When you bill an insurer that follows Medicare's "Eight-Hour Rule," you should assign observation care codes (99217, 99218-99234-99236) based on the following time and date criteria:
Keep in mind: If the patient stay for three or more days, then you should code the first day as observation discharge, and all the days in-between using outpatient established care codes (99211-99215).
Note: For Medicare's observation care guidelines, see page 2 of www.cms.hhs.gov/manuals/pm_trans/B0065.pdf.