Injection phobia has long been known to interfere with the successful delivery of medical and dental care. Increasingly, as new biological medications administered through regular injection are developed, the inability to self-inject due to anxiety is reducing initiation and adherence to treatment. The prevalence of injection phobia ranges from 7–22% of the general population, while the inability to self-inject may also be increasingly prevalent.Specific phobia — blood, injection, and injury (BII) — is a diagnosis that is characterized by phobic reactions to exposure to injections, injury, or blood, leading to avoidance of such situations, or tolerating these situations only under extreme emotional duress. While the literature on health outcomes related to injection phobia is somewhat limited, injection phobia has been shown to contribute to poor adherence to treatment regimens, or to discontinuance of treatment altogether in diabetes mellitus and multiple sclerosis. Hypotheses about possible psychological and genetic mechanisms have been developed, as well as high psychiatric comorbidities that may contribute to injection anxiety and phobia, or complicate medical treatment. A number of psychological factors, including poor self-efficacy about self-injecting, beliefs about the benefits and risks associated with injecting, and feelings of disgust may contribute to injection phobia. Increased occurrence of vasovagal responses during or following injection may also increase the risk of injection phobia. Because injection phobia can prevent or interfere with the delivery of needed medications, it is believed that injection phobia and self-injection anxiety can have health consequences, however, research in this area is lacking. Cognitive behavioral therapies, including both exposure and cognitive restructuring, have been shown to be an effective treatment.