Background: Patients respond to medications differently because of variations in the genes that determine medication exposure and medication response. Objective: The aim of this review is to introduce pharmacogenomic testing and explain how to start using pharmacogenomic tests in general practice. Discussion: Knowledge of the variants in pharmacogenomics is useful when prescribing a variety of medications. International guidelines have identified at least 15 genes for which testing can inform the prescribing of 30 different medications with good evidence of clinical benefit. Nonetheless, pharmacogenomic tests should not be used as the sole basis for prescribing decisions, and should be considered in the context of other relevant clinical and laboratory features. General practitioners can incorporate pharmacogenomic tests into their clinical practice for patients with medication-related problems or those who are likely to require medications for which pharmacogenomics can provide guidance.