Self-control problems constitute a potential explanation for the under-investment in preventive health in low-income countries. Behavioral economics offers a tool to solve such problems: commitment devices. We conduct a field experiment to evaluate the effectiveness of different types of theoretically-motivated commitment contracts in increasing preventive doctor visits by hypertensive patients in rural India. Despite achieving high take-up of such contracts in some treatment arms, we find no effects on actual doctor visits or individual health outcomes. A substantial number of individuals pay for commitment but fail to follow through on the doctor visit, losing money without experiencing health benefits. We develop and structurally estimate a pre-specified model of consumer behavior under present bias with varying levels of naivete. The results are consistent with a large share of individuals being partially naive about their own self-control problems: sophisticated enough to demand some commitment, but overly optimistic about whether a given level of commitment is suffciently strong to be effective. The results suggest that commitment devices may in practice be welfare diminishing, at least in some contexts, and serve as a cautionary tale about their role in health care.