Blood Urea Nitrogen
How It Feels
The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
There is very little chance of a problem from
having a blood sample taken from a vein.
- You may get a small bruise at the site. You can
lower the chance of bruising by keeping pressure on the site for several
- In rare cases, the vein may become swollen after the blood
sample is taken. This problem is called phlebitis. A warm compress can be used
several times a day to treat this.
- Ongoing bleeding can be a
problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and
other blood-thinning medicines can make bleeding more likely. If you have
bleeding or clotting problems, or if you take blood-thinning medicine, tell
your doctor before your blood sample is taken.
A blood urea nitrogen (BUN) test measures
the amount of nitrogen in your blood that comes from the waste product
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
6–25 with 15.5 being the best value.
- A high BUN value can mean kidney injury or
disease is present. Kidney damage can be caused by
high blood pressure that directly affects the kidneys.
High BUN levels can also be caused by low blood flow to the
kidneys caused by
- Many medicines may cause a
high BUN. Be sure to tell your doctor about all the nonprescription and
prescription medicines you take.
- A high BUN value may be caused by
a high-protein diet,
Addison's disease, tissue damage (such as from severe
burns), or from bleeding in the gastrointestinal tract.
BUN-to-creatinine ratios occur with sudden (acute) kidney failure, which may be
shock or severe dehydration. A very
high BUN-to-creatinine ratio may be caused by bleeding in the
digestive tract or
respiratory tract .
- A low BUN value may be caused by a diet very
low in protein, malnutrition, or severe liver damage.
excessive amounts of liquid may cause overhydration and cause a low BUN
- Women and children may have lower BUN levels than men
because of how their bodies break down protein.
- A low
BUN-to-creatinine ratio may be caused by a diet low in protein, a severe muscle
cirrhosis, or syndrome of inappropriate antidiuretic
hormone secretion (SIADH).