List of medical abbreviations: U
# List of medical abbreviations: U

| Abbreviation | Meaning |
| - | - |
| $U_{OSM}$ | urine osmolality |
| UA | urinalysis unstable angina |
| U/A | upon arrival |
| UAE | Uterine Artery Embolization (synonym for Uterine Fibroid Embolization) |
| UBT | urea breath test |
| UC | ulcerative colitis uterine contraction |
| UCHD | usual childhood diseases (see list of childhood diseases) |
| UCTD | Undifferentiated connective tissue disease |
| UCx | Urine culture |
| UD | as directed (from Latin ut dictum) |
| UDS | urine drug screening Undifferentiated sarcoma |
| UDT | urine drug test undescended testis |
| UE | upper extremity |
| U&E | urea and electrolytes (blood test) (for sodium and potassium, and often creatinine) |
| UFE | Uterine Fibroid Embolization |
| UIP | usual interstitial pneumonitis |
| UGI | upper gastrointestinal |
| ULN | upper limit of normal |
| UNOS | United Network for Organ Sharing |
| UOP, UO, U/O | urinary output |
| Ung | ointment (from Latin unguentum) |
| Unk | unknown |
| UPJ | ureteropelvic junction (see pyeloplasty) |
| UPO | until proven otherwise |
| UPT | urine pregnancy test |
| URA | unilateral renal agenesis |
| URI | upper respiratory infection |
| URS | Ureteroscopy |
| URTI | upper respiratory tract infection |
| US | ultrasonogram |
| USA | unstable angina |
| USG | ultrasonogram |
| USO | unilateral salpingo-oophorectomy |
| USOH | usual state of health |
| USP | United States Pharmacopeia |
| USR | unheated serum reagin |
| USS | ultrasound scan |
| UTI | urinary tract infection |
| UUS | upper uterine segment |
| UVAL | ultraviolet argon laser |
