The number needed to harm (NNH) is an epidemiological measure that indicates how many persons on average need to be exposed to a risk factor over a specific period to cause harm in an average of one person who would not otherwise have been harmed. Lower NNT and higher NNH treatments are preferred over those with higher NNT and lower NNH. For NNH, large numbers are good, because they mean that adverse events are rare. Even higher (triple‐digit) NNHs are usually required for adverse events that pose a significant health risk; for very severe adverse outcomes, NNH. Many new drugs not only have a high NNT and a high price tag, but we. Number needed to harm (NNH) corresponds to the number of individuals who must be.