Non-maleficence means to do no harm.

Non-Maleficence: The Ethical Principle of "First, Do No Harm"

When people think about medical ethics, one phrase often comes to mind: "First, do no harm." This timeless expression captures the essence of non-maleficence, one of the four fundamental principles of biomedical ethics. Although the phrase primum non nocere ("first, do no harm") does not appear verbatim in the Hippocratic Oath, it has long been associated with the Hippocratic tradition and continues to serve as a guiding principle in healthcare.

Non-maleficence requires healthcare professionals to avoid causing unnecessary harm to patients. It reminds clinicians that every decision, treatment, and intervention should prioritise patient safety while carefully balancing potential risks and benefits.

What Is Non-Maleficence?

Derived from the Latin non malefacere, meaning "not to do harm," non-maleficence obliges healthcare professionals to avoid actions that may cause injury, suffering, or unnecessary risk. This ethical duty applies not only to doctors but also to nurses, pharmacists, therapists, and all professionals involved in patient care.

Importantly, non-maleficence may sometimes require a healthcare professional to refuse a patient's request if the requested treatment is likely to cause harm or has not been shown to be safe or effective. Ethical practice demands that clinical decisions are based on evidence, sound judgement, and the patient's best interests rather than simply fulfilling every request.

Why Does Non-Maleficence Matter?

Modern medicine offers remarkable treatments that improve and save lives. However, virtually every medical intervention carries some level of risk. Surgery may cure disease but also carries the possibility of complications. Medications relieve symptoms yet may produce unwanted side effects. Even diagnostic tests can expose patients to discomfort, anxiety, or radiation.

The principle of non-maleficence encourages healthcare professionals to ask important questions before proceeding:

Will this intervention cause unnecessary harm?
Do the expected benefits outweigh the risks?
Is there a safer alternative?
Has the patient been fully informed about potential complications?

By carefully considering these questions, clinicians strive to provide care that maximises benefit while minimising harm.

Non-Maleficence in Everyday Clinical Practice

The principle is reflected in countless everyday decisions within healthcare.

For example, a doctor may discontinue a medication that is known or believed to be harmful, or refuse to prescribe a treatment that lacks evidence of effectiveness. Although a patient may request a particular medication, healthcare professionals have an ethical responsibility to avoid interventions that are unlikely to help and may instead expose patients to unnecessary risk.

Other examples include:

Confirming a patient's identity before administering medication to prevent medical errors.
Prescribing antibiotics only when clinically indicated to reduce adverse effects and antimicrobial resistance.
Using the lowest effective dose of radiation during imaging procedures.
Following strict infection prevention and control measures to reduce healthcare-associated infections.
Ensuring patients understand the risks and benefits of treatment before obtaining informed consent.

These routine practices demonstrate that preventing harm is just as important as treating illness.

Non-Maleficence in Public Health

The principle also plays a vital role in public health, where decisions often involve balancing small harms to individuals against much greater benefits for society.

A familiar example is legislation banning smoking in public places. While such restrictions may inconvenience smokers, they protect others from exposure to second-hand smoke and help discourage smoking across the wider population, leading to significant improvements in public health.

Childhood vaccination provides another important example. Administering a vaccine may cause temporary pain or distress, particularly in infants and young children. Like all medical interventions, vaccines also carry a very small risk of adverse reactions. However, they provide highly effective protection against potentially life-threatening infectious diseases. For both healthcare professionals and most patients, the overwhelming evidence shows that the benefits of vaccination far outweigh the temporary discomfort of the injection or the rare possibility of serious side effects.

These examples illustrate that non-maleficence does not always mean avoiding all harm. Rather, it requires ensuring that any harm is minimised and justified by a substantially greater benefit.

When Harm Cannot Be Completely Avoided

Healthcare professionals frequently encounter situations where some degree of harm is unavoidable.

Chemotherapy, for example, can cause nausea, fatigue, hair loss, and other serious side effects. Nevertheless, it may offer the best opportunity to treat cancer or prolong survival. Similarly, major surgery inevitably involves pain, recovery, and the risk of complications, yet it may prevent severe disability or save a patient's life.

In these circumstances, non-maleficence does not prohibit treatment. Instead, it requires clinicians to ensure that the expected benefits significantly outweigh the potential harms and that every reasonable measure is taken to minimise risk.

Balancing Non-Maleficence with Other Ethical Principles

Non-maleficence is one of the four widely recognised principles of biomedical ethics:

Autonomy – respecting a patient's right to make informed decisions.
Beneficence – acting in the patient's best interests.
Non-maleficence – avoiding unnecessary harm.
Justice – ensuring fairness in the distribution of healthcare resources.

These principles do not always align perfectly. Healthcare professionals often face ethical dilemmas where competing principles must be balanced.

For instance, a patient may request a treatment that lacks scientific evidence or carries significant risks. While respecting patient autonomy is important, clinicians also have an ethical duty to avoid causing harm. Likewise, many beneficial medications have serious side effects, requiring doctors and patients to carefully weigh the potential risks against the anticipated benefits before treatment begins.

Shared decision-making is central to resolving these dilemmas. Once healthcare professionals have explained the available evidence, possible risks, expected benefits, and alternative options, patients can make informed choices about their care. In this way, non-maleficence works alongside autonomy and beneficence to support ethical, patient-centred practice.

The Continuing Importance of Non-Maleficence

Advances in medical technology, artificial intelligence, precision medicine, and genetic testing have created new ethical challenges. Healthcare professionals must now consider not only physical harm but also psychological, social, and digital harms, including issues such as data privacy, algorithmic bias, and equitable access to healthcare.

Despite these advances, the principle of non-maleficence remains as relevant today as it was centuries ago. Patients place enormous trust in healthcare professionals, expecting that every decision will be guided by competence, compassion, and a commitment to their well-being.

Ultimately, non-maleficence is more than simply avoiding mistakes. It is a commitment to thoughtful, evidence-based, and patient-centred care. It reminds healthcare professionals to continually ask: How can we provide the greatest benefit while causing the least possible harm?

As medicine continues to evolve, this enduring ethical principle will remain fundamental to safe, compassionate, and responsible healthcare, ensuring that every clinical decision reflects the profession's commitment to protecting those entrusted to its care.