This article is from the Medical Education FAQ, by email@example.com (Eric P. Wilkinson, M.D.)with numerous contributions by others.
If you received greater than 27 on your first attempt, it is
advisable to apply with your current score and not take the test
again. If you received less than 24, you should probably take the
test again, prepare harder next time, and try to improve your score.
The range of 24-27 is a grey zone: whether to take the test again
depends on the rest of your application and on where you are
applying. Note that these are just guidelines. You must consider
your own individual situation to arrive at a final decision. Also
note: if you take the MCAT in April and are dissatisfied with your
scores, you can go ahead an apply anyway and still retake the test
in August for the same application year. It's better to submit your
application early than to submit it in the fall.