- Ulcerative colitis (large intestine inflammation)
- Umbilical hernia (belly button hernia)
- Unisom overdose (doxylamine overdose)
- Unstable angina (pre heart attack chest pain)
- Upper respiratory tract infection (URI, common cold)
- Ureaplasma urealyticum infection (genital infection)
- Urethral stricture
- Urethritis (infection of urethra)
- Urinary tract malformation
- Urine retention (inability to urinate)
- Urticaria (hives)
- Uterine cancer
- Uterine prolapse (uterine vaginal protrusion)
- Uterine rupture (uterine tear during childbirth)
- Uveitis (iritis, eye inflammation)