Wearable device, health management system and health management method

A wearable device in a form of a ring configured to be worn on a finger, the wearable device comprising:

• a ring body having a shape of a ring;
• a light emitting element disposed in the ring body, configured to emit a light toward a center side of the ring;
• a first optical element disposed in the ring body closer to the center side of the ring relative to the light emitting element, the first optical element being configured to change a direction of travel of the light to a direction in which a directional angle of the light is narrowed;
• a light receiving element disposed in the ring body, configured to detect a light;
• and
• a second optical element disposed in the ring body closer to the center side of the ring relative to the light receiving element, the second optical element being configured to guide the light emitted by the light emitting element toward the light receiving element,
• wherein the ring body includes a protrusion on an inner peripheral surface of the ring body where the first optical element is disposed, a part of the protrusion being formed to protrude closer to the center side of the ring than another part of the inner peripheral surface where the first optical element is not disposed, and
• wherein the light emitting element and the light receiving element that are adjacent to each other are disposed such that an angle formed between a line segment connecting the center of the ring and the light emitting element and a line segment connecting the center of the ring and the light receiving element is between 55° and 90°.