Three main rules govern observation coding:
1. Report 99218-99220 with 99217 if the physician admits the patient to observation and releases her on a different date of service, unless the total duration of observation stay equals fewer than eight hours. For stays lasting multiple days, you may report one unit of 99218-99220 for each date of service (not counting the date on which the physician discharges the patient).
2. For stays of less than eight hours when the admission and discharge occur on different dates of service, report only 99218-99220 (Initial observation care, per day, for the evaluation and management of a patient).
3. For observation stays that take place within a single date of service, you should report the observation/inpatient hospital care E/M codes 99234-99236 (Observation or inpatient hospital care, for the evaluation and management of a patient including admission and discharge on the same date). You should not report a separate discharge code with 99234-99236.
In your case, the patient observation stay spans two dates of service but lasts only four hours total. Therefore, you should choose just the appropriate-level initial observation care code (99218-99220).
If the observation care had spanned two dates of service with a total duration of more than eight hours (for instance, the gastroenterologist admits the patient at 9 p.m. and discharges her the next day at 9 a.m.) you could report both the initial observation care (99218-99220) and the discharge service (99217, Observation care discharge day management).
In a third scenario, the gastroenterologist admits the patient at 9 p.m. on Thursday and does not discharge the patient until 9 a.m. on Saturday. In this example, you may report one unit of 99218-99220 for Thursday, one unit of 99218-99220 for Friday, and the discharge (99217) on Saturday.
Finally, consider the case in which the physician admits a patient at 6:00 a.m. and discharges her that day at 8 p.m. Because the admission and discharge occur on the same date, you should report 99234-99236 only.
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If the patient is in observation status in the hospital both days, admitted to observation by someone else, and you are asked to consult the first day and then you followed on your own the second day.
If this is a non-Medicare patient, the consult the first day is coded 99241-99245, and the visit the next day is coded 99224-99226.
If the patient has Medicare, then day one is coded 99201-99205 or 99211-99215, depending on whether you have seen this patient before, and day two is coded 99224-99226.