Is it a sin for a Catholic to stop chemotherapy?

Not in itself. The teaching here is more open than most people expect.

Catholic teaching sorts treatments into two groups. Proportionate means offer a reasonable hope of benefit. They also do not bring an excessive burden or cost. A person has a duty to use them. Disproportionate means are the other case. They offer no reasonable hope of benefit, or they do bring an excessive burden or cost. The Ethical and Religious Directives say plainly that "a person may forgo extraordinary/disproportionate means of preserving life."

The seventh edition was approved by the US bishops in November 2025. It is clear about who decides. The call "belongs to the patient (or the patient's surrogate)," and it "should be informed by professional medical advice." What is being judged is "what constitutes a proportionate benefit and what constitutes an excessive burden."

Cost is a fair part of that. The Directives name excessive expense on the patient, the family, or the community.

John Paul II spoke to the fear behind this question. He did so in Evangelium vitae, his 1995 encyclical. To forgo extraordinary or disproportionate means, he wrote, "is not the equivalent of suicide or euthanasia." Rather, it "expresses acceptance of the human condition in the face of death."

Whether a treatment is proportionate for you is a decision for you and your care team. A hospital ethics consultation can help.

Sources

• USCCB — Ethical and Religious Directives for Catholic Health Care Services, Seventh Edition (2025)
• John Paul II — Evangelium vitae, no. 65
• National Cancer Institute — Choices for Cancer Care When Treatment May Not Be an Option
• MedlinePlus — Advance Directives