Either Trump is taking hydroxychloroquine, a potentially risky drug, or he's irresponsibly lying about it - 2020-05-18
Hydroxychloroquine is an anti-malarial drug that a non-randomized study from a French lab, publicized in March, initially suggested could be used as a treatment in fighting the coronavirus. In March, Trump frequently touted the drug, calling it "one of the biggest game changers in the history of medicine." But further studies have concluded that it is not effective in many cases and should not be routinely used to treat patients.
Trump seems to be taking it not as a treatment for Covid-19 — he's apparently tested negative — but as a preventative to protect himself from contracting it. There's no medical evidence supporting the idea that this would work, and the risk of potential psychiatric and cardiac side effects, which are serious, would likely strongly outweigh any (hypothetical) benefits.
Nevertheless, Trump claims to be taking the drug anyway.