score:2
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.
Upvote:1
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.
Upvote:2
Normal multivitamins are not a problem to bring to China and there is no need to declare them, just make sure they are in original packing to avoid confusion if bag get checked.
There are no legal requirements what so ever so declare vitamins.
Take the amount you need and as long as the amount is reasonable for the duration of your stay you will be fine.