Hair supplements are a vast and growing industry. Patients often turn to oral supplements to address hair concerns as they are easily accessible. There are numerous products on the market, many with thousands of reviews (both positive and negative). Nutritional supplements are regulated by the FDA as foods instead of drugs, meaning they do not have to prove their efficacy and safety before becoming available to consumers. While some oral supplements have strong evidence supporting their use for hair growth, many ingredients have not been tested in clinical trials, have only in vitro evidence for hair growth, or have only been tested in animals. Given these industry characteristics, it is important for dermatologists to be aware of the safety and utility of these ingredients to provide appropriate counseling to their patients. The goal of this review is to evaluate the efficacy of popular hair growth oral supplement ingredients and formulations. This review does not address the topical formulations of these ingredients and their effects on hair growth.