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Summary
What is the U&E (urea, creatinine, electrolytes)?
U&E is a commonly ordered group of tests performed on the same sample of blood that checks how well your kidneys are working. Typically, it includes:
Urea and creatinine are waste products.
Your kidneys filter your blood, removing waste and water to make urine. The urine flows from your kidneys to your bladder to be disposed of. Healthy kidneys filter most waste products from your blood. Measuring levels of waste products in your blood can show how well your kidneys are working. For more on how your kidneys work see Kidney Function Tests (also known as the Renal Profile).
Urea is formed when your body breaks down protein. Healthy kidneys remove more than 90 per cent of the urea the body makes. Having high levels of urea suggests that your kidneys are not working as they should be. However, urea levels can be affected by many things such as your muscle mass and by the amount of protein in your diet, which means that measuring urea alone cannot give a diagnosis.
Creatinine is produced by your muscles as part of normal activity. Your kidneys filter almost all creatinine from your blood. Having high levels of creatinine in your blood suggests that your kidneys are not working well.
The eGFR is a calculation used to estimate the amount of blood filtered per minute by your kidneys. It uses the results from your creatinine test together with your age, body size and gender to come up with a number. It is regarded as the best way to determine how well your kidneys are filtering your blood.
Kidneys keep electrolyte levels in balance.
Electrolytes are minerals that carry an electric charge when dissolved in water. They help regulate many of your body’s systems including heart rhythms, nerves and muscles. All fluid and almost every cell in your body contains electrolytes and they help maintain the amount of fluid and the acid-base balance in your body. If your kidneys are not working properly the levels may be abnormally high or low.
Kidneys also work to keep electrolyte levels in the blood at a constant level no matter what changes take place in the body. They do this through the reabsorption of electrolytes into the blood or by getting rid of them through the urine.
Sodium and potassium maintain your body’s fluid balance. Potassium is responsible for the fluid inside your cells and sodium is responsible for fluid outside your cells, and under normal conditions they keep the fluid inside and outside your cells in balance.
Bicarbonate is a waste product formed when your body’s cells use oxygen. Bicarbonate passes from your cells into the blood where it attaches to haemoglobin in red blood cells and is transported back to your lungs. In your lungs, bicarbonate is separated from the haemoglobin and is breathed out as carbon dioxide. Levels of bicarbonate are adjusted by your kidneys to help maintain your body’s pH level and maintain electric neutrality.
Why get tested?
U&E is a group of routine blood tests that are ordered to check your kidney function and your general health. Sometimes, a U&E test will be ordered when it is suspected that you have a non-kidney health problem which is affecting levels of electrolytes. It is also ordered at regular intervals if you are having treatment for kidney disease. Your doctor may also order a U&E test before starting you on medication, especially blood pressure medication.
Having the test
Sample
Blood
Preparation
None
Your results
Reading your test report
Your results will be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.
Creatinine, urea and electrolytes (sodium, potassium, chloride, bicarbonate) are key markers for assessing kidney function and overall metabolic health.
| Test | Levels | Interpretation |
| Urea | Adult: 3.0 - 10.0 mmol/L | Normal results. |
| High: greater than 10.0 mmol/L | High urea levels can indicate reduced kidney function, dehydration, or increased protein intake. | |
| Low: less than 3.0 mmol/L | Low urea blood levels are seen with liver disease or malnutrition. | |
| Creatinine | Adult male: 60 – 110 μmol/L Adult female: 45 – 90 μmol/L | Normal results. Creatinine results are used to calculate your eGFR. |
| High: greater than 110 for males or 90 μmol/L for females | High creatinine levels suggest reduced kidney function, which can be due to conditions like chronic kidney disease, dehydration, obstruction, or muscle breakdown. | |
| Low: less than 60 for males or 45 μmol/L for females. | Low creatinine levels can be seen in cases of low muscle mass, advanced liver disease, or malnutrition. | |
| Sodium | Adult: 135 – 145 mmol/L. | Normal results. |
| High: greater than 145 mmol/L. | Elevated serum sodium levels typically result from loss of fluids from the body rather than excessive sodium intake. | |
| Low: less than 135 mmol/L. | Low serum sodium levels can result from various conditions affecting, body water balance, kidney function, and hormone changes. | |
| Potassium | Adult: 3.5–5.5 mmol/L. | Normal results. |
| High: greater than 5.2 mmol/L. | High serum potassium levels can result from increased potassium intake, impaired kidney function, changes in acid-base balance or potassium moving out of cells. | |
| Low: less than 3.5 mmol/L. | Low serum potassium levels can result from various conditions affecting body water balance, kidney function, and acid-base regulation. | |
| Chloride | Adult: 95–110 mmol/L. | Normal results. |
| High: greater than 110.0 mmol/L. | Elevated serum chloride is often associated with acid-base imbalances, dehydration, or kidney impairment. | |
| Low: less than 95 mmol/L. | Low serum chloride levels can result from various conditions affecting water balance, acid-base regulation, and electrolyte changes. | |
| Bicarbonate | Adult: 22–32 mmol/L. | Normal results. |
| High: greater than 32 mmol/L. | Elevated serum bicarbonate levels are often associated with metabolic alkalosis, a condition where the body's pH shifts toward alkalinity. | |
| Low: less than 22 mmol/L. | Low serum bicarbonate levels are typically seen with metabolic acidosis, where the body's acid-base balance shifts toward acidity. | |
| Please note: only adult reference intervals are given in this table. | ||
For information on specific results of test components see:
Reference Intervals
Your results will be compared to a reference interval (sometimes called a normal range or reference range).
If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation. Your results need to be interpreted by your doctor.
Questions to ask your doctor
The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.
You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.
Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods, medications or supplements. These may affect your results. Ask:
More information
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