This study examines how changes in health insurance status affect patients and their care. Results show that, controlling for socioeconomic factors, condition, age, and urgency, patients who lost insurance and patients who changed insurance were more likely to delay seeking care within the four months after visiting an emergency department than people whose health insurance status did not change. Patients who lost coverage were more likely to report no primary care provider and were less likely to have recommended follow-up care within the four-month period. Loss of insurance also was associated with lower likelihood of vaccine use and check-ups in the prior year. The study confirms that a loss or change in health insurance in the prior year has a measurable effect on access to health care. The greatest impact was among patients who lost insurance, though patients who changed health plans also were more likely to delay seeking care than patients whose health insurance status did not change.