If you had prior commissioned service and are in HPSP or USUHS, you may be eligible for O-4 very early. Talk to your delailer and your intern advisor early on. You must request your records to be screened during internship by BUPERS due to being on active duty less than a year as a MC officer. I put on O-4, 6 months after finishing internship. One of my friends, who didn't think he had enough time in, would have been screened as a deep select, if he had requested a record review. That would have been an extra 4-5K this year for him!