Historically, the medical criteria for astronaut selection have been kept extremely classified. But recently, NASA decided to make its astronaut medical standards for selection and annual recertification publicly available.  NASA is considered a global leader in human spaceflight, so while some differences may exist between agencies, variations are likely minimal.  So NASA's publicized standards offer the most transparent insight into the medical requirements of astronaut selection.

This article provides a brief summary of each of the types of testing and includes a list of the specific tests mentioned in the standards.

⚠️ Disclaimer: This article is tailored for readers with a keen interest in the intricate medical facets of astronaut selection. For most applicants, a general overview of the medical process is adequate. This piece does not provide medical advice or recommendations. Concerns about one's health should be addressed by consulting a healthcare expert. Please refrain from reaching out to Astro Perform for specific inquiries about medical selection.


A thorough inspection of the eyes is conducted, which encompasses a standard eye test where individuals read letters from a wall chart. Specialized visualization techniques are also used to closely examine different parts of the eye.

  • Visual acuity (Snellen or Landolt-C)
  • Near vision
  • Color vision (computer-based test, Ishihara, or equivalent pseudo-isochromatic plates [PIPs] covering red-green and blue-yellow)
  • Cycloplegic refraction
  • Phorias
  • Tonometry
  • Perimetry
  • Fundoscopic examination
  • Retinal photographs
  • Corneal topography


Tests include hearing assessments, how the eardrum responds to air pressure in the ear canal, and imaging techniques to observe air-filled spaces in the face (sinuses). An in-depth dental analysis is also conducted.

  • Audiometry (pure tone audiogram and, if needed, speech audiogram)
  • Tympanogram
  • CT or MRI scans of sinuses
  • Special Assessment by Dentist
  • Full orthopantomogram or complete mouth X-ray series


The cardiovascular system is thoroughly investigated. Examinations focus on the lungs and heart both individually and collectively, especially during intense physical tests. A specific test observes arterial calcification—a predictor of future heart attacks.

  • Resting 12-lead ECG
  • Direct or indirect cardiorespiratory fitness measurement during a maximum exercise stress test
  • Echocardiogram with Doppler and color flow study
  • 24-Hour ECG monitoring
  • Pulmonary function testing
  • Cardiovascular Risk Prediction
  • Coronary calcium scoring


The primary test here examines the colon. A laxative is administered beforehand to ensure an empty colon, and a flexible tube with a camera is inserted for the procedure.

  • Colonoscopy


Assessments encompass brain structure and behavioral function. Imaging captures multiple brain views to identify potential issues, such as indications of future strokes. Psychological evaluations focus on behavioral and emotional functions, personality traits, cognitive processes, and overall suitability for spaceflight challenges.

  • MRI of the brain and MRI angiogram
  • Carotid Ultrasound Study
  • Psychodiagnostic Assessment based on the most recent Diagnostic and Statistical Manual of Mental Disorders
  • Psychological Suitability Assessment


This section assesses cervical health and, for those over 40, breast health. Both evaluations help identify early cancer signs.

  • Gynecological Evaluation
  • Breast Imaging for females starting at age 40


Advanced imaging captures detailed views of the chest, neck, abdomen, and hips. A whole-body scan evaluates bone density. Due to spaceflight radiation risks, a comprehensive radiation exposure history is also collected.

  • Chest X-ray (PA and lateral)
  • Thyroid ultrasound
  • Abdominal and pelvic ultrasound
  • Bone mineral density via DXA scan
  • Radiation History Assessment


Blood samples undergo laboratory analysis. The extraction process involves inserting a needle into a vein near the elbow.

Blood disorders / clots:

  • Complete Blood Count
  • Reticulocyte count
  • Screening tests for thrombophilia
  • Hemoglobin evaluation

Biological processes:

  • Liver function tests
  • Total serum protein, albumin
  • Renal function tests
  • Endocrine tests
  • Fasting blood glucose, HbA1C
  • Cardiovascular profile
  • Mineral levels

Infectious diseases:

  • Serologic screen for syphilis
  • Hepatitis B and C tests
  • HIV
  • Tuberculosis screening

Special studies:

  • Prolactin
  • Carbohydrate Deficient Transferrin
  • Ethyl glucuronide
  • Tissue transglutaminase tests


A urine sample will be requested, typically collected in a cup or tube.


  • General urine tests like specific gravity, glucose, etc.
  • Microscopic examination

Women’s Health:

  • Human chorionic gonadotropin (hCG) test

Drug screening:

  • In-house drug screening
  • Expanded drug screening