Although relatively pain free and taking such a short time to administer but you probably want to also know how long does a botox injection last?. The effective duration of a Botox injection is only about four months. If the patient wants to maintain the same appearance, it is necessary to return for a follow up treatment several times a year. Since Botox injection treatments are not covered by most insurance companies, ongoing treatments might be out of the question for many Botox patients. An alternative long term solution might be traditional plastic surgery.