My BUN was above the range early in my LCish Paleo diet, but my doctor was unconcerned and didn't even bother to mention it. Did your physician mention it? It's reportedly a pretty common lab result for LCers, especially early on in the diet, apparently, and is widely reported as a benign phenomenon. Here are some posts on the topic:

Elevated BUN levels?
http://www.lowcarbfriends.com/bbs/general-health-medical-issues/761049-elevated-bun-levels.html

creseis
"... Volek and Phinney point out that high uric acid concentrations will occur in the beginning phase of low carb due to competition with ketones for renal tubular excretion (so ketones are excreted and uric acid remains in the blood and will temporarily cause increased levels of uric acid in the blood), which will give the appearance of high uric acid concentrations, but it is really innocuous. If you go off plan/out of ketosis at all during this period, this situation will be reinstated."

brandywine12
"I also have elevated bun on this last lab work up. It seemed it went a tad up almost every time I was to get it checked with regular lab work. I figured it had to do w/the amount of protein I was eating. I have been into it for a year and 1 month. I was eating a lot of protein from july until jan , I had these labs due and my dr was putting me on statins so i stopped eating a lot of fatty foods. So I figured it was because of that. My range is 7-17 , mine was 18. My dr didn't seem to concerned."


Why You Neet to Get Copies of Your Lab Test Results
December 6, 2010
Jenny Ruhl
http://diabetesupdate.blogspot.com/2010/12/why-you-neet-to-get-copies-of-your-lab.html

"When you get your lab tests you will often see values flagged as high that your doctor has not mentioned. The most common of these is the BUN which is often elevated in people who are eating a low carb diet because the low carb diet induces a degree of dehydration that affects the test result but does not cause any health problems. If you see a value on your lab sheet that concerns you, ask your doctor about it."


>On Apr 4, 2012, at 6:07 PM, Sandy Rzetelny  wrote:
>
>> Hi
>> I have been doing low carb sort of paleo for the  last 6 months. My
>recent
>> blood test showed that the  bun/creatinine  ratio was 29 whereas
>reference
>> range is  6-25.
>>
>> Any thoughts thoughts about this?
>>  Thanks
>> Sandy
>
>
>