ANSWER: Yes, in most cases. If OPM denies your application, they will do so in an initial decision, and you can request that they reconsider that decision. But be aware that in some cases, OPM may randomly toss your case into its new experimental "pilot project," and not give you another opportunity for review. If this happens, the only way to win disability retirement is to appeal to the MSPB and start all over again there. I will discus this "pilot project" in more detail below.
Most applications that are denied are first issued an initial decision. If this happens to you, you will be given the opportunity for reconsideration. Your reconsideration request must be received by OPM within 30 days of the date on your initial decision letter. You will also have to submit additional documentation or information in response to OPM's initial adverse determination. If you are unable to provide the information within the 30 day time limit, be sure to request reconsideration and an extension of the time limit so you can provide that additional information. If your request for additional time is received within the 30 day time limit, it will almost certainly be approved, although OPM does have the power to deny it.