Blood draw
BUN (Urea Nitrogen) and Creatinine
BUN and creatinine; renal function.
€ 26,00
All tests
Kidneys and electrolytes · Blood
Urea nitrogen (BUN)
An American way of reporting urea in the blood; in the Netherlands the same value is reported as urea.
At a glance
- Measured in blood
- In 2 test panels
- No special preparation
Explanation
Urea nitrogen (BUN): what is measured?
Urea nitrogen, in English blood urea nitrogen (BUN), is not measured separately but calculated from urea. The laboratory measures urea and calculates how much nitrogen it contains, usually expressed in milligrams per deciliter (mg/dl). This is a unit used mainly in the United States. In the Netherlands, laboratories report urea itself, in millimoles per liter (mmol/l). BUN and urea therefore give the same information in a different number and a different unit.
What can it detect?
- Reduced kidney function, together with creatinine and eGFR
- Dehydration or reduced blood flow to the kidneys
- Increased breakdown of protein, for example with a protein-rich diet
Result
What does the result mean?
Urea nitrogen (BUN) too high
A raised BUN means the same as a raised urea. There are often harmless causes: drinking too little, heavy exertion or a protein-rich diet. The value also rises if the kidneys receive less blood flow, such as with dehydration or heart problems, with an obstructed urine outflow, with bleeding in the stomach or intestine and with reduced kidney function. If creatinine and eGFR are normal, a slightly raised BUN is usually not a sign of kidney damage.
Urea nitrogen (BUN) too low
A low BUN means the same as a low urea and is usually no cause for concern. It occurs with little protein in the diet and with drinking a lot. Rarely, a low value fits malnutrition or a liver that does not break down proteins properly.
After an abnormal result
If needed, the GP converts the BUN to urea and assesses the value together with creatinine, eGFR, drinking, diet and medicines. If only the BUN is slightly raised, a repeat measurement usually follows. If creatinine or eGFR is also abnormal, the approach of the Dutch GP guideline (NHG) on chronic kidney damage follows.
Reliability
How reliable is the test?
The BUN adds nothing beyond urea: it is the same measurement, converted to a different unit. Kidney function is assessed with the eGFR, which is calculated from creatinine. Because Dutch reference values are in mmol/l urea, a BUN result in mg/dl is hard to compare with earlier results at the GP. Just like urea, the value depends strongly on eating, drinking and protein breakdown.
What can affect the result?
- Protein-rich food, protein supplements, heavy exertion and drinking too little raise the value without the kidneys working any worse.
- The result is given in an American unit (mg/dl); comparing it with Dutch urea results requires a conversion.
- The reference values differ between laboratories and are often based on an American population.
- A normal value does not rule out reduced kidney function.
Who it is for
Who is the test useful for?
Useful for
Useful as an addition to creatinine and eGFR with risk factors for kidney damage, such as diabetes, high blood pressure or medicines that put strain on the kidneys. The BUN is mainly reported in panels that follow the American approach; if you want to compare the result with your GP, urea in mmol/l is more useful. In healthy adults without symptoms or risk factors, the chance of reduced kidney function is small; a slightly raised BUN is then more often due to diet or drinking too little.
How common is it?
There is no Dutch figure for how often an abnormal BUN or an abnormal urea occurs. According to the Dutch GP guideline (NHG), chronic kidney damage occurs in about 1 in 10 adults, more often at older age. A slightly raised value due to drinking little or protein-rich food is more common than kidney damage.
The NHG guideline on chronic kidney damage; the NVKC, allesovertesten.nl
Drawbacks and risks
- The American unit and reference values can cause confusion when comparing with Dutch results.
- A slightly raised value due to protein-rich food or drinking too little can cause unfounded worry about the kidneys.
Get tested
Urea nitrogen (BUN): test panels
Urea nitrogen (BUN) is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and resultsMore explanations
Other tests: Kidneys and electrolytes
- BUN/creatinine ratio
- Chloride
- CO2 (bicarbonate)
- Creatinine
- Creatinine (urine)
- Cystatin C
- eGFR
- Phosphate (inorganic)
- Potassium
- Sodium
- Urea