The systems and methods described herein can advantageously allow users to discretely measure their exhaled breath in an easy, cost-effective and non-invasive manner. A handheld breath sensing system may be provided with a main housing, a first mouthpiece, a lid, a sampling chamber, a sensor and a microprocessor. The first mouthpiece may be configured to allow a user to exhale into the mouthpiece. The lid may be movable between an open position and a closed position. The sampling chamber may be in fluid communication with the first mouthpiece. The sensor may be in fluid communication with the sampling chamber and configured to measure at least one property of a user's breath. The microprocessor may be configured to process electronic signals from the sensor such that at least one volatile organic compound in the user's breath can be quantified and a resulting biomarker measurement provided to the user in near real-time.
