Number Needed to Harm
- The number of patients required for a specific treatment to cause harm in one of them. It is the converse of the number needed to treat. It is often referred to as NNH. It is the reciprocal of the absolute risk increase (NNH = 1/ARI). Unlike NNT, with NNH large numbers are better than small, because the adverse effect will occur less frequently.
- acronymNNH (written as number needed to harm)