| Abbreviation | Definition |
|---|---|
| NIM | No Inspection Made |
| NIMH | National Institute of Mental Health |
| NIMS | National Incident Management System |
| NINDS | National Institute of Neurological Disorders and Stroke |
| NINR | National Institute of Nursing Research |
| NIOSH | National Institute for Occupational Safety and Health |
| NIP | National Immunization Program |
| NIPH | Norwegian Institute of Public Health |
| NIPP | National Infrastructure Protection Plan |
| NIS | National In-patient Sample |
| NISAC | National Infrastructure Simulation and Analysis Center |
| NISAC | National Infrastructure Simulation and Analysis Center (Department of Homeland Security) |
| NIST | National Institute of Standards and Technology |
| NKCA | Natural Killer cell Cytotoxic Activity |
| NLEA | Nutrition Labeling and Education Act of 1990 |
| NLEM | National List of Essential Medicines |
| NLM | National Library of Medicine |
| NLN | Nordiska LäkemedelsNämnden (Nordic Council on Medicines) |
| NLRC | Nicholson Lane Research Center |
| NLT | Not Less Than |