Anemia is a lack of red blood cells (RBCs) in the circulation. Because RBCs carry the oxygen your body needs to function, anemia can affect one's ability to stay awake, alert, and perform physical activities. Anemia may happen for several reasons, including increased RBC destruction. Anemia often occurs in people who have been in bed for long periods (e.g., if they are very sick) or have decreased mobility (anemia of immobility). Interestingly, astronauts who have left Earth and traveled in space also return anemic. In fact, 5 decades of NASA data showed that astronauts' anemia was more severe the longer they were in space. In another study, astronauts aboard the International Space Station were shown to destroy 54% more of their RBCs in space. RBC destruction may be the culprit of space anemia as well as anemia of immobility on Earth. The ANEMIA Study proposes to measure key aspects of RBC destruction in astronauts in space. These measures will test critical hypotheses on the effects of spaceflight on red blood cells.

Inclusion Criteria:

• Astronauts selected to fly on a space mission.

Exclusion Criteria:

• Astronauts not selected to fly on a space mission.

Astronauts selected to fly on a space mission.

There may be multiauthor publication involving multiple PI on the same astronauts for this mission. Each PI contributing to the manuscript their individual data.