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 India. Despite achieving high take-up of some contracts, we find no effects on actual doctor visits or health outcomes. A substantial number of individuals pay for commitment, but fail to follow through, losing money without experiencing any health benefit. We develop and structurally estimate a pre-specified model of consumer behavior under present bias with varying degrees of naivete. The results are consistent with a large share of individuals being partially naive: sophisticated enough to demand some commitment, but overly optimistic about whether a given level of commitment is sufficiently strong to be effective.