- Cold, common
- Cold injury
- Colic
- Colitis
- Colitis, Crohn's
- Colitis, pseudomembranous
- Colitis, ulcerative
- Collagen
- Colon
- Colon cancer
- Colon cancer and polyps
- Colon cancer, family history of
- Colonoscope
- Colonoscopy
- Colony-stimulating factor
- Colorectal
- Colorectal cancer
- Colostomy
- Colostomy, a patient's perspective
- Colostrum
- Colpo-
- Colporrhaphy
- Colposcopy
- Colpotomy
- Coma
- Common bile duct
- Common cold
- Complementary DNA
- Complementary sequence
- Complete hysterectomy
- Compound microscope
- Compress
- Computed tomography
- Computerized axial tomography (CAT)
- Concussion
- Conditioning, Pavlovian
- Condyloma acuminatum
- Congenital clasped thumb with mental retardation
- Congenital defect
- Congenital heart disease