What it measures
Urea is a waste product made in the liver when protein is broken down. The kidneys clear it into the urine, so the level in the blood is read with creatinine to check kidney function and hydration.
Why people test it
- Part of a kidney function test, alongside creatinine, sodium and potassium.
- Rises with dehydration, so it helps show whether someone is short of fluid.
- Monitored on medicines that affect the kidneys or the body's fluid balance, such as diuretics.
- A high-protein diet can raise urea, as can dehydration after long or hot sessions.
Typical range
Ranges vary between labs, with the method used, age and sex, and your report shows the lab's own range. One NHS trust lab gives 2.5 to 7.8 mmol/L for adults. Source: Oxford University Hospitals NHS Foundation Trust: biochemistry reference ranges.
Finger-prick or vein?
A finger-prick sample is usually fine for urea. A vein draw works too and is used when it is part of a larger panel.