If I draw a molecule (for example glucose) and I want to name it, should I write glucose or Glucose? My aim is to draw a molecule, add the name below and then use this as a figure in a Word text.
Stay with the rules set by IUPAC's colour books, e.g. Blue Book for organic compounds, and Red Book for inorganic compound, and and don't capitalize the names if these names are used within an English phrase. Descriptors like (E/Z) you always capitalize are a different thing, though.
If these documents are too long for you, you may consider their condensed versions (cf. chemistry.se resources page about material to learn chemistry, section nomenclature) for their brief guide and 4-page excerpts (guide, excerpt for organic; guide, excerpt for inorganic compounds). Below the heading of the 4-page excerpts for both (which are published open access):