For the first time in 25 years of continuous crewed operations, an astronaut has been medically evacuated from the International Space Station (ISS). The Crew-11 mission ended when a SpaceX Dragon capsule brought the four astronauts of Crew 11 home following a medical incident in early January 2026.

To protect the crewmember’s privacy, Nasa hasn’t yet disclosed details about what happened – and this article won’t speculate. But the evacuation raises a question worth exploring: how do astronauts stay healthy in space, and why is this early evacuation so unusual?

Astronauts undergo rigorous medical screening before selection. They are assessed for conditions that might worsen in microgravity, evaluated for psychological resilience, and monitored throughout their careers.

Although modelling suggests a medical emergency could be expected roughly every three years on the ISS, serious issues are remarkably rare in practice.

Every ISS mission includes medical support both in space and on the ground. Each crew has a designated Crew Medical Officer – sometimes a qualified doctor, sometimes someone with extensive training in space medicine procedures. They can perform basic examinations, administer medications, and conduct telemedicine consultations with specialists on Earth.

A 2015 study found that medication use on the ISS was relatively low, with roughly ten doses........

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