High BUN Level

Blood Urea Nitrogen (BUN) is the final metabolic product of protein in the body. It is mainly excreted through glomerular filtration. The value of BUN can reflect the condition of kidney function.

For the normal people, the fasting BUN is 3.2-7.1 mmol/L (9-20mg/dL). If people have kidney lesion， such as Glomerulonephritis, Interstitial Nephritis, Acute and Chronic Kidney Failure, kidney destructive lesion, all these diseases can lead to BUN increasing. There are also many other factors except for kidney factors leading to BUN increasing. If it can exclude other factors, the BUN 21.4 mmol/L (60mg/dL) will be one of the indicators for Uremia.


For patients, there are two conditions of high BUN level. The most common is kidney insufficiency, including Acute Kidney Insufficiency and Chronic Kidney Insufficiency. The first reason is because of kidney damage, BUN can’t be eliminated with Urine, and a part of patients with Acute Nephritis, Nephrotic Syndrome can also appear transient BUN increasing, mainly in serious swelling. Because little urination lead to no discharge of BUN with urine, and these BUN will accumulate in the blood.