In the past few decades, drug metabolism research has played an ever increasing role in the design of drugs, and medicinal chemists have developed general principles for reducing compound metabolism. While several authors have reviewed techniques for reducing metabolism, there is no review that summarizes different approaches to improving the metabolic stability of heterocycles. In this review, we summarize examples where changes were made at or near the heterocycle to improve metabolic stability, hoping to provide a useful guide to medicinal chemists. The majority of the examples included came from searching the online open access database CHEMBL, papers that cite leading reviews in the drug metabolism field, and recent reviews on drug metabolism. The main criteria for selecting examples was that the change made to improve metabolism had to occur at or near the heterocycle and nowhere else on the molecule. Data predominantly came from in vitro microsomal stability studies, with some from bioactivation studies and in vivo PK studies. The review is organized by first discussing saturated heterocycles (organized by ring size) and then heteroaromatic compounds.