Complementary medicine refers to health practices, products or therapies used alongside conventional medical treatment rather than instead of it. The word complementary is important: complementary approaches are intended to complement conventional care, whereas alternative medicine traditionally refers to approaches used in place of conventional treatment. The terminology is not always used consistently, and contemporary organisations may use broader terms such as complementary and integrative medicine or traditional, complementary and integrative medicine.
Examples can include acupuncture, some herbal medicines, massage, yoga, meditation and certain manual therapies, although whether a particular practice is classified as complementary can vary between healthcare systems and definitions. The fact that a therapy is called complementary says nothing by itself about whether it is effective, safe or appropriate.
Complementary medicine is distinct from conventional evidence-based medicine primarily by its therapeutic traditions, practices or evidence base, not because every complementary therapy is necessarily ineffective or every conventional treatment is effective. Some complementary practices have been investigated in clinical trials and may have evidence supporting particular uses, while others have limited, inconsistent or no convincing evidence for the claimed benefits. Evidence needs to be assessed separately for each intervention and indication.
A therapy that may help one symptom does not thereby become an effective treatment for unrelated diseases. Similarly, a therapy can be useful for relaxation or symptom management without treating the underlying disease. Claims should therefore be evaluated according to evidence rather than according to the category label.
Herbal medicines are an important subset because they contain biologically active substances and can therefore produce both effects and adverse effects. NHS guidance advises checking that relevant herbal medicines have a Traditional Herbal Registration mark and product code where applicable and warns against buying unlicensed herbal medicines online. Herbal products can interact with prescription medicines, alter drug concentrations, affect bleeding or cause toxicity. “Natural” does not mean automatically safe, and the concentration and composition of supplements can vary between products. People should tell healthcare professionals about herbal medicines and other complementary therapies they use so potential interactions and duplicated treatment can be considered.
Acupuncture and other physical or mind-body approaches illustrate why evidence must be considered individually. Acupuncture involves inserting fine needles at specified points and has been investigated for a range of pain conditions and other symptoms. Massage, yoga, relaxation and mindfulness may influence pain, stress, mobility or wellbeing through several possible mechanisms, including attention, muscle activity, autonomic regulation and behavioural changes. Evidence may demonstrate benefit for particular outcomes without proving that the therapy treats the underlying pathology. A therapy's potential usefulness can therefore depend on the exact condition, treatment protocol, comparator and outcome measured. A systematic review or guideline addressing the specific indication is much more informative than a general claim that the therapy is beneficial.
Complementary medicine should not be confused with replacing necessary conventional treatment. If someone uses an unproven therapy instead of effective treatment for cancer, infection, diabetes, severe asthma or another potentially serious condition, delay can allow disease to progress. NHS guidance specifically advises people to seek medical advice for persistent or recurrent symptoms and not to stop prescribed medicines without discussing this with a doctor.
Complementary approaches can sometimes be incorporated into a conventional care plan when their potential benefits, risks and interactions are understood. The distinction between complementary and alternative therefore has practical safety significance, because using a therapy alongside effective treatment is materially different from using it instead of effective treatment.
Safety assessment should consider both direct and indirect harms. Direct harms can include burns, infections, allergic reactions, organ toxicity, bleeding, drug interactions or injuries associated with particular procedures. Indirect harms include financial cost, false reassurance, unnecessary delay in diagnosis, abandoning effective treatment or becoming dependent on ineffective products. Practitioner regulation also varies considerably.
NHS guidance states that chiropractors and osteopaths must be registered with their statutory regulatory bodies, while some other complementary therapists are not required to be registered by law. For private practitioners, NHS advice recommends checking registration with a professional organisation accredited by the Professional Standards Authority where applicable. Regulatory status therefore provides information about professional oversight but does not itself establish therapeutic effectiveness.
Evidence for complementary medicine can be difficult to interpret because studies may involve heterogeneous treatments, practitioner expertise, treatment intensity, placebo or contextual effects and subjective outcomes. A well-designed trial can determine whether an intervention improves a specified outcome compared with an appropriate control, but a positive result for one protocol does not prove that every version of the therapy works. Conversely, a negative trial does not necessarily establish that every conceivable application is ineffective.
Systematic reviews can synthesise multiple studies, but conclusions depend on the quality and similarity of the evidence. WHO's work on traditional, complementary and integrative medicine emphasises the importance of evaluating safety and efficacy within cultural context and supporting informed choices rather than assuming either universal benefit or universal uselessness.
The appropriate approach to complementary medicine is therefore evidence-informed and safety-conscious. Ask what condition the therapy is intended to treat, what outcome it is claimed to improve, what evidence supports that specific claim, what adverse effects and interactions are known, whether the practitioner is appropriately regulated, what the financial cost is, and whether using it could delay effective diagnosis or treatment. Tell doctors, pharmacists and other relevant healthcare professionals about complementary products or therapies, particularly when prescription medicines are involved.
NHS guidance specifically advises not stopping prescribed medicines without medical advice and recommends professional consultation for persistent symptoms. Complementary medicine can occupy a place alongside conventional care for some people, but the label itself should never be treated as proof of efficacy, safety or suitability.
