Your place of employment should have a list of facility-approved abbreviations. Some abbreviations that are used in medical jargon may have more than one meaning (ex.=CV could be either cerebralvascular or cardiovascula; or ALL could be allergies or Acute lymphocytic Leukemia), or may not be approved because it looks too much like something else (ex.= c/o can be mistaken for % when hand written; just as a hand written "u" could look like an "m" or a "0" when writing dosages of insulin, for instance). Almost any medical dictionary will have a list of the common prescription Latin abbreviations (PRN, OS, PO); but be sure and check with your facility first. Even an abbreviation such as BSC (bed side commode) may not be common where you work. My facility does not use the standard TCH (turn, cough,hyperventilate). In documentating, it's important to use the abbreviations that are approved by your facility so that everyone knows what you are talking about; and the abbreviations you use will stand up in a court of law.