What this marker measures
Urea and BUN measure the same biological substance but report it differently — Urea is the full-molecule reading (mmol/L), more common on European reports; BUN is the nitrogen-only reading (mg/dL), more common on US reports. Conversion: urea (mg/dL) ≈ BUN (mg/dL) × 2.14.
High or low: what it can mean
High Urea
Elevated urea can reflect reduced kidney filtration, dehydration, a high-protein diet, gastrointestinal bleeding, or increased protein breakdown. It is often reviewed with creatinine, eGFR, electrolytes, and clinical context — diagnosis usually requires confirmation and clinical context.
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Low Urea
Low urea can be associated with a low-protein diet, over-hydration, reduced urea production from the liver, or pregnancy.
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Frequently asked questions
What is Urea?
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Urea is the waste molecule formed when the liver breaks down protein. The kidneys filter it from blood, so the level reflects both protein turnover and kidney filtration.
What does Urea measure?
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Urea and BUN measure the same biological substance but report it differently — Urea is the full-molecule reading (mmol/L), more common on European reports; BUN is the nitrogen-only reading (mg/dL), more common on US reports. Conversion: urea (mg/dL) ≈ BUN (mg/dL) × 2.14.
What does high Urea mean?
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Elevated urea can reflect reduced kidney filtration, dehydration, a high-protein diet, gastrointestinal bleeding, or increased protein breakdown. It is often reviewed with creatinine, eGFR, electrolytes, and clinical context — diagnosis usually requires confirmation and clinical context.
What does low Urea mean?
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Low urea can be associated with a low-protein diet, over-hydration, reduced urea production from the liver, or pregnancy.
Related biomarkers
Editorial note
LabTestly explains lab markers using plain-English educational content. Reference ranges may vary by laboratory and should be interpreted with a clinician.
Educational content · Editorially reviewed for clarity · Last updated
Common sources used for lab-test education
Not medical advice
This page is for general understanding only and does not replace medical advice from your clinician. Reference ranges can vary by laboratory, age, sex, pregnancy status, medications, and clinical context.