Not all people reach their dreams with the same ease. As a possible reapplicant, how can I get a sense of what my chances for success are? First you need to answer these questions:

1. Have I made myself stronger than I was last time? Take stock and see if your grades are improving, and if your health related experience and/or research is getting better.
2. Have I remedied or explained any weaknesses that I have? (Not always the same as question 1). Sometimes, an application has one main weakness: a low score on an MCAT section, a bad grade in an important prerequisite, or lack of health-related experience or research. Have I completely made up for my weakness?
3. Am I less picky than I was last year? Imagine that a student came up to you who applied only to Harvard and Columbia last year, just those two schools and nothing else. If that student then tells you that he or she was rejected, you would probably tell them to apply to a broader range of schools next time!

Overall, the best time to reapply is when you have made yourself considerably stronger. Sometimes, this might mean waiting a year before reapplying, but for the person who is serious about their goals it is time well-spent.