The Wolfson Medical Library at Glasgow University is to have its opening hours reduced from 168 a week to 60.
Students will have access only from 8am to 8pm during week days instead of the 24-hour access currently offered.
The student union say it is essential medical students are offered access at all hours of the day because of the shift work they do in hospitals as part of their training.
However, Glasgow University said it was acting on concerns raised by students about the behaviour of other students during unsupervised periods in the library.
It is to extend the library hours that are supervised from 8am to 8pm. A spokesman said the main library would remain open until 2am.
The university's plans are due to be implemented at the start of the new semester next month.
James Harrison, president of the Students' Representative Council, said: "The student experience at the university will be damaged if these proposals go ahead.
"We call on the university to rethink its plans and stop this drastic reduction in hours."
A spokesman for the university said: "We are committed to engaging with students on these proposals and have invited representatives of the SRC to a meeting that will be held later this month to discuss the best way ahead for all."