Online health advice for people with diabetes is often too complex to understand, analysis suggests.
Language used was beyond average comprehension
A scientist at Bath University looked at pages about diabetes on 15 internet health sites run mainly by charities and official bodies.
He found people would need a reading ability of an educated 11 to 17-year-old to understand the sites.
However, he said the average reading age of people in the UK was equivalent to an educated nine-year-old.
Dr Maged Boulos from Bath University found the NHS Direct Online site was the hardest to understand.
People would need the reading ability of an educated person aged 16 to comprehend information, he estimated.
Other difficult sites were NetDoctor.co.uk, Juvenile Diabetes Research Foundation UK, and the British Diabetic Association which required a reading age of at least 15.
Sites with scores closer to the ability of the average Briton were NHS Prodigy, University College London Hospitals NHS Trust and BestTreatments.
Dr Boulos said much of the online diabetes information needed "considerable rewriting" to match the general reading level of the UK population and avoid "potentially serious consequences".
"Sizeable proportions of Western populations have limited language and maths skills making it difficult for them to fully and safely understand and act upon online health information.
"Public and patient health information that is difficult to understand or liable to misunderstanding by the lay consumer could result in serious consequences."
He said health providers should consider other ways of getting health information to the public, such as face-to-face education and videos.
A Department of Health spokesman said: "We welcome feedback about the website and are keen to ensure that the information provided is as clear and user-friendly as possible.
"That's why we involve users in the development of the website.
"For example, we have a reader's panel of lay-reviewers who feed back to us on a regular basis.
"Furthermore, the website is underpinned by a 24-hour telephone line staffed by nurses and highly trained call handlers. These staff can go through any
information on the website that users do not fully understand."
A spokeswoman from the Juvenile Diabetes Research Foundation said its website's main role was that of funding diabetes research.
"As such, our website is focused on providing in-depth information on the search for a cure to our key audiences - scientists and supporters.
"The website also contains general information on diabetes, its symptoms and treatments accompanied by a clear recommendation that guidance should be sought from a healthcare professional.
"We try to make all our information as clear as possible and welcome any feedback," she said.