- Anastomosis
- Anatomy
- Anatripsis
- Androgen
- Anemia, Cooley's
- Anemia, iron deficiency
- Anemia, Mediterranean
- Anemia, refractory
- Anencephaly
- Anesthesia
- Anesthetic
- Anesthetic, epidural
- Aneuploidy
- Angina trachealis
- Angioedema
- Angioedema, hereditary
- Angioid streaks
- Angiogram
- Angioneurotic edema, hereditary
- Angioplasty
- Angiotensin
- Angiotensin converting enzyme
- Anhidrosis
- Ankle-foot orthosis
- Ankle pain
- Ankylosing spondylitis
- Anomaly
- Anonymous reporting
- Anonymous testing definition - HIV: health and medical information about HIV and AIDS
- Anorexia
- Anorexia nervosa
- Anosmia
- Anoxia
- Anterior cruciate ligament
- Anthrax
- Anthrax immunization
- Antibiotic resistance
- Antibody, antinuclear
- Anticipation
- Anticoagulant agent