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What could be the cause for elevated blood urea nitrogen levels?

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General & Family Physician
Practicing since : 2001
Answered : 8456 Questions
I am a 55 y/o female. In the last 2-1/2 months I have been following a low carb diet. In addition to changing my diet, I started a good exercise program too. Every morning M-F I do a 30 minute interval training (Jillian Michaels shred routine). In addition to that I try to get in another 2-3 days of a 30-60 min cardio routine. I had a blood draw done a couple of weeks ago and it included CBC, CHEM, Thyroid, and Lipid profile. On the day of the lab draw I had fasted overnight and I did do my morning workout. My BUN results were elevated at 21. The end of the normal range was 17. My BUN/Creat ratio was 22:1. I did send the results to my physician and his nurse said there were no concerns about that test. The creatinine was in normal range at 0.95. Please help me understand why the results were elevated.
Posted Thu, 6 Feb 2014 in Kidney Conditions
Answered by Dr. Michelle Gibson James 28 minutes later
Brief Answer: related to diet changes Detailed Answer: HI, thanks for using healthcare magic Blood urea nitrogen (BUN) reference range can vary slightly from one lab to the next. Urea is made in the liver and excreted by the kidneys. There are situations that can cause slight increase in BUN levels without indicating that there is any significant problem for example increased protein intake. The rate of urea (BUN ) production is not constant. It is increased in persons who use an increased amount of protein and also in situations where there is increased breakdown of tissue (hemorrhage, trauma , steroid therapy). Some antibiotics can also increase levels. It is likely that the slight increase you are noticing is related to your low carb diet. The increased protein intake would cause increased urea levels. It is not indicate you have any kidney disease and you can continue with your lifestyle changes. Good luck and God bless. Please feel free to ask any other questions
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Follow-up: What could be the cause for elevated blood urea nitrogen levels? 3 hours later
I forgot to add one test result that was also elevated. It was the ALP. Mine was 100 and the upper part of range was 92. My ALT was low at 4 and my AST was 15 (I hope I do not have those backwards). I had very sore muscles and my calves had been really hurting from some exercises. Not sure if that could affect the ALP. Again, my doctor was not concerned. I did not know if the BUN and ALP being high at the same time could have meaning. Those are the only tests results, other than LDL, that were out of range. I completely understand the LIPIDS, so I do not have any questions about that test. Thank you so much for explaining these to me.
Answered by Dr. Michelle Gibson James 6 hours later
Brief Answer: increased alp may be due to increased bone mass Detailed Answer: Hi, sorry about the late reply, Alp (alkaline phosphatase) is released from the liver, bone , kidneys, intestines. Again the upper limit can vary from lab to lab but on average the limit is approximately 100. Even though your value is above your labs upper limit, it is not significantly so. The increase in alp may reflect increase bone mass due to your exercise. This increase can occur in some persons as a result of exercise. Increased bone mass is good because it decreases the risk of fracture as aging occurs. When using the lab units u/l, normal ast range is approximately 10 to 36 and alt 7 to 35. Your lab ranges may vary slightly from this. The ast would be in range though the alt would be low. Usually alt is significant if it is increased , that usually indicates liver disease. Your value, though below the normal range, is unlikely to indicate any significant pathology since there are no other significant changes in the other tests. Please feel free to contact with any other questions
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