Anyone care to explain the risks of using this drug?

- I know one must get tested for G6PD deficiency or it may lead to a hemolytic crisis. But I'm unsure how probable one is to have it or how long until this potential problem arises.

- I heard this drug can cause heart attacks in some people, Can this be predicted by a test? Some users on r/covid19 were advising against taking it without doctor supervision in a hospital for this reason but didn't explain nor gave statistics, as usual. The problem was related to prolonged qt intervals