There is no right answer to this question because each situation is different. If you are a senior and you have a 2.5 GPA, it would be wise to consider other career options. However, if you are a freshman or sophomore and you have a 3.0-3.5 GPA, there is still hope (the higher the GPA, the greater the hope). If you are a first year student, do not be discouraged by one bad semester or quarter.
To receive an answer more specific to your situation, you can discuss your situation with a career or pre-med counselor, mentor, or other experienced pre-meds.