Many developing countries have recently increased health insurance coverage at a large scale. While it is commonly believed that this has positive effects, to date, it is not well understood through which channels health insurance coverage contributes to the well-being of individuals. More generally, the effects are usually not quantified at the individual level. There are two main reasons for this. First, we lack detailed data on health care utilization and health outcomes, and second, it is not easy to control for selection into insurance. The second problem means that a regression of utilization or outcome measures on insurance coverage will yield biased results and will not estimate the causal effects of health insurance. In this paper, we make progress in both directions. We use rich survey data to evaluate the impact of access to the Peruvian Social Health Insurance called “Seguro Integral de Salud” for individuals outside the formal labor market on a variety of measures for health care utilization, preventive care, health expenditures, and health indicators. We address the second concern by exploiting a fuzzy regression discontinuity design. A household is eligible for the program if a welfare index that is calculated from a number of variables is below a specific threshold. We base our analysis on a natural experiment that is generated by variation in the index around the threshold. We interpret our results through the lens of a simple model. As expected, and in contrast to studies for a number of other countries, we find strong effects of insurance coverage on measures of health care utilization, such as visiting a doctor, receiving medication and medical analysis. The program does not strongly incentivice individuals or health care providers to invest into preventive care. In line with this, in general, we find no effects of insurance coverage on preventive care. The only exceptions to this are our findings that, controlling for selection into insurance coverage, women of fertile age with insurance are more likely to receive pregnancy care and that insured individuals are more likely to be vaccinated. This is in line with the stark decrease in maternal and child mortality that was observed after the program was introduced. As for health care expenditures, we generally find positive effects on the mean and the variability. We complement these findings with quantile treatment effect estimates that show increases at the high end of the distribution. Our interpretation is that insured individuals are encouraged by health care professionals to undertake important treatments and pay for this themselves. At the same time, we find no clear effects on health outcomes at the micro level.