Drug delivery is the process of administering a pharmaceutical compound into the body through various routes to achieve a therapeutic effect. Oral, injection-based, transdermal, and carrier-based are some of the types of drug delivery devices. Injectable drug delivery facilitates the rapid transport of a drug into the body by bypassing first-pass metabolism. It also helps in administering drugs in unconscious and comatose patients. Injectable drug delivery is used in conditions such as hormonal imbalance, cystic fibrosis, autoimmune diseases, pain, Wilson's disease, hemophilia, hepatitis C, and ribose-5-phosphate isomerase deficiency. Toxicity due to incorrect dosing, invasive, and sterility are some of the disadvantages of injectable drug delivery systems. Injectable drug delivery technologies are categorized into device technologies and formulation technologies. Injectable drug delivery device technologies are further categorized into conventional injection devices, self-injection devices such as injectors and pen injectors, and others such as micro-needle, blunt needle, and nano-needle injections. On the other hand, injectable drug delivery formulations are further categorized into novel drug delivery formulation and conventional drug delivery formulation.