NNH
Medical abbreviation · Medical Research
| Stands for | Number needed to harm |
|---|---|
| Categories | Medical |
NNH stands for Number needed to harm, a medical research abbreviation.
Average number of patients who must receive a treatment for one additional patient to experience a specified harm compared with the control, calculated as 1 divided by the absolute risk increase. It is weighed against the number needed to treat when balancing benefits and risks.
Example: NNT 25 to prevent a stroke versus NNH 200 for a major bleed.
Usage notes
A large NNH is reassuring because the harm is uncommon. Like the NNT, it applies only to a specific outcome, population and time period. Some writers prefer the phrase number needed to treat to harm (NNTH).
Related abbreviations
More medical research abbreviations
- MedDRA – Medical Dictionary for Regulatory Activities
- MeSH – Medical Subject Headings
- MHRA – Medicines and Healthcare products Regulatory Agency
- NCT – National Clinical Trial (number)
- NICE – National Institute for Health and Care Excellence
- NME – New molecular entity
- NNT – Number needed to treat
- NPV – Negative predictive value
- NS – Not significant (statistically)
- ODD – Orphan drug designation
- OHRP – Office for Human Research Protections
- OR – Odds ratio
See all 94 medical research abbreviations →
This entry is for general education and is not medical advice. Abbreviation use varies between institutions; always confirm in context.