China 
Africa 
- Ultramicroscope
- Ultramicrotomy
- Ultrasensitivity
- Ultrasonic cleaning
- Ultrasonic wave
- Ultrasonics
- Ultrasonography
- Ultrasound biomicroscopy
- Ultrasound energy
- Ultrasound therapy
- Ultrasound transducer
- Ultrasounds
- Ultrastructure
- Ultraviolet
- Ultraviolet germicidal irradiation
- Ultraviolet light
- Ultraviolet spectrum
- Umbelliferone
- Umbellulone
- Umbilical arteries
- Umbilical artery
- Umbilical cord
- Umbilical cord compression
- Umbilical cord prolapse
- Umbilical fascia
- Umbilical fold
- Umbilical folds
- Umbilical hernia
- Umbilical region
- Umbilical ring
- Umbilical vein
- Umbilical venous catheter
- Umbilicus
- Umbralisib
- Umbrella review
- Umeclidinium
- Umeclidinium bromide
- Umwelt
- Unani medicine
- Uncanny Valley
- Uncaria
- Uncaria rhynchophylla
- Uncaria tomentosa
- Uncertainty
- Uncertainty avoidance
- Uncinate fasciculus
- Uncinate process
- Uncombable Hair Syndrome
- Uncombable hair syndrome
- Uncompetitive inhibitor
- Unconditional positive regard
- Unconditioned stimulus
- Unconscious
- Unconsciousness
- Unconventional protein secretion
- Uncoupler
- Uncoupling
- Uncoupling protein
- Uncus
- Undecanal
- Undecaprenyl phosphate
- Underactive bladder
- Underactive thyroid
- Underarm hair
- Underdevelopment
- Underinsured
- Undernourishment
- Undernutrition in children
- Understanding
- Undertreatment of pain
- Undifferentiated connective tissue disease
- Undue influence
- Unequal crossing over
- Unethical human experimentation
- Unexplained infertility
- Unfolded protein response
- Ungual
- Unguent
- Unhealthy diet
- UniFrac
- UniGene
- UniProt
- Unicameral bone cyst
- Unicentric Castleman disease
- Unicornuate uterus
- Uniformly most powerful test
- Unilamellar liposome
- Unilateral hearing loss
- Unimodal distribution
- Unintended consequences
- Uniparental disomy
- Unipolar neurons
- Uniporter
- Units of selection
- Univariate
- Universal Design
- Universal Immunisation Programme
- Universal Precautions
- Universal flu vaccine
- Universal health care
- Universal neonatal hearing screening
- Universal testing machine
- University of Pennsylvania Smell Identification Test
- Unoprostone
- Unsaturated fat
- Unsaturated fatty acids
- Unspecified feeding or eating disorder
- Unstable angina
- Unsteady gait
- Untranslated regions
- Unverricht-Lundborg disease
- Unwarranted variation
- Up-and-down procedure
- Upadacitinib
- Upper abdominal pain
- Upper airway resistance syndrome
- Upper esophageal sphincter
- Upper eyelid
- Upper gastrointestinal bleeding
- Upper limb
- Upper motor neuron
- Upper motor neuron lesions
- Upper motor neuron syndrome
- Upper quartile
- Upper respiratory infection
- Upper respiratory tract
- Upper respiratory tract infection
- Upper subscapular nerve
- Upper trunk
- Upregulated
- Upregulation
- Upstream activating sequence
- Upstream open reading frames
- Urachal cyst
- Urachal fistula
- Urachus
- Uracil
- Uracil phosphoribosyltransferase
- Uracil-DNA glycosylase
- Urapidil
- Urate
- Urea
- Urea breath test
- Urea cycle
- Urea reduction ratio
- Urea transporter
- Ureaplasma
- Ureaplasma urealyticum
- Ureas
- Urease