Last Updated on October 22, 2025 by Analgesia team
U & E Medical Abbreviation
A urea and electrolytes (U&E) blood test, also known as a kidney function test, measures the levels of various substances in your blood to assess your kidney function and fluid and electrolyte balance:
- Electrolytes: Sodium, potassium, chloride, and bicarbonate, which help maintain fluid balance and plasma volume. Abnormal levels can cause abnormal heart rhythms.
- Urea: A protein that is normally broken down by the kidneys. High levels of urea in the blood could indicate kidney problems.
- Other substances: Phosphorus, calcium, albumin, and creatinine.
When is U&E test performed?
A Urea and Electrolytes (U&E) test is a common blood test that checks how well your kidneys are working and whether your body’s fluid and mineral balance is normal. It’s often requested in a variety of medical situations, including:
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As part of a routine health check-up, especially if you’re having general blood work done or are over 40.
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To monitor ongoing conditions such as diabetes, high blood pressure, or heart disease, which can affect kidney function over time.
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Before starting certain medications, particularly those that can impact the kidneys (for example, ACE inhibitors, diuretics, or some antibiotics).
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To investigate symptoms of kidney problems — such as fatigue, swelling, confusion, or changes in urination.
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To check for acute kidney injury (AKI) or dehydration after illness, surgery, or fluid loss.
Getting your results
Blood test results for U&E usually take around 7 working days to come back, though more specialised tests may take longer.
If you’re registered for online GP services, you can often view your results digitally.
If your doctor needs to discuss them with you, they’ll arrange an appointment or phone consultation.
Normal ranges for U and E test results
Normal reference ranges can vary slightly between laboratories, but generally include:
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Adults: 6 – 7.1 mmol/L (SI units) or 10 – 20 mg/dL
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Older adults: Levels may be slightly higher due to reduced kidney function with age
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Children and infants: 5 – 18 mg/dL
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Newborns: 3 – 12 mg/dL
These values reflect urea levels in the blood. Electrolytes such as sodium, potassium, and chloride are also reported as part of the test, giving doctors a fuller picture of kidney health and fluid balance.
Abnormal U&E result
Abnormal urea and electrolytes (U&E) test results can indicate kidney problems, heart arrhythmias, or other health issues.
What can cause abnormal U&E results?
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- Kidney disease
- Dehydration or overhydration
- Illnesses that cause fluid loss, like vomiting, diarrhoea, or sweating
- Intestinal or digestive issues
- Hormone imbalance
- Medications like antibiotics, diuretics, and some heart and cancer medications
What Does U & E Check For?
A&E blood tests can check for a range of conditions, including HIV, hepatitis B and C, electrolyte imbalances, and kidney dysfunction.
HIV, hepatitis B, and C
- These tests are routinely performed on patients aged 16 and over who have a blood test in an A&E department in the UK.
- The tests are free and confidential.
- Early diagnosis of these conditions is important as treatment is life-saving.
Electrolyte imbalances
- These tests measure the levels of electrolytes in the blood, such as sodium, potassium, and chloride.
- Electrolyte imbalances can cause a range of symptoms, from mild to severe.
- Abnormal levels of electrolytes can also cause abnormal heart rhythms.
Kidney dysfunction
- These tests measure the levels of blood urea nitrogen (BUN) and creatinine in the blood.
- Kidney dysfunction can manifest with a range of symptoms, from mild to severe.
Other conditions
- U & E blood tests can also check for cholesterol levels, blood gas balance, and complete blood count (CBC).
What other kidney function tests are there?
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Creatinine testsMeasure the level of creatinine in your blood, which is filtered out by the kidneys. Higher levels of creatinine indicate kidney dysfunction.
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Estimated Glomerular Filtration Rate (eGFR)A mathematical calculation that estimates kidney function based on serum creatinine levels, age, sex, and race.