Urea explained

The end product of protein breakdown. The liver makes it, the kidneys remove it. Unlike creatinine it is affected by a good deal more than kidney function — dehydration, a high-protein diet, bleeding into the gut and some medicines all move it, which is why kidney function is not judged on urea alone. Urea up, creatinine barely moved: Usually dehydration rather than kidney damage — the kidney reabsorbs more water, and more urea with it.

Fasting: Not needed for urea itself. Best time: Any time, usually with the rest of the panel. Avoid beforehand: A very high-protein meal the day before. Be normally hydrated — this is the measurement most distorted by arriving thirsty.

Commonly: dehydration, which raises it more than creatinine; a high-protein diet; bleeding in the upper digestive tract; reduced kidney function; liver disease and pregnancy, which lower it. A single result is not a diagnosis. Values are read against the laboratory's own reference range and alongside your history, your symptoms and the rest of the panel — which is why every package includes a doctor to go through them with you.

At Smart Care Polyclinic, 29 Doha Centre, Al Maktoum Rd, Deira, Dubai. Walk in during opening hours or call +971 (0)4 379 3562.