Glomerular Filtration Rate (GFR) test

Radiology Department – Medical Physics

Radiology Department – Medical Physics

This image shows the bladder and kidney function
Bladder and kidney diagram

What is a GFR test?

This is a test to work out how well your kidneys are working.

Is there any preparation?

You may have a light breakfast on the morning of your test, e.g. cereal or toast. (Avoid protein e.g. sausage, bacon and eggs)

Can l take my usual medication?

You can take your normal medication. Please bring a list of your medication with you.

What if l have diabetes controlled by diet alone?

You may have a light breakfast on the morning of your test and also a light lunch during the test.

What about work? 

As the test will take most of the day you may need to take the day off.

What does the examination involve?

You will receive an injection into a vein in your arm or hand. This does not affect how you feel. The injection contains a small amount of radioactivity which goes to your kidneys. We then take blood samples from you two, three and four hours after this injection. Between the injection and the first blood sample at two hours you may leave the hospital if you wish.

When you come for your two hour blood sample we will insert a cannula into a different vein than the injection you received earlier and take the blood samples from this cannula. Once the cannula has been inserted you may leave the department between the blood samples but must stay in the hospital.”

Don’t worry if you still have unanswered questions – a member of staff will go through the procedure with you when you arrive in the department and answer any questions you might have.

How long will the test take?

The first part of the test when you have the injection will take 30 minutes and the blood samples will each take 10 minutes. You will be in the hospital for approximately five hours for the test.

What happens to the injection inside the body?

The injection will go to the kidneys and will be passed out normally in your urine.


Minor: There is a very small risk of a reaction to the injection, e.g. a rash on the skin in patients who tend to be hypersensitive.

Alternative procedure

Your consultant has asked us to do this test as it is the best way to look at the working of your kidneys. If you do not wish to have this test you must discuss this with the doctor or nurse specialist that has sent you for the test. There may be a different test that can be done.

Can l drive?     

Yes, it should have no impact on your ability to drive.

When do l get the results?

The Medical Physics staff will not be able to give you your results after the test. This information is reported to your consultant and they will arrange either a letter to inform you of the examination results, a follow up clinic appointment or you could possibly be seen by a Nurse Specialist.

Contact numbers for advice

Medical Physics Department

Tel: (0191) 445 2710

Monday to Friday 8.30am to 4.30pm