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Hello from JustAnswer.
A BUN level of 9 would typically not be the cause of tiredness and nausea. It is true that kidney disease can cause these symptoms, but the BUN would typically be elevated in that situation. Liver disease or gallbladder disease will frequently cause nausea or tiredness, but the BUN is not a test to assess for liver or gallbladder disease.
There are many other conditions that can cause tiredness and nausea.
So, the answer to your direct question is that the low BUN would typically not be the cause, but the question of whether liver disease could be causing the symptoms is not addressed with this information.
Were there any liver blood tests done at the same time as the BUN, such as AST, ALT, bilirubin, or alkaline phosphatase?
Has there been any other evaluation done for these symptoms?
First, this level of BUN is close enough to the normal range that it is likely normal, not low. About 2.5% of normal people will have a result that is only slightly below the normal range, and these people are normal. However, even with a truly low BUN, it is usually not a concern. The BUN can be low with any condition that causes fluid retention, including liver disease, but in the vast majority of cases, a low BUN is not a concern. If the BUN is truly low and tests of the liver is normal, then there is no reason to be concerned about liver disease.
We typically only use the liver blood tests to assess liver function, such as AST, ALT, bilirubin, or alkaline phosphatase. Since the bilirubin and alkaine phosphatase was checked, the others were probably also checked, but may have been labeled differently, such as aspartate transaminase or SGOT instead of the the AST or alanine transaminase or SGPT instead of ALT.
Can you find the tests using these other names?
Very good. All of the liver tests are normal, so there is no reason to be concerned about liver dysfunction. The blood tests, though, are not a full assessment for gallbladder disease. An ultrasound of the gallbladder and liver would be the usual test that would look for gallbladder disease.
Is there any other information that would be helpful?
The alkaline phosphatase can reflect liver disease, but since the other liver tests are normal, it is usually not from liver disease. It can still be elevated from conditions that affect the bile drainage from the liver, such as gallbladder disease, which is why checking the ultrasound of the gallbladder would be appropriate. The alkaline phosphatase can also be elevated from any condition that affects the bone, so if the gallbladder is normal, it would be appropriate to consider evaluation for bone disease.
Please let me know if I can provide any additional information.