| Abbreviation | Definition |
|---|---|
| NIAAA | National Institute on Alcohol Abuse and Alcoholism |
| NIAID | National Institute of Allergy and Infectious Disease |
| NIAMS | National Institute of Arthritis and Musculoskeletal and Skin Diseases |
| NIBIB | National Institute of Biomedical Imaging and Bioengineering |
| NICCL | National Incident Communications Conference Line |
| NICE | National Institute for Health Clinical Excellence |
| NICE | National Institute for Health & Clinical Excellence |
| NICHD | National Institute of Child Health and Human Development |
| NIDA | National Institute on Drug Abuse |
| NIDCD | National Institute on Deafness and Other Communication Disorders |
| NIDCR | National Institute of Dental and Craniofacial Research |
| NIDDK | National Institute of Diabetes and Digestive and Kidney Diseases |
| NIDPOE | Notice of Initiation of Disqualification Proceeding and Opportunity to Explain |
| NIDR | National Institute of Dental Research (see NIDCR) |
| NIDRR | National Institute on Disability and Rehabilitation Research |
| NIEHS | National Institute of Environmental Health Sciences |
| NIFC | National Interagency Fire Center |
| NIGHT | Norditropin (somatropin) Injection Growth Hormone Therapy |
| NIGMS | National Institute of General Medical Sciences |
| NIH | National Institutes of Health |