| Term | Definition / Meaning / Stand for |
| IRM |
Image Reconstruction Method |
| IHA |
Immune Hemolytic Anemia |
| IRIS |
Immune Reconstitution Inflammatory Syndrome |
| IY |
Immunized Youth |
| IBF |
Immuno-blotting Factors |
| ICF |
Immunocellular Fraction |
| IS |
Immunosuppressed |
| IT |
Immunotherapy |
| IHR |
Incidence-Hazard Ratio |
| IPA |
Indole-3-Pyruvate |
| IDD |
Infectious Disease Diagnosis |
| ID |
Infectious Disease |
| ISR |
Inflammatory Stress Response |
| ISG |
Interferon-Stimulated Genes |
| IL-10 |
Interleukin 10 |
| IL-12 |
Interleukin 12 |
| IL-18 |
Interleukin 18 |
| IL-1 |
Interleukin 1 |
| IL-23 |
Interleukin 23 |
| IFP |
Intermediate Filament Protein |
| ISD |
Internal Sphincter Disease |
| IPP |
Interpupillary Distance |
| IF |
Interstitial Fluid |
| IWL |
Intra-abdominal Weight Loss |
| IAD |
Intra-abdominal pressure |
| ITL |
Intra-thoracic Lesions |
| IIB |
Intracellular Inhibitory Binding |
| IC |
Intracellular |
| IOC |
Intraocular Pressure |
| IO |
Intraosseous |
| IP |
Intraperitoneal |
| IK |
Ion channel Kinase |
| IHP |
Ischemic Hepatic Parenchyma |
| IDH |
Isocitrate Dehydrogenase |
| ISA |
Isoenzymes of Sucrase |
| IHT |
Isotonic Hypotonic Therapy |
| IIM |
Idiopathic Inflammatory Myopathy |
| IPF |
Idiopathic Pulmonary Fibrosis |
| ITP |
Idiopathic Thrombocytopenic Purpura |
| ITP |
Immune Thrombocytopenic Purpura |
| IgA |
Immunoglobulin A |
| IgB |
Immunoglobulin B |
| IGD |
Immunoglobulin D |
| IgD |
Immunoglobulin D |
| IGE |
Immunoglobulin E |
| IgE |
Immunoglobulin E |
| IGG |
Immunoglobulin G |
| IgG |
Immunoglobulin G |
| IGM |
Immunoglobulin M |
| IgM |
Immunoglobulin M |
| ICD |
Implantable Cardioverter Defibrillator |
| IVD |
In Vitro Diagnostic |
| IVF |
In Vitro Fertilization |
| IICP |
Increased Intracranial Pressure |
| IFA |
Indirect Immunofluorescence Assay |
| IVC |
Inferior Vena Cava |
| IBD |
Inflammatory Bowel Disease |
| IRB |
Institutional Review Board |
| IDE |
Insulin Degrading Enzyme |
| IGF |
Insulin-like Growth Factor |
| IR |
Insulin Resistance |
| IQ |
Intelligence Quotient |
| ICU |
Intensive Care Unit |
| ICS |
Intercostal Space |
| IFN |
Interferon |
| IRF |
Interferon Regulatory Factor |
| IL-2 |
Interleukin 2 |
| IL-6 |
Interleukin 6 |
| IL |
Interleukin |
| IMV |
Intermittent Mandatory Ventilation |