"BUN" redirects here. For other uses, see Bun (disambiguation).
Blood urea nitrogen |
Diagnostics |
Urea
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MeSH |
D001806 |
LOINC |
6299-2, 59570-2, 12961-9, 12963-5, 12962-7 |
The liver produces urea in the urea cycle as a waste product of the digestion of protein. Normal human adult blood should contain between 6 to 20 mg of urea nitrogen per 100 ml (6–20 mg/dL) of blood. Individual laboratories will have different reference ranges as the assay used will vary between laboratories.[1][2]
Contents
- 1 Interpretation
- 2 Units
- 3 See also
- 4 References
- 5 External links
Interpretation
Blood urea nitrogen (BUN) is an indication of renal (kidney) health. The normal range is 1.8-7.1 mmol/L or 6–20 mg/dL.
The main causes of an increase in BUN are: high protein diet, decrease in glomerular filtration rate (GFR) (suggestive of renal failure) and in blood volume (hypovolemia), congestive heart failure, gastrointestinal hemorrhage,[3] fever and increased catabolism. Hypothyroidism can cause both decreased GFR and hypovolemia, however BUN-to-creatinine ratio has been found to be lowered in hypothyroidism and raised in hyperthyroidism.
The main causes of a decrease in BUN are severe liver disease, anabolic state, and syndrome of inappropriate antidiuretic hormone.[3]
Reference ranges for blood tests, comparing urea (yellow at right) to other blood constituents.
Another cause of a decreased BUN is ornithine transcarbamylase deficiency, which is a genetic disorder inherited in an X-linked recessive pattern. OTC Deficiency is also accompanied by hyperammonemia and high orotic acid levels.
Units
BUN (urea-N) is mg/dL in the United States, Mexico, Italy, Austria, and Germany. Elsewhere, the concentration of urea is reported as mmol/L, generally depending on the lab.
To convert from mg/dL of blood urea nitrogen to mmol/L of urea, multiply by 0.357 (each molecule of urea having 2 nitrogens, each of molar mass 14g/mol) (BUN is the mass of nitrogen within urea/volume, not the mass of urea)
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- Urea [mmol/L] = BUN [mg/dL of nitrogen] x 10 [dL/L] / 14x2 [mg N/mmol urea] (the mass of nitrogen within urea is used)
convert BUN to urea in mg/dL by using following formula:
-
- Urea [mg/dL]= BUN [mg/dL] * 2.14
(conversion factor derived by: MW of urea = 60, MW of urea nitrogen = 14x2 => 60/28 = 2.14)
factor = 1 for conversions in mmol (1 mole N2 = 2 moles N per mole of urea):
-
- BUN [mmol/L]= urea [mmol/L]
See also
- BUN-to-creatinine ratio
- Kt/V
- Urea reduction ratio (URR)
- Urine urea nitrogen
- Standardized Kt/V
References
- ^ Last page of Deepak A. Rao; Le, Tao; Bhushan, Vikas (2007). First Aid for the USMLE Step 1 2008 (First Aid for the Usmle Step 1). McGraw-Hill Medical. ISBN 0-07-149868-0.
- ^ Normal Lab Results from Marshal University School of Medicine
- ^ a b Longo et al., Harrison's Principles of Internal Medicine, 18th ed., p.611
External links
References ranges for blood tests (CPT 82000–84999)
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Electrolytes |
- Sodium
- Potassium
- Chloride
- Calcium
- Renal function
- Creatinine
- Urea
- BUN-to-creatinine ratio
- Plasma osmolality
- Serum osmolal gap
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Acid-base |
- Anion gap
- Arterial blood gas
- Base excess
- Bicarbonate
- CO2 content
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Iron tests |
- Ferritin
- Serum iron
- Transferrin saturation
- Total iron-binding capacity
- Transferrin
- Transferrin receptor
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Hormones |
- ACTH stimulation test
- Thyroid function tests
- Thyroid-stimulating hormone
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Metabolism |
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Cardiovascular |
- Cardiac marker
- CPK-MB test
- Lactate dehydrogenase
- Myoglobin
- Glycogen phosphorylase isoenzyme BB
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Liver function tests |
- Proteins
- Human serum albumin
- Serum total protein
- ALP
- transaminases
- Bilirubin
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Pancreas |
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Index of the urinary system
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Description |
- Anatomy
- Physiology
- Development
- Cells
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Disease |
- Electrolyte and acid-base
- Congenital
- Neoplasms and cancer
- Other
- Symptoms and signs
- Urine tests
- Blood tests
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Treatment |
- Procedures
- Drugs
- Intravenous fluids
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Index of hormones
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Description |
- Glands
- Hormones
- thyroid
- mineralocorticoids
- Physiology
- Development
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Disease |
- Diabetes
- Congenital
- Neoplasms and cancer
- Other
- Symptoms and signs
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Treatment |
- Procedures
- Drugs
- calcium balance
- corticosteroids
- oral hypoglycemics
- pituitary and hypothalamic
- thyroid
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Index of the heart
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Description |
- Anatomy
- Physiology
- Development
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Disease |
- Injury
- Congenital
- Neoplasms and cancer
- Other
- Symptoms and signs
- Blood tests
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Treatment |
- Procedures
- Drugs
- glycosides
- other stimulants
- antiarrhythmics
- vasodilators
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Index of digestion
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Description |
- Anatomy
- Physiology
- Development
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Disease |
- Congenital
- Neoplasms and cancer
- Inflammatory bowel disease
- Gluten sensitivity
- Other
- Symptoms and signs
- Blood tests
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Treatment |
- Procedures
- Drugs
- anabolic steroids
- antacids
- diarrhoea and infection
- bile and liver
- functional gastrointestinal disorders
- laxatives
- peptic ulcer and reflux
- nausea and vomiting
- other
- Surgery
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