Colorado has approved a proposition to allow terminally ill people to end their own lives.

The law requires that a mentally competent patient have a six-month prognosis and get two doctors to approve requests for life-ending medication.

It requires doctors to discuss alternatives with the patient as well as safe storage, tracking and disposal of lethal drugs, recognizing that a patient can change his or her mind.

Colorado becomes the fifth state to allow medically assisted suicide, joining Oregon, Washington, Vermont and California. Montana’s state Supreme Court has ruled that doctors can use a patient’s request for life-ending medication as a defense against any criminal charges linked to the death.

Opponents argued that the proposal would facilitate doctor-assisted suicide, especially after mistaken terminal diagnoses.