I'll let others comment on the legal/regulation side (which can be tricky to find when it comes to China), but in practice I went through the Chinese customs with over 100 vitamin pills (from Hong Kong to Shenzhen) in December 2018: nobody asked me anything, I wasn't asked to show them to anyone, and I haven't seen any information about me having to declare them.
As always with medication you can take or leave, I would advice to leave behind.
If you do not have pills on you, there is no chance on a problem with confusion and hard to explain because of language problems.
If you can take a container, bought with those pills in and with the chemical names on it, I would not doubt as much. But do not take more than you would expect to use in the length of a short visit or for the first few weeks of a long visit.