Urea
A waste product of protein breakdown, cleared by the kidneys. Read with creatinine to gauge kidney function and hydration.
Typical reference range
| Range | Unit |
|---|---|
| 2.5–7.8 | mmol/l |
What Urea measures
Urea is a waste product formed when the body breaks down protein. On some lab reports it is listed simply as urea, while on others the same information appears as blood urea nitrogen, or BUN. The liver produces it, and the kidneys filter it out of the blood so it can leave the body in urine, which is why it is often used as one window onto how well the kidneys are working.
On its own, though, urea is not a pure kidney measure. It is strongly shaped by hydration, how much protein you eat, and several other factors. For this reason a clinician reads it alongside creatinine and eGFR, and the urea-to-creatinine ratio can offer a hint about what is driving a given result.
What a high Urea can mean
A high urea (or high BUN) can suggest reduced kidney function, but it very commonly reflects something outside the kidneys entirely, so the surrounding picture matters a great deal.
- Dehydration, one of the most frequent reasons urea drifts upward.
- A high-protein diet, since more protein breakdown means more urea produced.
- Gastrointestinal bleeding, where blood in the gut is broken down and absorbed.
- Certain medications that can raise the level.
Because hydration and diet influence it so heavily, a high urea paired with a normal creatinine often points toward a non-kidney cause rather than kidney disease. Clinicians interpret the value together with creatinine and eGFR and your wider context, so it is best to discuss the result with a clinician who can see the whole picture.
What a low Urea can mean
A low urea (or low BUN) is frequently not a cause for concern and is often explained by everyday factors rather than illness.
- A low-protein diet, which means less protein is broken down into urea.
- Overhydration, where extra fluid dilutes the level.
- Pregnancy, during which urea commonly runs a little lower.
Less commonly, because the liver is where urea is made, significant liver disease can reduce how much is produced and lower the result. That is one reason a low value is read in context rather than in isolation.
As with a high reading, a single number rarely tells the full story. It is best to discuss the result with a clinician who can weigh it against your diet, hydration, and other markers.
Track your Urea over time in Quanome — it reads your lab reports (PDF or photo) on your device, charts each marker against its range, and an AI coach explains what your trends mean alongside your Apple Health and DNA.