According to https://www.exaktpak.com/reg_definitions.html serum for cholesterol testing is exempt.
There is a list of category A substances, and another of category B but as I could not find this specific serum listed on either, I searched under "Exempt Human specimen or Exempt Animal Specimen" and found it listed on there.
I'm assuming you are asking this as part of an exam question, in which case please check that you agree with me as I don't want to lead you into failure, but this is the way I see it.
For most items there are identification numbers that need to be added to the packaging, this is the case with many items sent through the mail system.
Even perfume being sent through the post has to carry a special label. This seems to be a fairly new measure so I think it is because of problems in the past and terror threats, that they feel that everything has to be labelled clearly.
