People with hearing problems in need of health care often receive a poor service, according to research carried out by the Royal National Institute for Deaf People.
RNID estimates that the NHS is wasting £20m a year because almost one in four deaf patients misses appointments due to poor communication.
BSL interpreters help avoid misunderstandings
Among British Sign Language users who took part in the survey, a third were either unsure of the correct dosage of prescribed medication or had taken too much or too little because of a communication problem.
And 70% of BSL users admitted to accident and emergency were not provided with a sign language interpreter.
"The NHS can easily address this situation with simple and cost effective solutions," said RNID chief executive John Low.
"Minor investment in simple technologies such as visual alert displays and loop systems will improve access and help lower the number of missed appointments.
"However, to be truly effective, this investment needs be followed by deaf awareness training for all frontline NHS staff."
RNID surveyed more than 800 deaf and hard of hearing people about their experiences of visiting GP surgeries and hospitals in December last year.
RNID's message to health professionals
In a statement the Department of Health said it was "committed to designing NHS service delivery around the needs of patients".
The statement said that it was up to health service providers to comply with the new provisions of the Disability Discrimination Act.
"The department has issued detailed guidance to the NHS about this including checklists and advice on training for staff."
Once part three of the act becomes law on October 1, all health providers will need to make 'reasonable adjustments' to ensure that their services are fully accessible to disabled people.
In the case of deaf people, these could include the provision of BSL interpreters, hearing loop systems, visual alert displays and video interpreting.
And RNID says that all written communication should be in clear English to help BSL users.
The charity can provide a videophone link to communicate in sign language.
The service connects a deaf and hearing person via videophone to an interpreter at RNID.