Chronic kidney disease (CKD) can be diagnosed with blood and urine tests.
In many cases, CKD is only found when a routine blood or urine test you have for another problem shows that your kidneys may not be working normally.
Who should be tested for CKD?
See your GP if you have persistent symptoms of CKD, such as:
- weight loss or poor appetite
- swollen ankles, feet or hands
- shortness of breath
- blood in your pee (urine)
- peeing more than usual, particularly at night
Your GP can look for other possible causes and arrange tests if necessary.
Because CKD often has no symptoms in the early stages, some people at a higher risk should be tested regularly.
Regular testing is recommended if you have:
- high blood pressure
- acute kidney injury – sudden damage to the kidneys that causes them to stop working properly
- cardiovascular disease – conditions that affect the heart, arteries and veins, such as coronary heart disease or heart failure
- other conditions that can affect the kidneys – such as kidney stones, an enlarged prostate or lupus
- a family history of advanced CKD or an inherited kidney disease
- protein or blood in your urine where there's no known cause
You're also more likely to develop kidney disease if you're black or of south Asian origin.
People taking long-term medicines that can affect the kidneys, such as lithium, omeprazole or non-steroidal anti-inflammatory drugs (NSAIDs), should also be tested regularly.
Talk to your GP if you think you may need regular testing for kidney disease.
Tests for CKD
The main test for kidney disease is a blood test. The test measures the levels of a waste product called creatinine in your blood.
Your doctor uses your blood test results, plus your age, size, gender and ethnic group to calculate how many millilitres of waste your kidneys should be able to filter in a minute.
This calculation is known as your estimated glomerular filtration rate (eGFR).
Healthy kidneys should be able to filter more than 90ml/min. You may have CKD if your rate is lower than this.
A urine test is also done to:
- check the levels of substances called albumin and creatinine in your urine – known as the albumin:creatinine ratio, or ACR
- check for blood or protein in your urine
Alongside your eGFR, urine tests can help give a more accurate picture of how well your kidneys are working.
Sometimes other tests are also used to assess the level of damage to your kidneys.
These may include:
- an ultrasound scan, MRI scan or CT scan – to see what the kidneys look like and check whether there are any blockages
- a kidney biopsy – a small sample of kidney tissue is removed using a needle and the cells are examined under a microscope for signs of damage
Test results and stages of CKD
Your test results can be used to determine how damaged your kidneys are, known as the stage of CKD.
This can help your doctor decide the best treatment for you and how often you should have tests to monitor your condition.
Your eGFR results is given as a stage from 1 of 5:
- stage 1 (G1) – a normal eGFR above 90ml/min, but other tests have detected signs of kidney damage
- stage 2 (G2) – a slightly reduced eGFR of 60 to 89ml/min, with other signs of kidney damage
- stage 3a (G3a) – an eGFR of 45 to 59ml/min
- stage 3b (G3b) – an eGFR of 30 to 44ml/min
- stage 4 (G4) – an eGFR of 15 to 29ml/min
- stage 5 (G5) – an eGFR below 15ml/min, meaning the kidneys have lost almost all of their function
Your ACR result is given as a stage from 1 to 3:
- A1 – an ACR of less than 3mg/mmol
- A2 – an ACR of 3 to 30mg/mmol
- A3 – an ACR of more than 30mg/mmol
For both eGFR and ACR, a higher stage indicates more severe kidney disease.