Urea (Serum)
Serum urea measures the waste product urea directly in your blood. Urea forms in the liver when protein is broken down and is removed by the kidneys.
Like BUN (which measures just the nitrogen portion of the same molecule), serum urea reflects kidney filtering, hydration, and protein turnover. Some regions report urea rather than BUN; the two describe the same thing on different scales.
A raised urea level may point to reduced kidney clearance, dehydration, a high-protein intake, or increased protein breakdown. It's best understood alongside creatinine and your clinical context, not in isolation.
Lower urea can reflect a low-protein diet, overhydration, or liver conditions, and is frequently not a concern on its own.
Reference ranges differ by lab and units (often reported in mmol/L). Your clinician can interpret your specific value.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.