42 CFR §422.568(b)(1)

(b) Timeframes – (1) Requests for service or item. Except as provided in paragraph (b)(1)(i) of this section, when a party has made a request for a service or an item, the MA organization must notify the enrollee of its determination as expeditiously as the enrollee’s health condition requires, but no later than 14 calendar days after the date the organization receives the request for a standard organization determination. (i) Extensions; requests for service or item. The MA organization may extend the timeframe by up to 14 calendar days if – (A) The enrollee requests the extension; (B) The extension is justified and in the enrollee’s interest due to the need for additional medical evidence from a noncontract provider that may change an MA organization’s decision to deny an item or service; or (C) The extension is justified due to extraordinary, exigent, or other non-routine circumstances and is in the enrollee’s interest. (ii) Notice of extension. When the MA organization extends the timeframe, it must notify the enrollee in writing of the reasons for the delay, and inform the enrollee of the right to file an expedited grievance if he or she disagrees with the MA organization’s decision to grant an extension. The MA organization must notify the enrollee of its determination as expeditiously as the enrollee’s health condition requires, but no later than upon expiration of the extension.