Biomarker . Patient guide
Urea Blood Test
What is Urea
Urea is a waste product made by the liver when protein is broken down, and it is cleared by the kidneys. Measured alongside creatinine and electrolytes (a U&E), it gives a picture of kidney function and hydration.
This biomarker entry is being clinically reviewed by our team. The factual content draws on UK guidance (NICE, NHS, Royal Colleges and the relevant speciality society where cited).
Reference range
Reported in mmol/L. Final reports always carry the issuing laboratory's range, which is what your clinician will interpret against.
| Group | Range | Note |
|---|---|---|
| Adults | 2.5 to 7.8 | mmol/L; varies between labs |
What it is
Protein metabolism produces ammonia, which the liver converts to urea for safe excretion by the kidneys. Blood urea therefore reflects the balance of protein breakdown, hydration, and kidney clearance, which is why it is interpreted together with creatinine rather than alone.
Why a clinician would order it
Urea is checked to assess kidney function, hydration and, in some settings, gastrointestinal bleeding (which raises urea disproportionately). It is a standard part of a U&E and a general health screen.
If your level is outside the range
Symptoms of low Urea
What low can indicate. Low protein intake, liver disease (reduced urea production), overhydration, or pregnancy.
Symptoms of high Urea
- Often none when mildly raised
- With significant kidney impairment: tiredness, poor appetite, nausea
What high can indicate. Dehydration (the commonest cause of a mild rise), reduced kidney function, a high-protein diet, or an upper gastrointestinal bleed. A urea raised out of proportion to creatinine usually points to dehydration or GI bleeding rather than intrinsic kidney disease.
Testing tips
No fasting needed. Hydration status strongly affects the result, so a raised urea with a normal creatinine is often simply dehydration and worth repeating after rehydrating.
Where you can get this tested
Urea is included in the following WMG Health panels. Same-day appointments at our Harley Street clinic, with results clinician-reviewed.
Want a specific combination of markers we do not have a panel for? Build a custom panel and our clinicians will design one for you.
Looking to book a test?
Comprehensive private health screening
Full blood screening at 134 Harley Street, London, reviewed by GMC-registered doctors with a written interpretation.
Symptoms often investigated with Urea
Urea is commonly tested when patients present with the following symptoms. If any of these resonate with you, the linked guides explain what to look for and which test pathway is appropriate.
Sources
UK guidance our clinicians use when interpreting this marker.
This page is general patient information, not personal medical advice. A GMC-registered clinician will review your results and tailor any interpretation to you. See our Editorial Policy for how we write and review content.
Common questions about Urea
What is a normal Urea range?
Adults: 2.5 to 7.8 (mmol/L; varies between labs). Always interpret your own results against the laboratory range printed on your report, since assay-specific reference ranges vary.
What does a low Urea result mean?
Low protein intake, liver disease (reduced urea production), overhydration, or pregnancy.
What does a high Urea result mean?
Dehydration (the commonest cause of a mild rise), reduced kidney function, a high-protein diet, or an upper gastrointestinal bleed. A urea raised out of proportion to creatinine usually points to dehydration or GI bleeding rather than intrinsic kidney disease.
Do I need to fast or prepare for the Urea blood test?
No fasting needed. Hydration status strongly affects the result, so a raised urea with a normal creatinine is often simply dehydration and worth repeating after rehydrating.
Can I order a Urea blood test privately in London?
Yes. WMG Health offers Urea in several standard panels and as part of a custom panel at our 134 Harley Street clinic. Results are released as each marker is reviewed, and the completion date is set by the slowest marker in your panel. We confirm the expected timeframe at booking. Book a standard panel online, or ask for a custom panel via /contact/ or 020 3239 3378.