| Abbreviation | Definition |
|---|---|
| NI | neutralization index |
| NI | nicotine |
| NI | nifedipine |
| NI | nimesulide |
| NI | nitrogen index |
| NI | nitrogen intake |
| NI | noise index |
| NI | non-invasive |
| NI | nonischemic |
| NI | nosocomial infection |
| NI | not isolated |
| NI | nuclear inclusion |
| NI | nuclear index |
| NI | nucleus intercalatus |
| NI | nucleus interpositus |
| NI | Nursing Informatics |
| NI | nutritional index |
| NIAS | Northern Ireland Ambulance Service |
| NICE | National Institute for Health & Clinical Excellence (NICE) |
| NICECHTEXX | National Institute for Health and Clinical Excellence Centre for Health Technology Evaluation |