Everything that is our existence--us, our bodies, and everything in, above, and all around us, is made up of "chemicals." Everything is made of chemical elements, including our eyes, our hearts, our brains, our bones and our blood. We breathe chemicals with each breath--one of them required, many others not.
Chemistry is the study of these chemical elements, and how they react with one another, how they combine and form compounds, how they can be manipulated, and how they can benefit humanity.
Biology involves activity within and between organisms--anything that is alive. This exclusively involves anything that was born into existence by parent organisms, had to secure nourishment to survive, attempted to reproduce, and passed away. It is not separate from chemistry, in that biology primarily involves the study of chemical reactions within and between organisms.
Why is this relevant to us today? Because modern medicine is pharmacologically-based. This means that modern physicians are using synthetic chemical compounds and the chemical reactions they generate, to deal with challenges to a patient's biological health.
The issue to note here is that biology involves chemistry, but chemistry does not involve biology. This means that chemical reactions are irrespective of whether or not elements are Biologically Compatible. Biological Compatibility specifically involves the health of an organism, and its ability to live at full capacity. Where compatible elements support an organism's capacity to remain alive and fully functional, Biologically Incompatible elements hinder, reduce or significantly restrict an organism's ability to remain alive and fully functional.
Modern Medicine does not respect Biological Compatibility, in that elements are used to support patient health, irrespective of any Biological Incompatibilities. The biochemistry of the body is not compatible with the chemistry of pharmaceutical compounds, thus calling for warnings of side effects.
This compromise may be acceptable in emergencies, but it is counter productive in the realm of Restorative and Preventive Healthcare.