Multivitamins should be taken well separated in time from the administration of dolutegravir (minimum 2 hours after or 6 hours before). Factors that decrease dolutegravir exposure should be avoided in the presence of integrase class resistance. This includes co-administration with medicinal products that reduce dolutegravir exposure (e.g. mutivitamins).
Tivicay Summary of Product Characteristics, ViiV Healthcare, March 2019. 

Simultaneous coadministration of a multivitamin preparation (One-A-Day) and dolutegravir (50 mg once daily) to 16 subjects decreased dolutegravir Cmax, AUC and Ctrough by 35%, 33% and 32%, respectively. Dolutegravir should be administered 2 hours before or 6 hours after taking medications containing polyvalent cations.
Tivicay US Prescribing Information, ViiV Healthcare, July 2019.

Coadministration of a multivitamin preparation with high metal divalent cation content (One-A-Day, single dose) and dolutegravir (50 mg, single dose) was studied in 16 HIV-negative subjects and was found to decrease dolutegravir AUC, Cmax and Ctrough by 33%, 35% and 32%, respectively. 

Pharmacokinetics of the HIV integrase inhibitor S/GSK1349572 co-administered with acid-reducing agents and multivitamins in healthy volunteers. Patel P, Song, I, Borland J, et al. J Antimicrob Chemother, 2011, 66: 1567-1572.