https://communityoperatingsystem.wordpress.com/2020/06/20/is-folic-acid-an-effective-treatment-for-covid-19/

tl;dr: one of the HCQ trials use folate tablets as the placebo... Which is a real WTF: why would you use something that potentially has a benefit rather than a true placebo with no active ingredients? Purpose-made placebo tablets are widely available.