A method and apparatus keeps track of ingestible objects (such as pills or food items) ingested by humans or animals. The objects are supplied with radio frequency identification (RFID) tags encoding data describing the objects. The humans or animals ingesting the objects are equipped with RFID sensors for detecting, decoding, and archiving the data encoded in the tags. A user may scan the body of the human or animal subject with a sensor to determine if a tagged object has been ingested. The tags may be covered with substances or contain elements that dissolve upon entering a digestive system. This allows detection of ingestion and also allows the RFID tag encoding to change in the course of digestion.