Is it possible to have high creatinine, high blood urea nitrogen and high potassium levels simultaneously?

Yes: High creatinine and BUN occur in poor kidney function. High potassium levels can occur when kidney function is poor because kidney cannot get rid of potassium.

Absolutely yes: This is exactly what is seen with kidney (renal) failure. I am not making a diagnosis on this information alone. I can only advise strongly that anyone with elevation in bun, cr and potassium, as listed above, should see his/her physician immediately.