Students who transfer from one undergraduate college to another--or who transfer between multiple institutions--may hurt their medical school admissions chances. That's according to a September 2012 report from the Association of American Medical Colleges, which administers the MCAT.

Of the 31,479 M.D. applicants surveyed in 2011, students who went to only one college were admitted to medical school at a rate of 52.3 percent, compared with 35.6 percent for those who attended five or more institutions. The average MCAT score for students who attended one college was 29.1 (out of 45 points), while students who went to five or more schools scored 26.9 on average.

Among the respondents, 38.9 percent attended just one college, and 36.2 had two college transcripts, according to the report. Much smaller percentages of students attended three, four, or five or more schools: 16.6, 5.7, and 2.6 percent, respectively.

For the 61.1 percent of applicants who attended at least two colleges, the AAMC found that "multi-institutional attendance is associated with both lower mean MCAT exam scores and acceptance rates to medical school."

[For admissions tips, check out the Medical School Admissions Doctor blog.]

Although most references to transfer students on medical school websites are targeted at students wishing to switch from one medical school to another, some offer guidance for undergraduates.

Loyola University Chicago's Stritch School of Medicine, for instance, advises applicants to request at least one letter of recommendation from a faculty member at each school they attended. Barry University's School of Podiatric Medicine makes an exception for its dual MBA and doctor of pediatric medicine program and only applies its minimum 3.25 GPA requirement to transfer students' last 30 credit hours.

And Florida State University's College of Medicine cautions students not to split two-semester courses--such as organic chemistry I and II--between two colleges, although it doesn't explain why it offers that advice.

Ultimately, the AAMC study stresses that the number of undergraduate institutions that students attended was less important than the type of school, particularly given variations in resources, premedical educational programs, and other offerings.

[Check out the colleges with the most transfer students.]

Read more:

Study: College Transfer Students May Have Trouble Getting Into Med School