There is too much focus on the potential side-effects of medicines on information leaflets inside packs and not enough on their benefits, says the Academy of Medical Sciences.
Its new report calls for them to be rewritten to give a more balanced view.
A survey by the academy found the public was confused by information on medicines and did not trust scientific research.
Scientists said clear communication with patients was a priority.
The side-effects listed on patient information leaflets (PILs) are often very long and off-putting, the report says.
They make people unduly anxious about taking medicines and could be the reason why fewer than 50% continue with drugs they have started taking.
The likelihood of the side-effects occurring is also rarely explained - instead they are labelled "possible" or "serious".
And the benefits of the medicines are usually understated, taking up much less space on the leaflet than potential harms.
Prof Sir John Tooke, chair of the Academy of Medical Sciences report, says there is too much "impenetrable" scientific language on leaflets.
For example, the leaflet inside a box of paracetamol says that possible side-effects from taking the tablets are the chance of developing pancreatitis or hepatitis.
However, there is no information on what the conditions are or how big the risk of getting them is in reality.
Rather than clearly explaining how symptoms will reduce, too many leaflets describe what the medicine does in complicated biological terms.
"They aren't written from a consumer's perspective," Prof Tooke says.
Patients should feel confident about the medicines they are taking, rather than uneasy.
If they do not understand the information provided, they are less likely to feel good about taking them.
For legal and regulatory reasons, there is a lot of information provided - but the report asks whether it is really there to help the public.
Silvia Kirk is a mother of two from London, who took part in public workshops for the report.
"I don't always read the information leaflets in medicine packs, unless it's for my children - one of whom has asthma," she says.
"Usually my heart is all over the place as I'm reading them, because I'm wondering whether the risks outweigh the benefits.
"Some of the information doesn't make sense at all. When you're poorly you don't want to feel anxious too - and I think it's particularly confusing for older people.
"I understand it all needs to be on the leaflets, but there's too much crammed into one space. I tend to go by what the GP has said and written on the prescription.
"I only check side-effects listed on the Yellow Card website [suspected adverse reactions to licensed drugs], which I find are useful.
"A link to more detailed information online on individual medicines would be useful for me."
Tips on what to ask your GP
- Is this medicine right for me? How will it improve my health?
- What are its potential benefits and risks? Are they relevant to me?
- How will this medicine make me feel? Will it affect my daily life?
- How should I take it? Can I take it with other medication?
The report is also calling for:
- More efficient use of GP appointments, which may need to be longer - particularly for patients with multiple conditions
- A "go to" source of trusted information online about medicines for patients and healthcare professionals
The survey of about 2,000 British adults and 1,000 GPs found that a third of the public trusted evidence from medical research while two-thirds trusted the experiences of family and friends when it came to taking medicines.
Doctors said they also needed better information to help them judge the benefits and harms of medicines for patients.
What do scientists think?
In general, they welcomed the whole idea of making information on medicines clearer - for patients and doctors.
But they recognised that a degree of uncertainty was inevitable in medicine, because scientific research was always evolving.
Dr Louise Brown, senior statistician at the MRC Clinical Trials Unit at University College London, said there were other challenges to face in the shape of the internet and social media.
"We are all bombarded with an unrelenting stream of new information that is overwhelming and very difficult to process.
"Unsurprisingly, this leads to feelings of scepticism and mistrust," she said.
Peter Openshaw, professor of experimental medicine at Imperial College London, said providing accurate and accessible information on new treatments was vital.
"It is only by working in close partnership with patients, clearly and honestly explaining the scientific evidence, that we can fully realise the huge potential that 21st Century medical science offers."