BUN normal ranges are age-related.
Adults:
18 to 30 years old: 9 - 20 mg/dl
30 to 40 years old: 9 - 21 mg/dl
40 to 50 years old: 9 - 22 mg/dl
50 to 60 years old: 9 - 25 mg/dl
60 to 70 years old: 9 - 28 mg/dl
More than 70 years old: 9 - 32 mg/dl
Children:
1 to 17 years old: 5.5 - 20 mg/dL
Newborns: 3 - 14 mg/dL
In the International System of Units (SI), BUN in the blood is measured in mmol/L. The normal BUN level in the SI is:
Adults:
18 to 30 years old: 3.21 - 7.14 mmol/l
30 to 40 years old : 3.21 - 7.5 mmol/l
40 to 50 years old: 3.21 - 7.85 mmol/l
50 to 60 years old: 3.21 - 8.92 mmol/l
60 to 70 years old: 3.21 - 10 mmol/l
More than 70 years old: 3.21 - 11.42 mmol/l L
Children:
1 to 17 years old: 1.96-7.14 mmol/l
Newborns: 1.07 - 5 mmol/l
Each laboratory must establish its own normal ranges for BUN in the blood. These ranges depend on the makeup of the local population, the technologies used and the accuracy of the measurement. There may be also slight differences in the normal levels according to age, gender, race or ethnic origin, geographic region, diet, type of sample and other relevant status.
Your doctor will study the results along with your medical record, screenings, physical condition, symptoms and any other relevant information about your situation.
There are some circumstances to take into account about BUN normal ranges in the blood:
Urea is the final product of protein metabolism. Urea appears in the liver as a waste product and carry to the bloodstream. Later, it is filtered by the kidneys and excreted in urine. If the kidneys do not work efficiently, the urea will stay in the blood in high concentration and it can damage organs and tissues.
In the US and in a few other countries, urea concentration measures only the amount of urea nitrogen. It reflects only the nitrogen content of urea and it is referred as blood urea nitrogen (BUN). Around the world urea measurements usually considers the whole molecule. For that reason, urea is approximately twice the BUN values:
Urea = BUN * 2.1428
Urea is a marker for kidneys and liver activity.
Urea level in the blood is directly related to nutrition, protein metabolism/catabolism and renal functionality.
A high level of BUN in the blood may be due to:
A BUN level below the normal range may be a sign of a low-protein diet or a liver disorder (the liver is not doing a proper protein metabolism). Some disorders related to a low BUN level in the blood are pregnancy and acromegaly.
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The following values are considered to be normal values:
IMPORTANT: These levels are expressed in mg/dl. They are an example of a healthy man of about 45 years of age with no known disease, not taking any medication and with an appropriate intake of protein in the diet. The ranges can be different depending on the laboratory or on your personal circumstances.
BUN | |||||||
|---|---|---|---|---|---|---|---|
| Normality | |||||||
| 9 mg/dl | 10 mg/dl | 11 mg/dl | 12 mg/dl | 13 mg/dl | 14 mg/dl | 15 mg/dl | 16 mg/dl |
| 17 mg/dl | 18 mg/dl | 19 mg/dl | 20 mg/dl | 21 mg/dl | 22 mg/dl | ||
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