Long acting injectables (LAI) have received increased research and commercial interest due to their potential for improving treatment effectiveness and adherence for antipsychotic, antiviral and addiction treatments. A range of materials have been used to formulate LAI products, including lipids and polymers. Classic lipid-based LAI, such as oil solutions of antipsychotic drugs, have been widely prescribed to patients. Clinical evidence has shown significantly improved key therapeutic markers such as reduction of relapses in the case of schizophrenia patients. The commercial LAI products can be given either via subcutaneous or intramuscular injection. The main types of lipid-based LAI formulations include oil solutions, lipid-based nanoparticles and lipid based liquid crystal formulations, which are currently clinically available, and oil suspensions and oleogels and which currently have no commercial products available. This review will discuss all relevant aspects related to the development of lipid-based long acting injectables with a special focus on intramuscular (IM) injectables. It aims to provide useful guidance on effective future LAI product design and development. Lipid-based nanoformulations are not discussed in this review as they are thoroughly reviewed in literature elsewhere.