Police officers hooked on drugs or alcohol will be given help to overcome their problems, rather than automatically facing the sack.
Where Thames Valley officers are suspected of taking drugs they can be challenged to take a test.
However, there is no policy in the force of compulsory random tests for officers.
Officers with a problem will be given support to get clean. However, those caught committing an offence -- such as being in possession of controlled drugs -- will still face prosecution followed by disciplinary action.
Thames Valley Police's comments follow national reports that senior officers in Metropolitan Police were concerned about heroin and cocaine use by new, younger recruits.
Chief Constable Peter Neyroud said: "Our approach is supportive if somebody has got an addiction problem."
He said alcohol abuse was much more likely than police officers taking drugs. But he emphasised neither was widespread within the force.
Officers suspected of taking drugs could be challenged to take a test, but Mr Neyroud said it was rare for the force to have to do this.
Chief Insp Carole Haveron, of Thames Valley Police's corporate health department, said: "Force policy clearly states that intoxication by any means while a member of staff is on duty will not be tolerated.
"It will be dealt with using our disciplinary procedures, if necessary. However, if a member of staff was to approach the department with a problem, such as addiction, that person would be offered full support in overcoming their condition and continuing their police career if appropriate."
Like the Met, Thames Valley Police is recruiting large numbers of probationer constables, with less than two years' experience.
However, Mr Neyroud said the typical age of someone joining Thames Valley was still about 26 or 27. In previous years it was younger.
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