I am 73 years old. my recent blood test results indicate bun of 29 and creatinine of .87. a bun/creatinine ratio of 33. i had not had anything to drink for around 13-14 hours before the test. is there a concern here with the high bun and ratio?

Your creatinine is in a good range (but always send normal values for you lab as the can differ between labs). Unless your body weight if very low. You need to have your Dr give you your eGFR as better measure of kidney function. Dehydration can increase the ratio sometimes. Discuss with your team.

All laboratory results need to be interpreted in the clinical context and the doctor who ordered the tests is usually in the best position to do that. Talk to the doctor who ordered the tests. Having said that, a high BUN/creatinine ratio in the face of a normal creatinine is usually and indication of dehydration. Drink enough water daily so that your urine is mostly colorless.