UC San Diego researchers reported a battery-free fingertip sweat patch that continuously monitors levodopa medication levels in people with Parkinson’s disease, with sweat-based measurements reportedly comparable to standard laboratory blood tests. The work, published in PNAS, describes continuous pharmacodynamic tracking without patient power requirements. The approach targets a clinical gap: levodopa dosing precision worsens as patients progress, while diaries and infrequent blood testing can miss timing gaps between doses. The patch uses chemical sensing in sweat to infer medication exposure in real time. Continuous monitoring could enable tighter personalized dosing schedules and inform future closed-loop systems to adjust therapy at home. It also introduces a practical pathway for translating lab-grade pharmacokinetic measurements into more frequent, low-friction data capture. If adopted, the technology could reshape how clinicians adjust levodopa regimens and how trials evaluate adherence and exposure-response relationships.