| I&I | Industrial & Institutional (cleaning) |
| IAA | 3-Indole Acetic Acid |
| IAB | Intellectual Asset Business |
| IACM | Intl. Association of Color Manufacturers |
| IAPV | Israel Acute Paralysis Virus |
| IAQ | Indoor Air Quality |
| IAR | Illuminance Anisotropic Ratio |
| IB | Inter Body (Orthopaedics>Spine) |
| IBAO | Iso Butyl Alumin Oxane |
| IBAT | Ileal Bile Acid Transporter |
| IBATi | Ileal Bile Acid Transport inhibitor |
| IBCC | Instituto Brasileiro de Controle do Câncer |
| IBD | Inflammatory Bowel Disease |
| IBD AH | Infectious Bursal Disease |
| IBMA | Iso Butyl Meth Acrylate |
| IBP | Ice Binding Protein |
| IBS | Irritable Bowel Syndrome |
| IBS-C | IBS with Constipation |
| IBS-D | IBS with Diarrhea |
| IBTBE | Iso Butyl Tert. Butyl Ether |
| IBV | Infectious Bronchitis Virus (poultry) |
| IC | Integrated Circuit |
| ic | Intra Cellular |
| IC | Interstitial Cystitis |
| ICAM | Inter Cellular Adhesion Molecule |
| ICAT | Isotope Coded Affinity Tags (Proteomics; Protein Expression Profiling) |
| ICB | Institute for Collaborative Biotechnologies (USA) |
| ICBR | Integrated Corn-based Bio Refinery |
| ICBT | Intra Cavitary Brachy Therapy |
| ICCB | Institute of Chemistry & Cell Biology (Harvard) |
| ICD | Implantable Cardioverter Defibrillators |
| ICE | Improved Chemical Identity (Pharma.) |
| ICE | IL Convertase Enzyme |
| ICE Cardio | IntraCardiac Echocardiography |
| ICF | Insulating Concrete Forms |
| ICF Neuro | Intra Cranial Fluids |
| ICG | Indo Cyanine Green |
| iCGM | integrated continuous glucose monitoring |
| ICI | Imperial Chemical Industries (UK Co.) |
| ICM | Implantable Cardiac Monitor |
| ICN | Inactive Corp. Name |
| ICP | Insecticidal Crystal Protein |
| ICP | Inductively Coupled Plasma |
| ICP Neuro | IntraCranial Pressure |
| ICP-MS | Inductively Coupled Plasma Mass Spectrometry |
| ICR | Ion Cyclotron Resonance |
| ICR | Institute of Cancer Research (London, UK) |
| ICS | Inhaled Cortico Steroid |
| ICSI | Intra Cytoplasmic Sperm Injection |
| ICT | Information and Communications Technology |
| ICT Contro | Info. & Control Technology |
| ICU | Intensive Care Units |
| ID | IDentification; IDentity |
| IDA | Iron Deficiency Anemia |
| IDC | Inheritable Dilated Cardiomyopathy |
| IDDM | Insulin Dependent Diabetes Mellitus |
| IDE | Investigational Device Exemption |
| IDE | Integrated Design Environment |
| IDE | Insulin Degrading Enzyme |
| IDH | Isocitrate De Hydrogenase |
| IDO | Indoleamine-2,3-DiOxygenase |
| IDP | Intrinsically Disordered Protein |
| IDS | Iduronate 2-Sulfatase (enzyme) |
| IE | IrEland |
| IED | Improvised Explosive Device |
| IEG | Inhibitory Enterocyto Genin |
| IEM | Isocyanato Ethyl Methacrylate |
| IEM | Image Enhancing Moieties |
| IEM Ear | In-Ear Monitor |
| IER | Ion Exchange Resin |
| IET | Integrated Environmental Technologies |
| IF | Intrinsic Factor |
| IF | Impact Fluidity |
| IF | Inorganic Fullerenes |
| IFC | Integrated Fluidic Circuits |
| IFE | In Flight Entertainment |
| IFM | Intelligent Flash Management |
| IFN | Interferon |
| IG | Immuno Globulin |
| IGA | Immuno Globulin A |
| IgAN | Immuno globulin A Nephropathy |
| IGB | IntraGastric Balloon |
| IGCC | Integrated Gasification Combined Cycle (clean coal power plant) |
| IGE | Immuno Globulin Epsilon |
| IGE | Immuno Globulin E |
| IGF | Insulin Growth Factor |
| IGF-IR | IGF I Receptor |
| IGFBP | IGF Binding Protein |
| IGG | Immuno Globulin G |
| IgG1 | Immuno globulin Gamma 1 |
| IGIV | Immune Globulin Intra Venous |
| IGM | Inheritable Genetic Modification |
| IGM | Immuno Globulin M |
| IGS | Integral Glycan Sequencing |
| IGS Cardio | image guided system |
| IGT | Impaired Glucose Tolerance |
| IHC | Immuno Histo Chemistry |
| IHHS | International HyperHidrosis Society |
| IHN | Infectious Hematopoietic Necrosis |
| IHNV | Infectious Haematopoietic Necrosis Virus |
| IHT | Induced Hemorrhagic Time |
| IIM | Industrial & Institutional Market |
| IISRP | International Institute of Synthetic Rubber Producers (USA) |
| IL | Inter Leukin |
| IL | IsraeL |
| ILBM | In-Line Blood Monitor |
| ILD | Inter Layer Dielectric |
| ILED | InOrganic Light Emitting Diode |
| ILGF | Insulin Like Growth Factor |
| ILK | Integrin Linked Kinase |
| ILM | Intraoperative Lymphatic Mapping (Oncology) |
| ILR | intraocular lens replacement |
| ILT | Infectious LaryngoTracheitis |
| IM | Infectious Mononucleosis |
| IM | Intra Muscular |
| IM | Industrial Maintenance |
| IMAC | Immobilized Metal Affinity Chromatography |
| IMAG | IMAGing |
| IMC | Inert Matrix Composition |
| IMCVD | Immune-Mediated Cochlear or Vestibular Disorder |
| IMH | Intra Mural Hematoma |
| IMI | Imidazolinone (Herbicide) |
| IMI | Inferior Myocardial Infarction |
| IMIDs | Immune Mediated Inflammatory Diseases |
| IMM | Institut fuer Mikrotechnik Mainz |
| IMP | Inosine 5-Mono Phosphate |
| IMPDH | IMP De Hydrogenase |
| IMRI | Intra-operative MRI guidance |
| IMRT | Image-guided, intensity-Modulated Radiation Therapy |
| IMS | Ion Mobility Spectrometry |
| IN | INdia |
| INCA | Instituto Nacional do CAncer (Brazil's Ministry of Health) |
| INCI | International Nomenclature of Chemical Ingredients |
| IND | Investigational New Drug |
| INDA | Investigational New Drug Application |
| INEEL | Idaho National Engineering & Environmental Laboratory (USA Federal Gov.). |
| INFO | INFOrmation |
| INGAP | Islet Neogenesis Associated Protein |
| INN | International Nonproprietary Name |
| INOS | Inducible form of NOS |
| INSERM | Institut Santé et Recherche Médicale (France) |
| INSYRT | IN situ lipid SYnthesis for protein Reconstitution Technology |
| IO | Intra Osseous |
| IOIS | Idiopathic Orbital Inflammatory Syndrome |
| IOL | Intra Ocular Lens |
| IOP | Increased Ocular Pressure |
| IOP | Intra Ocular Pressure |
| IORT | Intra Operative Radiation Therapy |
| IP | Intellectual Property |
| IP | Internet Protocol |
| IPA | Iso Phthalic Acid |
| IPA | Iso Propyl Alcohol |
| IPAH | Idiopathic Pulmonary Arterial Hypertension |
| IPAM | IP Address MAN. |
| IPBC | 3-Iodo-2-Propynyl-N-Butyl Carbamate (biocide) |
| IPC | Inositol Phosphoryl Ceramide |
| IPD | Invasive Pneumococcal Disease |
| IPDI | Iso Phorone Di Isocyanate |
| IPEN | Instituto de Pesquisas Energeticas e Nucleares (Brazil) |
| IPF | Idiopathic Pulmonary Fibrosis |
| IPI | Inactive Pharma. Ingredients |
| IPL | Intense Pulsed Light |
| IPM | Integrated Pest Management |
| IPN | Interpenetrating Polymer Network |
| IPO | Initial Public Offering |
| IPR | inter partes review |
| IPS | Induced Pluripotent Stem |
| IPSC | Induced Pluripotent Stem Cells |
| IPT | Inductive Power Transfer |
| IQF | Individually Quick Frozen (food: green vegetable) |
| IR | Infrared |
| IR | Immediate Release (Pharma.) |
| IRDS | Infant Respiratory Distress Syndrome |
| IRED | Infra Red Emitting Diode |
| IRFNA | Inhibited Red Fuming Nitric Acid (oxidizer) |
| IRMOF | Iso Reticular Metal-Organic Frameworks |
| IRO | Independent Review Organizations |
| IRP | Iron Regulating Proteins |
| IRS | Insulin Resistance Syndrome |
| IRT | Interactive Response Technology |
| IRTK | Insulin Receptor Tyrosine Kinase |
| IS | ISland |
| IS Neuro. | Infantile Spasms |
| ISDR | Interferon Sensitivity Determining Region |
| ISDT | Initial Specimen Diversion Technique |
| ISE | Ion Selective Electrode |
| ISM | indolent systemic mastocytosis |
| ISN | Institute for Soldier Nanotechnologies (linked to MIT) |
| ISR | in-stent restenosis |
| ISS | Idiopathic Short Stature |
| IST | Individual Spinning Titre |
| IT | Information Technology |
| IT | Iso Thiazolin |
| IT | ITaly |
| ITA | Investigational Testing APP. |
| ITAM | Immunoreceptor Tyrosine-based Activation Motif |
| ITC | International Trade Commision (USA) |
| ITCC | Intelligent Torque Controlled Coupling (Automotive) |
| ITD | internal tandem duplication |
| iTNM | implantable TNM |
| ITO | Indium Tin Oxide |
| ITP | Idiopathic Thrombocytopenic Purpura |
| ITP | Immune Thrombocytopenic Purpura |
| ITRI | Industrial Technology Research Institute (Taiwan) |
| ITRS | Intl. Technology Roadmap for Semiconductors |
| ITS | Internal Transcribed Spacer |
| IUC | Intra Uterine Contraception |
| IUD | IntraUterine Device |
| IUGR | Intra Uterine Growth Retardation |
| IUI | Iatrogenic Ureteral Injury |
| IUPAC | International Union of Pure & Applied Chemistry |
| IV | Intra Venous |
| IV | Intrinsic Viscosity |
| IV | Incremental Vaccination |
| IVC | IntraVaginal Culture |
| IVD | in vitro diagnostic |
| IVDR | In Vitro Diagnostic medical devices Regulation |
| IVF | in vitro fertilisation |
| IVI | IntraVaginal Insemination |
| IVIG | Intra Venous Immuno Globulin |
| IVL | IntraVascular Lithotripsy |
| IVR | Interactive Voice Response |
| IVRS | Interactive Voice Response Systems |
| IVS | Intelligent Vehicle Support |
| IVUS | Intra Vascular Ultra Sound |
| IVWMS | IV Workflow MAN. System |
| IWL | Involuntary Weight Loss |
| IWR | Interactive Web Response |