KCE Glossary

The average number of patients who need to have the treatment or other intervention for one of them to get the positive outcome in the time specified. 

The closer the number needed to treat is to 1, the more effective the treatment.

For example, if the NNT for drug A compared with drug B for pain relief after a tooth extraction is 4, on average, for every 4 people who get drug A instead of drug B, 1 person will have pain relief after tooth extraction who would not have done if all 4 had got drug B. The other 3 people out of the 4 will have or not have pain relief, just as if they had taken drug B.