| Abbreviation | Definition |
|---|---|
| UN | Uranyl Nitrate |
| UNAV | Sodium Excretion rate |
| UNC | Uncertain |
| UNC | Unconscious |
| UND | UNDetermined |
| UNG | Ointment |
| UNK | Unknown |
| UO | Undetermined origin |
| UO | Urethral Orifice |
| UO | Urinary Output |
| UOD | Understanding Organ Donation |
| UOP | United Outstanding Physicians |
| UOP | Urine OutPut |
| UOQ | Upper Outer Quadrant |
| UPA | Urokinase Plasminogen Activator |
| UPCC | Utah Physicians Care Center |
| UPEC | Uro-Pathogenic Escherichia Coli |
| UPG | Unverified Personal Gnosis |
| UPIN | Unique Physician Identifier Number |
| UPJ | Uretero- Pelvic Junction |