The Hippocratic Oath is the oldest and most famous ethical code in medicine, a pledge that defines a physician’s moral responsibilities to patients, teachers, and the profession. Written sometime between the fourth and fifth century BC, it originated in ancient Greece and has shaped medical ethics for over two thousand years. Most medical school graduates still recite some version of it today, though the words they speak are quite different from the original.
Origins of the Oath
No one knows exactly who wrote it. Hippocrates himself was an Attic citizen born on the island of Cos, likely the heir of well-to-do merchants or artisans rather than an aristocrat. The text was probably composed not by Hippocrates personally but by a follower or learned scribe, possibly from the school of Pythagoras. Regardless of its true author, the oath became the first formal definition of the medical profession: a covenant binding teachers, colleagues, and students of the healing arts to a shared set of principles.
What the Original Oath Says
The original oath covers several distinct commitments. The first is a deep loyalty to one’s teachers. Physicians swore to hold their instructor “as equal to my parents” and to share medical knowledge only with those who had formally signed the covenant and taken the oath. Medicine, in other words, was treated as a sacred tradition passed within a professional lineage.
The ethical core of the oath focuses on patient welfare. Physicians pledged to offer “all my attention, my science and my love” to those who suffer, never betraying a patient or risking their well-being out of vanity. The oath also contains an early version of patient confidentiality: anything seen or heard during treatment, “which on no account one must spread abroad, I will keep to myself, holding such things shameful to be spoken about.” And it explicitly commits the physician to treating anyone in need, “prince or slave,” regardless of social standing.
Perhaps most controversially, the original oath includes outright prohibitions. Physicians swore not to perform surgery if they lacked the skill, not to provide any substance that could cause an abortion, and not to give a patient a remedy that might “take away his breath,” even if the patient begged for it in anguish. These bans on abortion, euthanasia, and surgery by unqualified practitioners are the clauses that have been most heavily revised or dropped in modern versions.
“First, Do No Harm” Is Not in the Oath
One of the most common misconceptions about the Hippocratic Oath is that it contains the phrase “first, do no harm.” It doesn’t. According to Harvard Health Publishing, that phrase comes from a separate Hippocratic text called “Of the Epidemics.” The original oath does express the spirit of avoiding harm, stating that the physician will “never harm my suffering friend, because life is sacred,” but the famous Latin phrase “primum non nocere” appears nowhere in the oath itself.
How the Modern Oath Differs
Very few medical schools use the ancient Greek version today. The most widely adopted modern alternative was written in 1964 by Louis Lasagna, then the academic dean of Tufts University School of Medicine. His version keeps the ethical heart of the original but updates the language and drops the more controversial prohibitions. It makes no mention of abortion or surgery restrictions. Instead, it emphasizes that physicians “remain a member of society, with special obligations to all my fellow human beings, those sound of mind and body as well as the infirm.”
Lasagna’s version also introduces a more personal, humanistic tone. It closes with the hope that the physician will “long experience the joy of healing those who seek my help,” a line that reflects a shift from the original’s solemn religious gravity toward something warmer and more aspirational.
The Declaration of Geneva
Alongside Lasagna’s oath, the other major modern successor is the Declaration of Geneva, adopted by the World Medical Association in 1948, just three years after the end of World War II. That timing was not accidental. The atrocities committed by physicians in Nazi concentration camps made the need for a renewed ethical framework urgent and undeniable.
The Declaration builds directly on Hippocratic principles but frames them in the language of international human rights. It has been carefully revised only a handful of times over many decades, deliberately kept stable to avoid being influenced by passing trends. The World Medical Association considers it the modern version of the Hippocratic Oath, though it’s designed to be read alongside more detailed policies like the International Code of Medical Ethics, which was adopted the same year.
Why It Still Matters
The Hippocratic Oath has no legal force. No physician can lose their license for breaking it, and no court enforces its provisions. Its power is entirely symbolic and cultural. It functions as a rite of passage, marking the moment a medical student formally accepts the responsibilities of the profession. That ritual carries real weight: studies consistently find that most medical schools in the United States and many other countries include some form of oath ceremony at graduation.
What makes the oath enduring is not any single clause but the underlying framework it established. The idea that physicians owe a duty of care to every patient, that patient secrets must be protected, that medical knowledge comes with moral obligations, and that the physician’s ego and ambition must never come before a patient’s welfare. These principles, first articulated on a Greek island roughly 2,400 years ago, remain the foundation of medical ethics today. The specific words have changed. The core commitments have not.