Average number of injections per day (in treatment)
The aim of opiate substitution treatment (OST) is, of course, to enable people to begin the journey towards becoming drug free. However, for some that journey will be a long one, and for a considerable time while in treatment they may continue to inject.

The frequency of injecting, however, is likely to be far less than it was out of treatment. Studies such as NTORS looked at number of days in the past week/month that people have injected, but did not then go on to ask how many times they injected on those days.

Other factors being equal, the injection frequency is likely to be higher in areas with prescribing regimes that give sub-therapeutic doses, and/or reduced levels of psychosocial support; and lower in areas with high quality treatment delivering therapeutic doses, and good quality psychosocial support in place. Local knowledge is needed when choosing the most appropriate values to enter for this and other variables as other factors may be considered relevant too.

For the purposes of this calculator we have provided a default value for injecting frequency of around once every three days (0.3 per day) – estimated as an average across those who have been stable in OST (and haven’t injected for years) through to those who are ambivalent about treatment (and may still inject every day).