Universities need to be much clearer about whether they will contact parents if students have a mental health crisis, says a social mobility charity.
My Big Career, which helps poorer youngsters apply to university, says families being informed is a "lottery".
Following concerns over student suicides, some universities ask students if they want families to be contacted if there are serious worries.
But there is no requirement for universities to notify parents.
Right to confidentiality
Charity founder Deborah Streatfield says students and their families can be left unsure what will happen if there are mental health problems.
"Many are quite scared when a young person moves away from home for the first time," she said.
"If anything were to happen over the academic years, whether mental or physical illness, the university is under no obligation to inform anyone.
"It is a lottery for parents to know which universities have introduced this vital support."
In the wake of student suicides at the University of Bristol, the university introduced an "opt-in" system in which students can give consent for a parent, guardian or friend to be contacted if there are "serious concerns" about their well-being.
This year 93% of students at Bristol chose to opt-in to let family or friends be contacted - and there were 36 cases last year in which contacts were made, such as incidents of self-harm, concern about not being seen in halls of residence or deteriorations in mental health.
An inquest last year into the death of a University of Liverpool student, Ceara Thacker, heard that her family had not been informed about a previous suicide attempt three months before her death.
Students are adults and so have a right to confidentiality - which means universities have to ask if they will waive this privacy.
But for students currently making choices about university applications, there is no simple way to see which universities might have an arrangement for families to be contacted.
The higher education regulator, the Office for Students, says it does not keep a list of which universities offer such an option.
Admissions service Ucas does not have a list for students or parents of which universities offer such an opt-in for contacting families.
A spokesman says students are encouraged to declare any mental health conditions when they apply.
In last year's entry, there were almost 16,000 students who declared a mental health problem - a 19% increase on the previous year - and more than double the number in 2015.
The admissions service says when a student discloses a mental health condition, they will usually be contacted by a "trained individual" from the university to "discuss what support the student needs".
Universities UK is currently working on guidance to give to universities over contacting family - and says it has been consulting mental health and legal experts and students and parents.
The charity, My Big Career, is calling for all universities to offer an opt-in for parents.
But Universities UK says this has to be balanced against concerns that involving students' families could make matters worse.
The Department for Education says it has asked the university sector to consider how to better share information with students' families.
"Universities should work to improve how they involve family members in mental health support, while ensuring that students' best interests are central to any decisions about their care," said a department spokesman.