You are obliged to be properly insured during your time abroad. Next to being obliged, you also don’t want to be surprised by having to pay for unforeseen medical issues.
Students coming from EU member countries and the countries of the European economic region should have European Health Insurance Card which can be used to cover any necessary medical treatment due to either an accident or illness within the EEA - European Economic Area (E 128 form, E 111 form or E-card. The document type depends on the authorized insurance agency of the country of their origin).
If your stay will exceed a period of three months, a residential permit is required.