Every week brings a new health headline: a food that prevents cancer, a supplement that boosts focus, a habit that adds years to your life. Some of these are solid. Many are exaggerated. A few are dangerous. The difference is rarely obvious from the headline.

Health literacy is the skill of finding, understanding, and using health information to make good decisions. It isn't medical training. It's knowing which sources to trust, how to read a study or a news story critically, and how to work with clinicians as an informed partner. It is the first step in our Health & Wellbeing learning path, and it borrows heavily from the same thinking as our guide to analyzing data.

✅Key takeaways: (1) Start with public health agencies, medical libraries, and systematic reviews. (2) Ask what kind of study a claim comes from; one study is a clue, not a conclusion. (3) Always look for absolute risk, not just relative risk. (4) Correlation isn't causation, in health as in any data. (5) Be suspicious of miracle claims, testimonials, and anyone selling the cure. (6) Bring written questions to appointments, and use AI chatbots to prepare, never to diagnose.
⚠️Education, not medical advice: This guide teaches how to evaluate health information. It does not diagnose, treat, or replace a qualified clinician. It was reviewed for accuracy against the sources listed, not by a clinician. If you have symptoms or questions about your care, talk to a health professional. In an emergency, call your local emergency number (911 in the US). In the US, you can call or text 988 to reach the 988 Suicide & Crisis Lifeline.

What is health literacy?

Health literacy has two sides:

You control the first one. Low health literacy is common and has nothing to do with intelligence; medical language, confusing forms, and conflicting headlines trip up highly educated people too. The good news is that it's a learnable skill, and the core of it fits on one page.

Step 1: Start with trustworthy sources

Not all health websites are equal. A good default order:

Source type Examples Why trust it
Medical libraries and public health agencies MedlinePlus (US National Library of Medicine), CDC, NIH, the UK's NHS, the World Health Organization Written or reviewed by experts, regularly updated, no products to sell
Systematic reviews Cochrane reviews Combine all good-quality studies on a question and rate the strength of evidence
Professional medical organizations Specialty societies and their patient pages Reflect clinical guidelines, though check for industry funding
Academic medical centers Patient education pages from major hospitals and universities Clinically reviewed; may favor their own services
News outlets Health reporting from established outlets Useful for awareness, but often simplified or exaggerated; trace back to the study
Social media, forums, and influencers Videos, posts, community groups Good for lived experience and support; poor for facts unless they cite sources you can check

Before trusting any page, check four things:

  1. Who wrote or reviewed it, and what are their qualifications?
  2. When was it last updated? Medical guidance changes.
  3. Who pays for the site? Is it selling a product, test, or supplement?
  4. Does it cite sources you can follow back to research or official guidance?

Step 2: Know what kind of study you're looking at

Health claims rest on research, and research comes in very different strengths. From weakest to strongest, roughly:

  STRONGER EVIDENCE
        ^
        |   Systematic reviews and meta-analyses of good trials
        |   Randomized controlled trials (RCTs)
        |   Cohort studies (follow groups over time)
        |   Case-control studies (compare people with and without a condition)
        |   Case reports, expert opinion
        |   Lab and animal studies (early clues, not proof in people)
        |   Anecdotes and testimonials
  WEAKER EVIDENCE

A few more questions to ask about any study:

Step 3: Read risk numbers correctly

This is the single most useful skill in health literacy, and it's simple once you see it.

The same result can sound alarming or trivial depending on which you report:

Without the exposure With the exposure How it's often reported
Example A 2 in 1,000 3 in 1,000 "50% higher risk!" (relative)
Same data 0.2% 0.3% "1 extra case per 1,000 people" (absolute)
Example B 20 in 100 30 in 100 "50% higher risk!" (relative)
Same data 20% 30% "10 extra cases per 100 people" (absolute)

Both examples are "50% higher," but Example B affects 100 times as many people. When a headline gives only a relative number, look for the absolute one before reacting.

The same idea applies to benefits. A treatment that "cuts risk in half" might move risk from 2% to 1%. Clinicians sometimes express this as the number needed to treat (NNT): how many people need the treatment for one to benefit. Here it's 100. That can still be very worthwhile, depending on the condition, the cost, and the side effects, but it's a different picture from "cuts risk in half."

Step 4: Correlation is not causation, in health too

Our data analysis guide covers this in general. In health, it shows up constantly:

When a headline says a food, habit, or supplement "is linked to" an outcome, read it as "is associated with, for reasons we don't fully know yet."

Step 5: Spot misinformation and health scams

Red flags:

In the US, dietary supplements don't go through the FDA approval process for safety and effectiveness that prescription drugs do before they're sold. Tell your clinician and pharmacist about every supplement you take.

Health scams use the same manipulation playbook as other scams: urgency, authority, and fear. Our guide to spotting phishing and social engineering covers those tactics, and they transfer directly.

Step 6: Use AI chatbots carefully

AI assistants can be genuinely helpful for health literacy: explaining a term in plain English, summarizing what a type of test measures, or helping you write questions for an appointment. They also have real limits:

Use them to prepare and understand, then confirm with trusted sources and a clinician. Never use them to diagnose yourself, change a medication, or decide whether something is an emergency. Our Claude vs ChatGPT vs Gemini comparison covers how the major assistants differ.

Step 7: Get more out of appointments

Health literacy matters most in the room with a clinician. Before you go:

The Ask Me 3 program, developed to improve patient-clinician communication, suggests three questions:

  1. What is my main problem?
  2. What do I need to do?
  3. Why is it important for me to do this?

During the visit:

Step 8: Understand the money side

Health decisions are also financial ones. A few terms worth knowing in US health insurance:

Term What it means
Premium What you pay each month to have coverage
Deductible What you pay for covered care each year before the plan starts sharing costs
Copay A fixed amount for a service, such as a doctor visit
Coinsurance Your percentage share of costs after the deductible
Out-of-pocket maximum The most you'll pay for covered care in a year; after that, the plan pays 100% of covered services
In-network vs out-of-network Providers with a contract with your plan cost you less

Our budgeting and emergency fund guide covers planning for medical costs, and how to afford a career change covers keeping coverage between jobs.

A one-minute checklist for any health claim

  1. Who's saying it, and do they profit from it?
  2. What's the evidence: anecdote, lab study, observational study, trial, or systematic review?
  3. How big is the effect in absolute terms?
  4. Who was studied, and are they like you?
  5. What do trusted sources (public health agencies, medical libraries, systematic reviews) say?
  6. What would your clinician say? Ask.

Frequently asked questions

What are the most reliable health websites?

Public health agencies and medical libraries are the best starting points: MedlinePlus, the CDC, and the NIH in the US; the NHS in the UK; and the World Health Organization globally. Cochrane publishes systematic reviews that summarize the evidence on specific questions.

How can I tell if a health study is good?

Check the study type (randomized trials and systematic reviews are strongest), the number and kind of people studied, what was actually measured, whether it was peer reviewed, who funded it, and whether other studies found the same thing.

What's the difference between relative and absolute risk?

Relative risk compares groups ("50% higher"). Absolute risk tells you the actual chance ("3 in 1,000 instead of 2 in 1,000"). Always look for the absolute number before deciding how worried to be.

Can I trust AI chatbots for health questions?

Use them to understand terms and prepare questions, then confirm with trusted sources and a clinician. They can be wrong and don't know your history, so don't use them to diagnose or change treatment.

Check your understanding

Answer each question from memory before opening it. Recalling, not rereading, is what makes learning stick (here's why).

1 A headline says a food 'raises cancer risk by 50%.' What is the first number you should look for?

The absolute risk: how many people out of 100 (or 1,000) get the disease with and without the food. A 50% relative increase from 2 in 1,000 to 3 in 1,000 is one extra case per 1,000 people.

2 An observational study finds that people who drink more tea live longer. Why can't it prove that tea causes longer life?

Tea drinkers may differ in other ways (income, diet, exercise, smoking) that affect lifespan. Observational studies show associations; randomized controlled trials are needed to test cause and effect.

3 What kind of evidence usually deserves the most weight on a health question?

Systematic reviews and meta-analyses of good randomized controlled trials, because they combine many studies instead of relying on one.

4 Name three red flags that a health claim may be misinformation.

Any three of: a miracle cure for many conditions, 'doctors don't want you to know,' testimonials instead of studies, pressure to buy now, claims that a product is 'natural so it's safe,' or a seller who also profits from the claim.

5 What are the three Ask Me 3 questions to bring to an appointment?

What is my main problem? What do I need to do? Why is it important for me to do this?

Where to go next

You've finished step 1 of the Health & Wellbeing path. Next:

Sources

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