This Hot Takes article is an editorial explainer based on public NASA documents and spaceflight research. It is not medical advice, it is not a diagnostic guide, and it has not been medically reviewed.
Astronaut Scott Kelly spent a year in space while his identical twin brother, Mark Kelly, stayed on Earth. Over that period, researchers collected biological data from both men to study what long-duration spaceflight does to the human body.
That project, the NASA Twins Study, became one of the best-known examples of astronaut biomarker research. It looked at gene expression, immune response, cognition, the microbiome, and biochemical changes.
But it also raises a simpler question: what blood tests do astronauts actually get?
The public answer is incomplete, because NASA does not publish every operational medical detail for every mission. But NASA standards, former-astronaut examination requirements, Human Research Program materials, and peer-reviewed spaceflight studies reveal a lot. The short version: NASA tracks many of the same broad lab categories used in ordinary clinical medicine, then layers on mission-specific monitoring for radiation, microgravity, bone loss, immune changes, vision changes, and other spaceflight-specific risks.
Why NASA monitors astronauts so closely
Astronaut medical testing is not wellness optimization. It is occupational health for a tiny group of people exposed to conditions almost nobody on Earth experiences.
NASA's Lifetime Surveillance of Astronaut Health program, or LSAH, screens and monitors astronauts for occupationally related injury or disease. The program analyzes health risks linked to astronaut occupational exposures.
The governing framework sits in NASA-STD-3001, Volume 1: Crew Health. NASA describes this standard as establishing crew-health technical requirements for the pre-mission, in-mission, and post-mission phases of human spaceflight.
That matters because astronauts face a different risk stack from ordinary patients:
Microgravity changes bone, muscle, cardiovascular function, fluid distribution, and vision. Space radiation creates a lifetime exposure problem, not just a single-mission problem. The International Space Station is medically remote, even though it is in low Earth orbit. A Mars mission would be much more isolated, with far less ability to return a sick crewmember quickly. * Biological samples collected in orbit may be frozen and analyzed later, not processed like a normal outpatient lab draw.
NASA's radiation standard is a good example of the occupational framing. NASA-STD-3001 Revision C sets a career space permissible exposure limit for spaceflight radiation of less than 600 mSv total career effective dose. That is not something a normal annual physical has to manage.
The public bloodwork list: what NASA says former astronauts get annually
The clearest public list of NASA astronaut lab testing appears in NASA's Medical Examination Requirements for Former Astronauts. This is not necessarily the full active-flight protocol, but it is an unusually specific public window into the categories NASA tracks through lifetime surveillance.
NASA's former-astronaut annual laboratory testing includes the following:
Complete blood count (CBC) Biochemistry Fasting glucose and A1c Lipids High-sensitivity CRP (hs-CRP) Calcium, magnesium, and phosphate Prostate-specific antigen (PSA) for males beginning at age 50 Iron studies
That list is striking because most of it is not exotic. It overlaps heavily with routine outpatient laboratory medicine.
The spaceflight context is what makes it unusual. NASA is not asking, "what would a curious consumer like to know?" NASA is asking, "what does this crewmember's body look like before and after exposure to microgravity, radiation, operational stress, altered sleep, confined habitat conditions, and mission-specific workload?"
Before flight: establishing the baseline
Before a mission, the key job of testing is to establish baseline health. NASA's Spaceflight Standard Measures project collects blood and urine chemistry, immune markers, microbiome, sleep, cognition, cardiovascular, sensorimotor, and team-process measures around ISS missions.
NASA needs to know what is normal for a specific astronaut before launch. Without that baseline, it is harder to interpret changes after weeks or months in orbit.
During flight: collecting samples is easier than running a full lab
One of the counterintuitive facts about astronaut blood testing is that drawing blood in orbit does not mean NASA can run a full hospital-style lab panel in orbit.
NASA has publicly described a major limitation: current ISS venous blood draws are collected, frozen, and analyzed after return to Earth for research purposes. NASA notes that in-space white blood cell counting was a missing capability being evaluated.
So in-flight monitoring relies heavily on research sample collection, where samples are stored and returned for later analysis. NASA's Research Operations and Integration group supports ISS collection of blood, urine, fecal, skin microbiota, and saliva samples. They provide hardware, such as centrifuges, for sample collection.
This is a crucial distinction. In ordinary consumer lab testing, the blood draw and analysis happen within the terrestrial lab system. In orbit, sample handling is part of the mission architecture.
What the NASA Twins Study added
The NASA Twins Study was not a routine physical. It was a research study comparing Scott Kelly during a year in space with Mark Kelly on Earth.
The study reported spaceflight-associated changes including telomere elongation, altered gene expression, carotid changes, ocular structure changes, microbiome changes, and postflight cognitive changes.
The important editorial point is not that every astronaut now gets a "Twins Study panel." They do not. The point is that astronaut research has shown why NASA cares about broad biological monitoring: spaceflight affects multiple systems at once.
After flight: recovery is a monitoring problem
Landing is not the end of the physiology story.
After return to Earth, astronauts have to readapt to gravity. Bone is one of the clearest examples. NASA states that weight-bearing bones can lose about 1% to 1.5% of density per month during four-to-six-month missions. Astronauts undergo routine bone scans before and after spaceflight to monitor these changes.
Vision is another major focus (pardon the pun.) Spaceflight Associated Neuro-ocular Syndrome (SANS) involves optic nerve swelling, retinal folds, posterior globe flattening, and related eye and brain changes during spaceflight.
Not all of this is bloodwork. DXA scans, ultrasound, ocular imaging, and other non-blood measurements matter. But blood and urine markers provide one part of the recovery picture, especially for inflammation, immune function, bone turnover, kidney function, liver function, endocrine status, and general chemistry.
How ordinary lab tests overlap with astronaut monitoring
The overlap between NASA's public lab categories and ordinary clinical testing is real, but it should not be overread. A consumer can order many tests that resemble the categories NASA monitors. That does not make the consumer an astronaut, and it does not make the interpretation equivalent.
Here is the clean way to think about it:
| NASA monitoring category | Ordinary lab-test analogue | Lab Test Details |
|---|---|---|
| Hematology | Complete Blood Count | CBC |
| General chemistry | Comprehensive Metabolic Panel | CMP |
| Glucose regulation | Fasting glucose, A1c, fasting insulin | Glucose, A1C, Insulin, Diabetes Risk Panel |
| Lipids | Cholesterol and triglycerides | Comprehensive Lipid Panel |
| Thyroid | TSH and free T4 | Thyroid Function Panel |
| Bone and mineral context | Calcium, magnesium, phosphate, vitamin D | Vitamin D Test, CMP |
| Iron status | Iron, TIBC, transferrin saturation, ferritin | Iron Panel |
| Inflammation | hs-CRP | High-Sensitivity CRP |
| Stress and hormone context | Cortisol, testosterone and other hormones when clinically relevant | Cortisol AM, Testosterone Free and Total |
| Age and sex-specific screening | PSA for males beginning at age 50 | PSA Test |
The tests may overlap. The purpose does not. NASA is monitoring a small occupational cohort with unusual exposure history. Ordinary outpatient labs are interpreted in the context of ordinary clinical care, symptoms, risk factors, medications, personal history, and clinician judgment.
What NASA tests that ordinary consumers generally cannot copy
The astronaut monitoring stack includes things that are not equivalent to a consumer blood panel:
Individual radiation dosimetry and career exposure tracking Mission-specific medical standards Specialized immune and cytokine research panels Spaceflight sample collection and storage protocols In-flight ultrasound and ocular imaging Bone-density monitoring tied to microgravity exposure Multimodal research protocols such as the Twins Study Operational flight-surgeon oversight
This is where the phrase "astronaut blood panel" can become misleading. There is no simple public consumer equivalent of NASA's astronaut medical program. NASA's approach is a system, not a shopping cart.
The real takeaway
The most interesting thing about astronaut bloodwork is not that NASA uses mysterious biomarkers. It is that NASA uses ordinary biomarker categories inside an extraordinary operating environment.
A complete blood count is still a complete blood count. A fasting glucose test is still a fasting glucose test. A lipid panel is still a lipid panel. But in NASA's hands, those results become part of a longitudinal occupational-health record that has to account for microgravity, radiation, fluid shifts, altered sleep, immune changes, bone loss, mission stress, and return-to-gravity recovery.
That is the useful lesson for the rest of us: context is everything. Blood tests are not magic answers by themselves. They become useful when they are tied to a clear question, a reliable baseline, and a careful interpretation framework.
NASA has one of the strangest and most demanding interpretation frameworks on Earth, and just above it.