the better.
What do the results mean?
Your doctor will use your creatinine result to work out something called your estimated glomerular filtration rate (eGFR), a measure of how well your kidneys are filtering waste from your blood per 1.73m of your body area.
Healthy kidneys can filter more than 90ml of waste every minute. The worse the damage to your kidneys, the lower your eGFR will be – so, the higher the eGFR, the better. However, eGFR isn’t used on its own and an eGFR as low as 60 may be considered normal if there isn’t any other sign of kidney disease. If your eGFR is less than 60ml/min/1.73m(2), your doctor will normally want to repeat the test in a couple of weeks.
Did you know? Some people may make more creatinine naturally and have a low eGFR, including body builders and pregnant women.
Testing for CKD: Urine test
What does it involve?
You’ll be asked to take a sample of your wee early in the morning.
What does it look for?
Two things that suggest your kidneys may not be working well:
- The ratio of a type of protein called albumin to creatinine. This is called the albumin: creatinine ratio (ACR)
- Blood in your wee
How will my doctor use the test?
Your ACR is staged from 1-3.
- A1 is an ACR of below 3mg/mmol
- A2 means your ACR is 3 to 30mg/mmol
- A3 is an ACR of above 30mg/mmol
The higher your ACR, the more serious your kidney disease may be.
What do the results mean?
If your ACR is below 3mg/mmol, no further action is needed. If it’s 3 to 70mg/mmol, your doctor will want to repeat the test within the next three months. Above 70mg/mmol means protein in your wee is so high a repeat test isn’t necessary.
If the test shows blood in your wee, your doctor may want to repeat the test to check for a urinary tract infection (UTI).
What happens after you've been tested for CKD?
- If your results suggest kidney damage, doctors will usually carry out the tests again over the next three months. If your tests continue to show a low eGFR (and/or a high ACR), they will diagnose CKD and start your treatment.
- If your eGFR stays above 60ml/min, and/or your ACR stays below 3mg/mmol, it’s likely your doctor will rule out CKD, as long as there are no other markers of kidney damage (such as abnormalities seen on scans).
- If your results don’t suggest CKD but you have risk factors that might mean you could develop kidney disease in the future, your doctor should suggest you have these tests every year to monitor your kidney health.
- Your doctor will carry out some other tests to check your heart health, as that is strongly linked to kidney health, including looking at your blood pressure and cholesterol levels.
- If your eGFR is under 60ml/min, you’ll probably need an ultrasound scan of your kidneys. This is to check you have two kidneys (1 in 1000 people are born with one), and look for causes of CKD, like polycystic kidney disease.
AstraZeneca has contributed to the funding of this material as part of a Patient Advocacy Group Partnership between Kidney Care UK and AstraZeneca UK Limited. AstraZeneca has had no editorial input into or control over the content which has been independently owned and created by Kidney Care UK.