What is a urea and electrolytes (U and E) test?

A U and E test is commonly used to detect abnormalities of blood chemistry, primarily kidney (renal) function and dehydration.

How is a U and E test performed?

The U and E test is a blood test and requires a few millilitres of blood from a vein. In newborn babies blood may be taken from a heel-prick sample.

Why would you need a U and E test?

U and E is usually performed to confirm normal kidney function or to exclude a serious imbalance of biochemical salts in the bloodstream. A diverse number of conditions may be detected on the U and E test, as each parameter tested may be high or low. These conditions include:

  • Hyponatraemia (low sodium)
  • Hypernatraemia (high sodium)
  • Hypokalaemia (low potassium)
  • Hyperkalaemia (high potassium)
  • Metabolic acidosis (low bicarbonate)
  • Metabolic alkalosis (high bicarbonate)
  • Dehydration (high urea and/or creatinine)
  • Renal (kidney) impairment or failure (high urea and/or creatinine)
  • Gastrointestinal bleeding (high urea)
  • Hypoglycaemia (low glucose)
  • Hyperglycaemia (high glucose)

Each of these conditions in turn have several possible causes.

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U&E test results explained

Abnormal levels of urea can signal either short term or chronic kidney issues.

Common causes of electrolyte imbalance include:

  • Kidney disease
  • Illnesses with symptoms that cause fluid loss/dehydration (e.g. vomiting, diarrhea, sweating)
  • Intestinal/digestive issues
  • Hormone imbalance
  • Medications like antibiotics, diuretics and those used to treat cancer and heart disease

Always discuss your test results and what they mean for you with your doctor.

Related specialists

Related procedures

  • Pre-operative Anaesthetic assessment

Related tests

  • Sodium (Na)
  • Potassium (K)
  • Chloride (Cl)
  • Biocarbonate (HCO3, Bicarb)
  • Urea (U)
  • Creatinine (Cr)
  • Glucose (glu)

Also known as

  • Urea, electrolytes & creatinine (UEC)
  • Creatinine, urea, electrolytes & glucose (CUEG)
  • Electrolytes routine biochemistry


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This article is for informational purposes only and should not be taken as medical advice. If in doubt, HealthEngine recommends consulting with a registered health practitioner.

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