Hi sir. I have given my blood sample for test. And I got reports. In that reports there is a bun (blood urea nitrogen) test. In that the bun calculated value is showing as 7.45 I did not understand what is that value. And it is normal.

Dr. Sajeev KumarGeneral Physician34yrs exp

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Blood urea nitrogen (bun) is a medical test that measures the amount of urea nitrogen found in the blood. The liver produces urea in the urea cycle as a waste product of the digestion of protein. Normal human adult blood should contain 7 to 20 mg/dl (2.5 to 7.1 mmol/l) of urea nitrogen. Individual laboratories will have different reference ranges as the assay used can vary between laboratories 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), decrease in blood volume (hypovolemia), congestive heart failure, gastrointestinal haemorrhage, fever, and increased catabolism. Hypothyroidism can cause both decreased gfr and hypovolemia, but 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 a severe liver disease, anabolic state, and syndrome of inappropriate antidiuretic hormone 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. Bun (urea-n) si unit is mmol/l bun [mmol/l] = bun [mg/dl] * 0.3571 to convert from mg/dl of blood urea nitrogen to mmol/l of urea, multiply by 0.357 (each molecule of urea having two nitrogens, each of molar mass 14g/mol) (bun is the mass of nitrogen within urea/volume, not the mass of urea) 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]  

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