Insurance
Krankenkasse (TK, AOK & co.)
A Krankenkasse is a statutory health-insurance fund. TK, AOK, Barmer, and DAK are the biggest names. Benefits are 95% identical by law; funds differ in supplementary rate, English-language service, app quality, and bonus programs, and students can switch with notice.
Krankenkassen are the self-governing public funds that operate statutory health insurance. Around 90 funds exist, from nationwide giants like Techniker Krankenkasse (TK), AOK, Barmer, and DAK to regional and company-linked funds. The benefit catalog is fixed by law, so medical coverage barely differs; competition happens through the supplementary contribution rate (Zusatzbeitrag), service quality, digital tools, and extras like dental cleaning subsidies or sports bonuses.
Every fund must accept every applicant regardless of health status. Switching is allowed after 12 months of membership, or immediately when your fund raises its supplementary rate, with the switch handled mostly by the new Kasse.
What it means for working students
For international students the practically relevant differences are English-speaking hotlines and document support: TK is the default recommendation in most international-student communities for exactly that reason, with Barmer and DAK close behind. The price spread between funds at the student rate is a few euros per month, so optimize for service, fast issuance of enrollment certificates (your university and employer will want them), and an app you can actually navigate.