Normal levels. Normal levels of BUN are between 10 to 20 mg/dL for an adult and 5 to 18 mg/dL for a child. Normal creatinine levels are between .5 to 1.1 mg/dL for an adult female and .6 to 1.2 mg/dL for an adult male. Creatinine levels are lower in young children and the elderly as a result of reduced muscle mass.