I am 49 year old male in good general. A recent blood test showed bun level at 27 and creatinine level at 1.4. Should I be concerned? What are possible causes?

Dehydration? Sounds like dehydration (if no kidney disease) as we grow younger, we cannot rely on our thirst, and have to drink by the clock... Our osmotic receptors get old before we do.
Needs work up. The cr is high, there are many causes and you need further work up, the most common causes are prolonged diabetes and high blood pressure. Make sure that you get follow up with your physician.