The guide is intended for a doctor of any specialty. The reader is invited to start studying medical biochemistry with the selection and medical comprehension of the information from fundamental biochemistry that the doctor needs for practical use in a specific situation with a specific patient. At the same time, this information should provide guidelines for a deep (up to the molecular level) understanding of pathology, taking into account the main biochemical processes, which are better known in theory as pathogenetic mechanisms and are rarely mentioned (although they should certainly be mentioned) in the practice of a doctor.