Know Your Kidney Numbers
People with chronic kidney disease have a lot of blood tests and urine tests. On this page we talk about some of the more important ones to help you understand your condition. You can talk to your GP about the others.
Knowing what the numbers on your blood and urine test results mean will help you learn more about your health. You can make changes to your lifestyle and the numbers can mark your progress. If you have kidney disease, some of your results may be outside the normal range but they can be considered acceptable for someone with damaged kidneys. Your doctor or nurse will guide you on what your own individual target should be.
Having the tests
Most tests don’t need any special preparation, but for those that do, it is important you follow the instructions given to you. If you are not given any instructions, you should still ask if there is anything you need to do to prepare for the test. If you are unsure, ask your doctor or practice nurse.
It is important that you have your tests done in the time frame your doctor or nurses requests. It is one way they can keep track of your health between appointments.
What are the numbers I should know?
Below are just a few of the tests you might have to check how your kidneys are working. There will be many others not mentioned here. The more common ones are discussed below.
Blood pressure is the force of the blood against the artery (blood vessel) walls as the heart pumps it around the body. When the blood pressure is too high, it can damage your artery walls and some of your organs, especially your kidneys. When your blood pressure is taken there are two numbers recorded, for example 130/70. Both numbers are important.
The first number is called the systolic pressure – this is the pressure in the arteries as the heart squeezes out blood during a beat. The second number is called the diastolic pressure – this is the pressure of the blood in the arteries when the heart relaxes before the next beat. A normal blood pressure is considered to be anything less than 140/90. Your doctor will talk to you about your blood pressure and whether you need to do something about it. Sometimes your doctor will want your blood pressure to be lower than 140/90. It is important to know that your blood pressure does change and can be different from day to day.
Creatinine – normal range 45 -90 umol/L.
This is the most common test used to measure kidney function. Creatinine is a normal waste product from the breakdown of protein in muscles which is removed from the body by the kidneys. If the kidneys are not working well, there is more creatinine in the blood.
eGFR test (estimated Glomerular Filtration Rate) – normal >90mL/min/1.73m2.
When you have a blood creatinine test, the laboratory works out the eGFR from the same test. Many laboratories only report eGFR as >60 mL/min/1.73m² as results are not accurate between 6090mL/min/1.73m². An eGFR gives an estimate of the percentage of normal kidney function that you have. For example, an eGFR of 30 mL/min/1.73m² is equal to about 30% of your kidneys working. Kidney function naturally declines with age and values below the normal range may be entirely appropriate for some people.
HBA1c (glycosylated haemoglobin level), a common test for people with diabetes- normal <41 mmol/mol.
This blood test measures your average blood glucose over the previous weeks and gives an indication of your longer-term blood glucose control. The test is used as a regular monitoring tool if you have been diagnosed with diabetes. You should have this test every three months if you are diabetic. Urine test for protein. (There are two tests that your doctor may have done):
ACR – Albumin/creatinine ratio – normal <35 mg/mmol for females <25 mg/mmol for males
PCR – Protein/creatinine ratio – normal <40 mg/mmol for males <60 mg/mmol for females.
These tests check the amount of albumin (a type of protein) or total protein in the urine compared to the amount of creatinine. The urine protein test is a good way of picking up any kidney damage.
We recommend screening tests for chronic kidney disease in high-risk groups, such as people with diabetes or high blood pressure. Kidney disease runs in families and so close family members may also want to have their kidney function tested. Being diagnosed with kidney disease before it has progressed gives you the best chance to control the disease. Knowing your numbers will let you know how you are doing.
How to get your numbers?
Ask your doctor or the practice nurse for a kidney check. They will check your blood pressure and will give you a form to take to the lab to have a blood test, to check how well your kidneys are working.
Ask for a copy of your results. These can be sent to you either by email or post. Tell the person taking your tests that you would like a copy. Ask to sit down and go through your blood results with your doctor or nurse so you understand what they mean and check you have the results correct and any areas you can improve on.
What other tests might you have on your blood form?
- Urea – is a waste product produced in the liver and removed by the kidney’s electrolytes – these include sodium – is regulated by the kidneys. Body fluid and electrolyte balance are important measures of kidney function.
- Potassium – is controlled by the kidneys. It is critical for the proper functioning of the nerves and muscles, particularly the heart.
- Chloride – is involved in maintaining the proper balance of body fluids and the body’s acid levels.
- Calcium – is controlled in the blood by the parathyroid glands and the kidneys.
- Phosphate – is regulated by the kidneys. High levels may indicate kidney disease.
- Albumin – is a type of protein in your blood.
- Glucose – a measure of the sugar level in your blood.
- Uric Acid – is a normal substance got rid of in the urine. High levels can indicate gout, arthritis, and kidney problems.
- Cholesterol – is a fat-like substance which, if high, can cause heart disease.
- Haemoglobin – is the amount of oxygen-carrying protein contained within the red blood cells. Abnormal levels may indicate anemia (low blood count), red blood cell breakdown, or vitamin deficiencies.
- Red Blood Count – the total number of red blood cells.
- White Blood Count – the total number of white blood cells. Abnormal levels could mean an infection.