What Is Urea?
Urea is a waste product formed in the liver when protein is broken down. It is carried in the blood to the kidneys, where it is filtered out and excreted in urine. Urea is the primary way the body eliminates excess nitrogen from amino acid metabolism.
A blood urea test (also called blood urea nitrogen or BUN in some countries) is one of the most widely used markers of kidney function. Along with creatinine and eGFR, it helps assess how effectively your kidneys are filtering waste from your blood.
Why Is Urea Tested?
Your doctor or health professional may request a urea test to:
- Assess kidney function alongside creatinine and eGFR
- Investigate symptoms of kidney disease such as fatigue, swelling, or reduced urine output
- Monitor existing kidney disease or kidney transplant function
- Evaluate dehydration — urea rises disproportionately to creatinine when dehydrated
- Monitor the effects of medications that may impair kidney function (NSAIDs, ACE inhibitors, diuretics)
- Assess nutritional status — very low urea can indicate malnutrition
- Investigate gastrointestinal bleeding (urea rises from digested blood proteins)
Normal Ranges
Urea is measured in mmol/L in the UK:
| Group | Normal Range (mmol/L) |
|---|---|
| Adults (18–60) | 2.5 – 7.8 |
| Adults (over 60) | 3.0 – 9.2 |
| Children | 2.5 – 6.5 |
| Pregnancy | 2.0 – 5.5 (physiologically lower) |
Reference ranges may vary between laboratories. Urea is best interpreted alongside creatinine and eGFR for a complete picture of kidney function.
Check Your Urea Levels at Home
The Core Health 45 includes Urea testing along with 44 other biomarkers. Results in 2 working days with a free at-home phlebotomist visit.
View Core Health 45 →Causes of High Urea
Elevated urea (uraemia) can result from:
- Kidney disease: Acute kidney injury or chronic kidney disease reduces urea clearance
- Dehydration: The most common cause of mildly raised urea — reduced blood flow to kidneys concentrates urea
- High-protein diet: Excessive protein intake increases urea production
- Gastrointestinal bleeding: Digested blood proteins are metabolised to urea in the liver
- Heart failure: Reduced cardiac output decreases kidney perfusion
- Urinary tract obstruction: Blocked ureters, enlarged prostate, or kidney stones
- Medications: Corticosteroids, tetracyclines, and some diuretics can raise urea
- Increased protein catabolism: Burns, trauma, sepsis, or fever increase protein breakdown
- Shock: Any cause of severely reduced blood flow to the kidneys
Causes of Low Urea
Low urea levels may indicate:
- Liver disease: The liver produces urea — severe liver damage reduces urea synthesis
- Malnutrition: Insufficient protein intake means less amino acid metabolism and less urea production
- Overhydration: Excessive fluid intake dilutes blood urea concentration
- Pregnancy: Increased blood volume and kidney filtration rate physiologically lower urea
- SIADH: Syndrome of inappropriate antidiuretic hormone causes fluid retention and dilutional low urea
- Very low-protein diet: Vegan or very low-protein diets may result in lower urea production
How to Maintain Healthy Urea Levels
- Stay well hydrated: Adequate water intake (1.5–2 litres daily) helps maintain healthy kidney perfusion and urea clearance
- Eat a balanced diet: Moderate protein intake (0.8–1.2g per kg body weight) supports healthy urea levels
- Protect your kidneys: Limit NSAID use, manage blood pressure, and control blood sugar if diabetic
- Monitor medications: Some drugs affect kidney function — discuss with your GP if your urea is consistently high
- Manage underlying conditions: Diabetes, hypertension, and heart disease all affect kidney function over time
- Limit excess protein supplements: Very high protein intake from supplements can elevate urea unnecessarily
- Exercise regularly: Moderate activity supports cardiovascular and kidney health
When Should You Get Tested?
Consider testing your urea levels if you:
- Have symptoms of kidney problems (fatigue, swelling, changes in urination)
- Have diabetes, high blood pressure, or heart disease — all risk factors for kidney disease
- Are taking medications that may affect kidney function
- Have a family history of kidney disease
- Are over 60 — kidney function naturally declines with age
- Experience persistent dehydration, nausea, or confusion
Which Lola Health Tests Include Urea?
Urea is included in several Lola Health blood test panels as part of a comprehensive kidney function assessment:
- Peak Insights — our most comprehensive panel with full kidney function markers plus 70+ biomarkers
- Vital Check — includes kidney function tests including urea, creatinine, and eGFR
- Core Health — essential health screening with kidney function assessment
Check Your Urea Levels
Get a comprehensive blood test from Lola Health with GP-certified results and personalised recommendations. All tests use venous blood draws for medical-grade accuracy.
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