42 C.F.R. § 21.34
If a candidate for appointment in the Regular Corps or an officer of the Reserve Corps on inactive service has passed a physical examination within a period of one year from the date on which it is contemplated that he will be appointed or called to active duty, he shall, prior to being appointed or called to active duty, certify that to the best of his knowledge and belief he is free from all disease or injury not noted in his record at the time of his examination and that he is willing to serve in any climate. If a candidate for appointment in the Regular Corps, or an officer of the Reserve Corps on inactive service, has not passed a physical examination within a period of one year from the date on which it is contemplated that he will be appointed or called to active duty, he may, prior to being appointed or called to active duty, be required to undergo such physical examination as the Surgeon General may direct to determine his physical qualification for appointment or call to active duty in accordance with standards prescribed for original appointment, or he may be appointed or called to active duty after executing the certificate described in this section, but shall be physically examined to determine his physical qualification for continued active service in accordance with standards prescribed for original appointment within a period of 15 days after reporting for duty at his first station.
Provisions Applicable Only to Regular Corps
42 C.F.R. §21.34