Diagnosaurus
- Idiopathic pulmonary fibrosis
- Idiopathic thrombocytopenic purpura
- Id reaction
- IgA deficiency, selective
- IgA nephropathy
- Ileus, acute paralytic
- Immunodeficiency, common variable
- Immunodeficiency disorders in adults
- Impetigo
- Impotence
- Incontinence, fecal
- Incontinence, urinary
- Infectious mononucleosis
- Infective endocarditis
- Infertility, male
- Inflammatory bowel disease
- Inflammatory bowel disease–associated arthritis
- Influenza
- Insomnia
- Interstitial cystitis
- Interstitial lung disease
- Interstitial nephritis
- Intertrigo
- Intestinal ischemia, acute
- Intestinal ischemia, chronic
- Intestinal obstruction, large
- Intestinal obstruction, small
- IPF
- Iritis
- Iron-deficiency anemia
- Iron poisoning
- Irritable bowel syndrome
- Ischemic bowel, acute
- Ischemic bowel, chronic
- Ischemic colitis
- Isoniazid (INH) poisoning
- Isosporiasis
- ITP