Kidney Function Test (U&Es)🧪 Kidney Function Test (U&Es)
Monitors kidney efficiency, fluid balance, and electrolyte levels.
🔍 What is it?
A Kidney Function Test, commonly referred to as U&Es (Urea and Electrolytes), is a blood test that evaluates how well your kidneys are working. It checks for signs of kidney dysfunction, dehydration, and electrolyte imbalances that could affect your health.
This test is often done as part of a routine check-up or if you have symptoms of kidney problems.
📊 What does it measure?
| Marker | What it tells you |
| Urea | A waste product filtered by the kidneys. Elevated levels may suggest dehydration or kidney impairment. |
| Creatinine | A waste product from muscle breakdown. High levels indicate reduced kidney filtration. |
| eGFR (Estimated Glomerular Filtration Rate) | A calculation based on creatinine, age, sex, and ethnicity. It estimates how well your kidneys are filtering. |
| Electrolytes (Sodium, Potassium, Chloride, Bicarbonate) | These help maintain fluid balance, nerve function, and muscle activity. Imbalances can indicate kidney or hormonal issues. |
❓ Why might I need it?
You might need this test if you:
- 😴 Feel persistently tired or weak
- 🦵 Experience swelling in the legs or ankles
- ❤️ Have high blood pressure or diabetes
- 💧 Are dehydrated or have had vomiting/diarrhoea
- 💊 Take medications that affect the kidneys (e.g. NSAIDs, ACE inhibitors)
- 🩺 Are being monitored for a chronic condition like chronic kidney disease (CKD)
- 🛌 Are undergoing surgery or a general health assessment
🧬 Conditions it can help detect:
- Chronic kidney disease (CKD)
- Acute kidney injury (AKI)
- Dehydration
- Electrolyte imbalances
- Urinary tract obstruction
- Complications from diabetes or hypertension
⏱️ How is it done?
- A small sample of blood is taken from a vein in your arm
- The process takes just a few minutes
- Results are typically available within 1–2 days
💷 Typical private cost in the UK:
- Approximately £40–£85
Often included in general health or fatigue panels
✅ Commonly combined with:
- Full Blood Count (FBC)
- Liver Function Test (LFT)
- Thyroid Function Test
- Blood Glucose or HbA1c (for diabetes risk)
Urinalysis (for protein or blood in urine)
📚 References:
- NHS UK – Kidney function tests
- Patient.info – Urea and Electrolytes (U&E)
- Bupa UK – Kidney function test
- National Kidney Foundation (UK page) – Understanding eGFR