- Intrathoracic - see also condition
- Intrauterine contraceptive device
- Intraventricular - see condition
- Intrinsic deformity - see Deformity
- Intruded tooth 524.34
- Intrusion, repetitive, of sleep (due to environmental disturbances) (with atypical polysomnographic features) 307.48
- Intumescent, lens (eye) NEC 366.9
- Intussusception (colon) (enteric) (intestine) (rectum) 560.0
- Invagination
- Invalid (since birth) 799.89
- Invalidism (chronic) 799.89
- Inversion
- Investigation
- Inviability - see Immaturity
- Involuntary movement, abnormal 781.0
- Involution, involutional - see also condition
- IQ
- IRDS 769
- Irideremia 743.45
- Iridis rubeosis 364.42
- Iridochoroiditis (panuveitis) 360.12
- Iridocyclitis NEC 364.3
