Health misinformation online: how it spreads & why it harms

The U.S. Surgeon General defines health misinformation as information that is false, inaccurate or misleading according to the best evidence available at the time.

Most people who share it are not trying to trick anyone. They want to warn or help others, and don’t realize the information is wrong.

Disinformation is created or shared deliberately, knowing it is false. Health experts group fake news, misinformation and disinformation together because all of them can affect how people make health choices.

Some health disinformation is made to sell a product. The U.S. Food and Drug Administration (FDA) warns that health fraud often uses phrases like “miracle cure” or “secret ingredient”.

The World Health Organization (WHO) describes an infodemic as too much information, including false or misleading information, in digital and physical spaces during a disease outbreak.

WHO says an infodemic causes confusion and risk-taking that can harm health, and leads to mistrust in health authorities.

You don’t need an outbreak to feel this. A flood of conflicting advice about sleep, food or stress can leave anyone overwhelmed and unsure what to believe.

Misleading information is part of the definition, not only outright lies. A real study can be described as proving more than it did, or a small finding can be presented as a cure.

Common forms

• A headline that says more than the article does
• A personal story presented as proof for everyone
• A real number with the comparison left out
• Old advice shared as if it were new

A 2021 systematic review looked at 69 studies of health misinformation on social media. It was most common in studies about smoking and substance use, reaching 87% of posts in some studies.

Average levels the review reported

• Diets and pro–eating disorder content: about 36%
• Diseases: about 40%
• Medical treatments: about 30%
• Vaccines: about 43%

A 2022 WHO review of reviews found misinformation in up to 51% of posts about vaccines, up to 28.8% of posts about COVID-19 and up to 60% of posts about pandemics.

The same review also found that social media helped during health crises in some ways, such as improving knowledge and awareness when the content was accurate.

Researchers had cancer experts review the 200 most popular articles about breast, prostate, colorectal and lung cancer shared on social media. About one in three contained false, inaccurate or misleading information.

Of those, 77% contained information the experts judged probably or certainly harmful, such as advice that could delay care, cause toxic effects or waste money.

In early 2020, researchers checked the most-viewed English videos about the new coronavirus on a big video site. More than one in four (27.5%) contained non-factual information, and those videos had over 62 million views.

None of the videos from government or professional sources in that study were misleading. The problem was that accurate videos were often harder to understand and less appealing.

A large study of stories shared on a social network from 2006 to 2017 found false stories were 70% more likely to be reshared than true ones. True stories took about six times as long to reach 1,500 people.

The researchers found false stories were more novel, and replies to them showed more surprise and disgust. New and emotional things are simply more likely to be passed on.

In that same study, the gap between false and true stories stayed even after automated “bot” accounts were removed. Humans drove most of the spread.

This is hopeful too: if people help misinformation spread, people can also help slow it down.

In a study of popular nutrition accounts on a photo-sharing app, lower-quality posts tended to get more engagement than higher-quality ones.

In a 2022 test by a nonprofit research group, new accounts set up as 13-year-olds on a short-video app were shown eating disorder content within about 8 minutes, after briefly pausing on body image videos.

The Surgeon General notes that misinformation can flourish in group texts and email threads among friends and family, where people trust each other.

Trust in the sender is not the same as accuracy of the message. A kind aunt can pass on a myth without meaning any harm.

Hearing a claim again and again makes it feel familiar, and familiar things feel true, even when the source is unreliable. Researchers call this the illusory truth effect.

In a 2025 national poll, 72% of adults had seen health content about weight loss, diet or nutrition on social media in the past month, and 58% had seen content about mental health.

Fewer than one in ten social media users said they trust most of the health information they see there.

In a 2025 study of nutrition videos on a short-video app, only about a third (36%) were completely accurate. Most did not explain risks and benefits.

Short videos rarely have room for sources, dates or “it depends”. That makes them great for sharing experiences and poor for complicated health decisions.

By 2026, about three in ten U.S. adults used AI tools or chatbots at least monthly for health information, up from 17% in 2024.

In 2024, 56% of adults said they were not confident they could tell whether information from AI chatbots was true or false.

MedlinePlus, a free health information service from the U.S. National Institutes of Health, warns about ads designed to look like neutral health information. If a business pays for a site, its information may favor that business.

In 2025, about one in seven U.S. adults (14%) said they regularly turn to influencers for health information and advice. Six in ten of them believed influencers are mostly motivated by money.

WHO’s review found that health misinformation can delay the provision of health care and reduce access to it.

Experts judging cancer articles counted advice that could lead someone to delay treatment as one of the main kinds of harm.

A study of people with curable cancers found those who chose only alternative approaches, instead of standard cancer treatment, had about 2.5 times the risk of dying during the study period.

Misinformation about any treatment can be dangerous. Before starting, stopping or changing any treatment, talk with your clinical provider.

The National Center for Complementary and Integrative Health says some “detox” and “cleanse” programs can be unsafe and falsely advertised. They can cause dehydration and, with days of no food, dangerous imbalances in the body’s salts.

Juices that haven’t been pasteurized can carry harmful bacteria, which can be serious for children, older people and anyone with a weaker immune system.

The Federal Trade Commission (FTC) warns about products that claim to cure many different health problems, use fake endorsements and pressure you to “act now”.

Money spent on something that doesn’t work can mean less for care that does. And repeated disappointments can wear down hope.

A review of 20 studies with over 7,000 people found that health anxiety is linked with searching for health information online, and strongly linked with “cyberchondria”: distressing, repeated searching that makes worry worse.

The NHS lists looking at health information on the internet over and over as one sign of health anxiety. It suggests keeping a diary of how often you look things up, then slowly cutting back.

WHO says too much information, true and false, causes confusion and risk-taking. When every source says something different, some people freeze and others give up on advice altogether.

Feeling overwhelmed by health news is a normal reaction to an unusual amount of information. It doesn’t mean you’re bad at this.

WHO says infodemics lead to mistrust in health authorities. Some false claims say doctors are hiding the “real” cure, which the FDA flags as a common sign of health fraud.

Researchers say the part that past bad experiences with health care play in mental health misinformation needs more study. If you’ve had those experiences, they are real and deserve to be heard.

A 2024 review found mental health misinformation on social media is common, though how common varies by condition and treatment.

Some health myths suggest people get sick because they didn’t try hard enough or buy the right thing. That can leave people feeling guilty for a health problem that isn’t their fault.

Disagreements about health claims can also cause tension at home. The section on helping friends and family below has gentle ways to talk.

In 2026, 17% of adults who use social media for health said not having a regular provider or not being able to afford one was a major reason. That rose to about three in ten uninsured adults (32%) and LGBT adults.

The top reasons people give for using social media for health are wanting to hear from others with the same condition (36%) and wanting information or support right away (35%).

Both are very human needs. Peer stories can offer real comfort. They just work best alongside reliable facts and professional advice.

A U.S. national study found only 12% of adults had “proficient” health literacy, meaning they could easily use complex health information. About 14% had below basic skills.

When accurate information is hard to understand, simple and catchy myths can win. That is a design problem, not a personal failing.

Younger adults, Black and Hispanic adults, and people with lower incomes are more likely to use social media for health information at least monthly.

Among adults aged 18 to 29, about one in four (23%) regularly turn to influencers for health advice.

The Surgeon General’s advice is to check health information with trustworthy, credible sources before passing it on, and to hold back if you’re unsure.

Before you forward

• Ask: who made this, and how do they know?
• Check the date
• Look for the same claim on a trusted health site
• Notice if it is making you feel angry or scared

The Surgeon General suggests that if someone you care about believes something false, you may get further by first trying to understand rather than judging.

The Surgeon General’s community toolkit suggests listening, showing empathy and avoiding a quick fact-check that may shut the conversation down.

Try saying

• “What made that post stand out to you?”
• “I can see why that worried you.”
• “Want to look it up together?”

The toolkit advises against publicly shaming people. A private message or a quiet chat feels safer than a comment under their post.

Using inclusive, respectful language helps people stay open to new information.

The toolkit suggests pointing people to credible sources they can check themselves. Government health agencies, medical schools and large health nonprofits are good places to start.

Libraries, community health workers, faith groups, schools and local clinics can be places to talk through confusing health claims with people you trust.

The Surgeon General calls for a whole-of-society effort, from families and educators to health workers and tech companies.