- Labial fusion
- Labour
- Labyrinthitis
- Lacerations
- Lactose intolerance
- Laparoscopic cholecystectomy
- Laparoscopy
- Laryngeal (larynx) cancer
- Laryngitis
- Laryngotracheitis
- Lateral epicondylitis
- Laxatives
- Lazy eye
- LDH
- Leg cramps
- Leg ulcer, venous
- Legionnaires' disease
- Leptospirosis
- Leukaemia, acute lymphoblastic
- Leukaemia, acute myeloid (AML) in adults
- Leukaemia, acute promyelocytic
- Leukaemia, chronic lymphocytic
- Leukaemia, chronic myeloid
- Leukaemia, chronic myelomonocytic
- Leukaemia, hairy cell
- Leukaemia, large granular lymphocytic
- Leukoplakia
- Lice (head)
- Lice (pubic)
- Lichen planus
- Lightheadedness
- Lipid-lowering medicines
- Lipoedema
- Lipoma
- Liposuction
- Lips, sore or dry
- Listeriosis
- Liver cancer