Flashblood (also called Flushblood) is a technique employed by drug users in which an addict injects himself with blood extracted from another drug user, most commonly one who has injected heroin. After injecting themselves with heroin using a syringe, the user will extract approximately one teaspoon of blood from the vein. Another user will then inject the withdrawn blood into themselves. It is unclear if there is enough heroin in the injected blood to get high or if the high that many users claim is a result of traces of the heroin that had been injected by the user, or if the high is simply the result of the placebo effect.
The Daily Omnivore 