Hello Thank you for trusting HCM Dear probably it won t cause dark spots until unless you developed iron deficiency or be complex deficiency or Addison, so disease, or polyposis colon, Cushing syndrome etc.. But still until unless examination it is difficult to say what it is. Some macroglossia, seizures(side effect) may cause tongue bite look like dark spots. Please consult your doctor he will examine and treat you accordingly. I think I answered to your question if you have more questions please feel free to ask me. Take care