Dehydration generally causes BUN levels to rise more than creatinine levels. This causes a high BUN-to-creatinine ratio. Kidney disease or blockage of the flow of urine from your kidney causes both BUN and creatinine levels to go up.
How It Is Done A health professional uses a needle to take a blood sample, usually from the arm. How It Feels When a blood sample is taken, you may feel nothing at all from the needle. Risks There is very little chance of having a problem from this test. Results Normal Each lab has a different range for what's normal.
High values A high BUN value can mean kidney injury or disease is present. Kidney damage can be caused by diabetes or high blood pressure that directly affects the kidneys. High BUN levels can also be caused by low blood flow to the kidneys caused by dehydration or heart failure. 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 , or tissue damage such as from severe burns , or from bleeding in the gastrointestinal tract. High BUN-to-creatinine ratios occur with sudden acute kidney problems, which may be caused by shock or severe dehydration.
A very high BUN-to-creatinine ratio may be caused by bleeding in the digestive tract or respiratory tract. Low values A low BUN value may be caused by a diet very low in protein, by malnutrition, or by severe liver damage. Drinking too much liquid may cause overhydration and cause a low BUN value.
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 injury called rhabdomyolysis , pregnancy, cirrhosis , or syndrome of inappropriate antidiuretic hormone secretion SIADH. Our goal is to not have a single piece of inaccurate information on this website. If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please leave a comment or contact us at support selfhacked.
Note that each number in parentheses [1, 2, 3, etc. Testing urea levels in the blood provides information about your health. This post covers the causes of high and low blood urea nitrogen BUN and what they may mean for you. Blood urea nitrogen BUN is a measure of the amount of urea in the blood [ 1 ]. The liver produces urea as a waste product of proteins breakdown.
It binds excess nitrogen from used-up proteins and safely removes it from the body [ 1 , 2 ]. Urea is created not only from dietary protein, but also from protein in your tissues [ 3 ]. On a normal diet, we produce about 12 g of urea each day [ 2 ]. The bulk of the urea , about 10 g each day, is eliminated by the kidneys [ 2 ]. Being a diuretic, urea helps the kidneys quickly flush water and other compounds [ 4 , 5 ]. A small amount of urea less than 0.
During exercise , a substantial amount may be lost through sweat [ 2 ]. BUN levels represent the balance between [ 6 ]:. However, creatinine is a much more reliable marker of kidney function. BUN is far more likely to be affected by dietary and physiologic conditions unrelated to kidney function [ 2 ]. A BUN test measures the amount of urea nitrogen that's in your blood.
A BUN test can reveal whether your urea nitrogen levels are higher than normal, suggesting that your kidneys may not be working properly. If kidney problems are the main concern, the creatinine levels in your blood will likely also be measured when your blood is tested for urea nitrogen levels.
Creatinine is another waste product that healthy kidneys filter out of your body through urine. High levels of creatinine in your blood may be a sign of kidney damage. Your doctor may also test how well your kidneys are removing waste from the blood. To do this, you may have a blood sample taken to calculate your estimated glomerular filtration rate GFR.
The GFR estimates the percentage of kidney function you have. If your blood sample is being tested only for BUN , you can eat and drink normally before the test. If your blood sample will be used for additional tests, you may need to fast for a certain amount of time before the test.
Your doctor will give you specific instructions. During the BUN test, a member of your health care team takes a sample of blood by inserting a needle into a vein in your arm. The blood sample is sent to a lab for analysis.
You can return to your usual activities immediately. But normal ranges may vary, depending on the reference range used by the lab and your age. Ask your doctor to explain your results. Urea nitrogen levels tend to increase with age.
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