- Intuitive eating
- Intussusception
- Intussusceptive angiogenesis
- Inulin
- Invadopodia
- Invagination
- Invariant chain
- Invasin
- Invasive aspergillosis
- Invasive candidiasis
- Invasive ductal carcinoma
- Invasive lobular carcinoma
- Invasive procedure
- Invasive test
- Invasive urothelial carcinoma
- Invasive ventilation
- Invasomes
- Inverse agonists
- Inverse care law
- Inverse dynamics
- Inverse probability weighting
- Inverse psoriasis
- Inverse ratio ventilation
- Inverse-variance weighting
- Inversion recovery
- Invert sugar
- Invertase
- Inverted nipples
- Inverted papilloma
- Inverted repeats
- Investigator's Brochure
- Investing layer of deep cervical fascia
- Invisible disability
- Invisible support
- Involucrin
- Involucrum
- Involuntary action
- Involuntary commitment
- Involuntary euthanasia
- Involuntary treatment
- Involution
- Involutional melancholia
- Inward-rectifier potassium channel
- IoT
- Iodinated contrast medium
- Iodine
- Iodine 123
- Iodine 131
- Iodine compounds
- Iodine deficiency
- Iodine monochloride
- Iodine value
- Iodine-125
- Iodine-129
- Iodine-starch test
- Iodised salt
- Iodized salt
- Iodoacetamide
- Iodoacetic acid
- Iodoform
- Iodophor
- Iodothyronine deiodinase
- Ioflupane
- Iohexol
- Ion channels
- Ion chromatography
- Ion exchange
- Ion exchange chromatography
- Ion exchange resin
- Ion pumps
- Ion semiconductor sequencing
- Ion source
- Ion transport
- Ion trapping
- Ion-exchange membranes
- Ionic compound
- Ionic strength
- Ionization
- Ionization chambers
- Ionization energy
- Ionization potential
- Ionized gas
- Ionizing radiation
- Ionomycin
- Ionophores
- Ionotropic effect
- Ionotropic glutamate receptors
- Ionotropic receptors
- Iontocaine
- Iontophoresis
- Iopanoic acid
- Iopromide
- Ioversol
- Iowa gambling task
- Ipatasertib
- Ipecac
- Ipilimumab
- Ipomoea
- Ipomoea batatas
- Ipragliflozin
- Ipratropium bromide
- Iprodione
- Iproniazid
- Ipsapirone
- Irak4
- Irbesartan
- Iridectomy
- Iridocyclitis
- Iridodialysis
- Iridodonesis
- Iridoids
- Iridology
- Iridoplegia
- Iridoviridae
- Irinotecan
- Iris
- Iris coloboma
- Iris pseudacorus
- Iris scissors
- Iris sphincter muscle
- Irisin
- Iritis
- Iron
- Iron binding capacity
- Iron binding proteins
- Iron cycle
- Iron deficiency
- Iron deficiency anaemia
- Iron deficiency anemia
- Iron lung
- Iron metabolism disorders
- Iron overload
- Iron oxide
- Iron oxide nanoparticles
- Iron oxides
- Iron phosphate
- Iron poisoning
- Iron preparation
- Iron response element
- Iron sucrose
- Iron sulfur proteins
- Iron supplements
- Iron-binding proteins
- Iron-sulfur cluster
- Iron-sulfur proteins
- Irosustat
- Irradiance
- Irradiation
- Irrationality
- Irregular sleep-wake rhythm