**Abstract**

Usage of supplements has increased dramatically this last decade. From herbs to vitamins and mineral, consumers are interested in improving health, selftreatment and preventing diseases. Often using information from the internet to self-prescribe, many consumers believe that natural products are safe, while many others avoid using these products because of the lack of an approval process by health officials in many countries. Herbs and other supplements including proteins, vitamins and minerals provide significant benefits to health. The lack of guidance from health professionals however can be problematic. When combined with drugs and disease, herbs can interact and cause side effects. Some of the steps to evaluate the safe use of supplements is to know their mechanism of action, clinical effect, and consumers' medical history. For example, an herb that induces liver enzymes will reduce the effect of a drug that is metabolized by these same enzymes. This can be life threating if the patient depends on this drug for normal function. Based on drug-herb interaction experience and literature review, this book chapter provides insights into safe use of echinacea, licorice, turmeric, and black seed in patients with heart disease, diabetes, and COVID-19.

**Keywords:** herbs, supplements, drug-herb interaction, safety, COVID-19, heart disease, diabetes
