| Abbreviation | Definition |
|---|---|
| IR | Information Request |
| IRA | immediate response authority |
| IRB | Institutional Review Board |
| IRB | Investigational Review Board |
| IRC | Impact Resistance lens Certification |
| IRC | Internet Relay Chat |
| IRDM | Insulin Resistant Diabetes Mellitus |
| IREAS(CDRH) | International Relations and External Affairs Staff (CDRH) |
| IRIS | International Regulatory Issues Staff |
| IRM | Information Resources Management |
| IRMC | Information Resources Management College |
| IRPB | International Research and Programs Branch |
| IRS | Identical, Related, or Similar |
| IRS | Incident Reporting System |
| IRS(OC) | International Relations Staff (OC) |
| IRTA | Intramural Research Training Award |
| IS | Ingredients Statement |
| IS | Intrinsically Safe |
| ISA | Information Systems Architecture |
| ISAC | Information Sharing And Analysis Center |