Continuous molecular monitoring could improve care because most clinical decisions rely on lab tests, yet outside glucose and blood oxygen, monitoring still depends on infrequent blood or urine samples that provide only isolated time points. This is especially limiting for drugs like vancomycin, which has a narrow therapeutic window and large patient-to-patient variability. To address this, we are developing wearable patches with electrochemical aptamer-based (EAB) sensors on small solid needles for continuous, real-time vancomycin measurement. These sensors use a target-binding aptamer attached to an electrode and tagged with a redox reporter such as methylene blue; target binding changes aptamer conformation, generating an electrochemical signal. In a pilot clinical trial in healthy volunteers, fully self-contained EAB patches continuously measured vancomycin in dermal interstitial fluid every 5 minutes over 24 hours. Signals were consistent across patch locations and participants, and pharmacokinetic modeling revealed drug distribution and clearance dynamics missed by standard infrequent sampling.