Urea & Electrolytes
The Urea & Electrolytes test assesses kidney function, fluid balance, and essential mineral levels. It is commonly used to investigate dehydration, kidney disease, and electrolyte imbalance.
Turnaround time
1-2 days
Biomarkers count
1
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Details about Urea & Electrolytes
What is the Urea & Electrolytes test?
The Urea & Electrolytes (U&E) test is a blood test that evaluates how well the kidneys are functioning and whether the body’s fluid and electrolyte balance is stable. The kidneys play a key role in filtering waste, regulating blood pressure, and maintaining electrolyte levels.
This test typically measures urea, creatinine, sodium, potassium, chloride, and bicarbonate, and often includes an estimated glomerular filtration rate (eGFR). Together, these markers provide a clear picture of kidney health and internal chemical balance.
It is one of the most commonly requested blood tests in both routine and urgent clinical assessment.
Why do I need a Urea & Electrolytes test?
Electrolyte imbalances and kidney dysfunction can cause a wide range of symptoms and may develop silently. Early testing helps identify problems before complications arise.
You may need this test if you experience:
- Fatigue or weakness
- Dehydration or fluid retention
- Muscle cramps or irregular heartbeat
- Confusion or dizziness
- Reduced urine output
- High blood pressure
- Vomiting or diarrhoea
- Use of medications affecting kidneys or electrolytes
- Monitoring known kidney disease
The test helps determine whether symptoms are related to kidney function, hydration, or electrolyte imbalance.
Benefits of the test
- Assesses kidney function
Evaluates waste filtration and renal performance. - Detects dehydration or fluid overload
Sodium and urea reflect fluid balance. - Identifies electrolyte imbalance
Sodium and potassium are critical for nerve and muscle function. - Supports medication monitoring
Important when using diuretics or blood pressure treatments. - Useful in acute and chronic conditions
Widely used in routine and urgent care. - Monitors kidney disease progression
Helps track changes over time. - Simple blood-based testing
Requires only one blood sample. - Essential baseline health check
Often included in general health panels.
Step-by-step: How we offer testing
Clinic-based testing (UK-wide)
- Choose your nearest UK clinic
- Attend your appointment
- A clinician draws a blood sample
- Sample is sent to the laboratory
- Results are issued once analysis is complete
Home or hotel visit (+£60, UK-wide)
- Book a mobile phlebotomist
- Blood sample taken at your home or hotel
- No need to attend a clinic
- Sample securely transported to the laboratory
Your results explained
Low levels
- Low sodium – may cause confusion, headaches, weakness
- Low potassium – may affect muscle function and heart rhythm
- Low urea – often related to hydration or diet
Typical UK reference examples (may vary):
- Sodium: <135 mmol/L
- Potassium: <3.5 mmol/L
Normal levels
- Urea, electrolytes, creatinine, and eGFR within reference range
- Suggests normal kidney function and fluid balance
High levels
- High urea or creatinine – reduced kidney filtration or dehydration
- High potassium – may affect heart rhythm
- High sodium – often linked to dehydration
Typical UK reference examples:
- Sodium: >145 mmol/L
- Potassium: >5.0 mmol/L
- eGFR: <60 mL/min/1.73m² (reduced kidney function)
Results should always be interpreted together and in clinical context.
How It Works
Simple steps to get your results
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Choose your test online and book in seconds. Select your preferred clinic location or home visit option.
Visit or Test at Home
Attend one of our UK or London clinics, arrange a home nurse visit, or use a finger-prick kit where available.
Get Your Results
Your sample is analysed by accredited UK laboratories, with secure results delivered directly to you.
Take control of your health with London Blood Tests
WhatsApp UsHow to Prepare for Your Test
Follow these guidelines for accurate results
Sample Timing
Where possible, attend your blood test between 7am and 12pm. Please wait until any short-term illness or infection has fully resolved before testing. Avoid intense exercise for 24–48 hours beforehand, as this can affect certain markers.
Fasting & Hydration
Fasting is not always required, but some tests may recommend it. If fasting is advised, avoid food for 8–12 hours before your appointment and drink water only. Stay well hydrated, as this helps with sample collection and accuracy.
Medications & Supplements
Continue prescribed medications unless advised otherwise by your clinician. Avoid vitamin, mineral, or biotin supplements for at least 24–48 hours before your test, as these can interfere with results. If you are unsure about any medication or supplement, please let us know before your appointment.
Hormones & Menstrual Cycle
For hormone-related tests, timing within your menstrual cycle may be important. If relevant, follow any specific guidance provided on your test page.
If you have any questions or special circumstances, our team is happy to advise before your appointment.