Mental health bosses have vowed to improve communications after a third of patients said they were not told about the side effects of medication.
Just 66 per cent of inpatients at county mental health units, run by the 2Gether NHS Foundation Trust, said they were told about medical side effects to their medication.
Only 72 per cent of people said they were told about the daily routing of wards on arrival and 70 per cent were involved in their care plan.
However, 91 per cent said they felt safe during their time on the ward according to the survey carried out on dischargae.
Councillor Brian Oosthuysen (Lab, Rodborough) questioned the survey results during a Health, Community and Care Overview and Scrutiny Committee.
He said: "I am disappointed and concerned by these results.
"It is surprising that only two thirds of people were asked and told about the possible side effects."
But chief executive of the trust, Shaun Clee, said all patients would have been told this information and this could be demonstrated through paperwork.
He said: "But that doesn't matter. What matters is that some people don't think they were asked and this is something we will be addressing.
"The most important thing is the service users' views and if they feel this we are disappointed and I want to improve that.
"We are looking at a new technique of getting people to repeat what we have told and explained to them, as research shows people take on board by doing that.
"I know people are getting the information, but we really need to drive up these statistics.
"We do need to do better here and we are aware of this."
Mr Clee explained when in-patients were admitted the information was all provided and staff would tick boxes to clarify it had been done.
The trust runs the 88 bed Wotton Lawn Hospital in Gloucester. It has four admission wards, a nurse led psychiatric intensive care unit and a low secure unit.
It also runs Charlton Lane Hospital, Cheltenham, for those with dementia and older people with mental health problems.
One in four adults experience mental health problems at some point in their life, while one in 10 children are affected.