Kidney function tests

What are kidney function tests?

Kidney function tests are a group of blood tests that provide information on how well your kidneys are working.

Most people have 2 kidneys. They’re part of your urinary system. Kidneys have several important functions:

• filtering and cleaning your blood to remove waste products into urine (wee)
• balancing the fluids and salts or minerals in your body
• making vitamin D
• making hormones that help to control your blood pressure

Kidney function tests can help your doctor check your kidney function and to monitor it over time.

Kidney function tests are also known as renal function tests and include: urea and electrolytes tests. These are often shortened to: U&E, EUC or UEC.

The tests measure levels of various substances in your blood, including:

• electrolytes: sodium, potassium, chloride, bicarbonate
• minerals: phosphorus, calcium
• protein: albumin
• waste products: urea, creatinine
• glucose (sugar)

Your doctor might calculate your estimated glomerular filtration rate (eGFR). This is a measure of the amount of blood that’s filtered by your kidneys each minute. This is a good indicator of how well your kidneys are working. The calculation uses your age, sex, weight and blood creatinine level.

Your urine may also be tested for protein.

Why would I need kidney function tests?

Your doctor might request these tests if you:

• have kidney disease, to monitor and manage your treatment
• have high blood pressure or heart disease
• are living with diabetes
• are taking medicine that might affect your kidneys
• might have abnormal levels of potassium or other minerals in your blood

Kidney function tests are used as a screening test if you’re at risk of kidney disease.

How should I prepare for my kidney function tests?

You may be told to fast (not eat or drink) before your blood test. Check with your doctor if this is needed. You should also check how long you need to fast for.

Understanding your results

If your kidneys are not working properly, waste products can build up in your blood. This is bad for your health and can even become life-threatening.

The right mix of minerals, proteins, and glucose (sugar), in the blood is important for your nerve and muscle function.

Many diseases can harm your kidneys, for example diabetes and hypertension (high blood pressure).

It’s important to discuss your kidney function test results with your doctor to see what they mean for you.