A blood test is a great way of identifying things that are wrong with the body; such as how well your kidneys are working.

You may be advised to have a blood test for your kidney function if your doctor or GP believes that there is a possible problem with your kidney. In other cases, a problem with kidney function may be picked up incidentally by a blood test for another reason.

A kidney function blood test is often used for people who are going through treatments, such as chemotherapy, to help to assess the continual good functioning of the kidneys despite the treatment.

A blood test will only take a few minutes, and can usually be done at your local hospital or GP surgery. It is likely that the blood will be taken from the inside of your elbow joint or the top of your hand. A tight band will be placed around the arm, to stop the blood flow and causing the vein to swell (this makes it easier to get the blood). The needle is then inserted into the vein and the sample taken. Once this has been completed the blood will be sent to the lab to be tested.

In the lab your blood will usually be tested for the level of urea, creatinine and dissolved salts; but what are these?


Urea is the waste product that is made when protein is broken down. If the kidneys are functioning well this should be at a low level, so a high level may indicate that the kidney is not working properly or you’re severely dehydrated.


Creatine is the waste product that is created by the muscles. Again, if there is a high level in your blood it may indicate that your kidneys are not functioning well. When testing for creatine your doctor may look at your BMI, as people with more muscle may naturally have a higher level in their blood. Compared to testing urea level, this can give a more accurate indication of the level of kidney function.

Dissolved salts

Dissolved salts refer to a list of things, including sodium, potassium, chloride and bicarbonate (you may also hear these being referred to as electrolytes). If the salt levels in your blood are high it can indicate that there is an absorption problem.

Once your results are back your doctor will go over the results and discuss what the next step is. This could be something simple like lifestyle changes or mean a carefully planned treatment pathway. Do not hesitate to contact us if your GP has recommended you have a kidney function blood test, or your results require treatment.

This article is intended to inform and give insight but not treat, diagnose or replace the advice of a doctor. Always seek medical advice with any questions regarding a medical condition.