Many US universities require International students to have a mandatory health insurance, which is a good thing. Because medical care is not free in United States and in the event of an accident or emergency if the international student doesn’t have a health insurance the bills will sky rocket. It’s best to buy the medical insurance provided by the participating university since its much cheaper.
Although there are no federal insurance requirements for F1- Visa students, individual universities will handle the requirements pertaining to the admitted students. It is prudent to check the respective school website for health insurance requirements as it might vary
Some schools may vary mandatory health insurance of the student purchases an international health insurance. To check if the international insurance is adequate check the respective school waiver requirements for health insurance
Some of the common insurance requirements are coverage for mental health, maternity, pre-existing condition, emergency etc. and adequate policy maximum may vary for participating schools.
During Optional Practical Training period and after graduation, they are no longer have to purchase a plan compliant with their college or university requirements, and have the freedom to purchase any insurance plan the students would like.
If the students got a H1-B sponsorship, then the respective employer will provide health insurance either for free, including individuals on their OPT (not always the case)