It cites a study about vitamin D toxicity where the range of cumulative intake causing it was identified to be 2.2 million - 6.3 million IU. When you take 6000 IU daily for a whole year you only reach the lower end of that range, and you definitely shouldn't do that without checking your levels somewhere in between. Taking it for a few months may get you above the recommended blood levels, but is very unlikely to cause issues unless you started with very high levels already (which you most likely did not).

Toxic levels of vitamin D can be life threatening, so do keep your levels in check, but you won't get there unless you really try, so if you can't get out of the bed to have your blood tested just start taking it and check it after 3 months when things get hopefully easier for you. Just make sure to get the number of zeros in the dose right.

Juxtaposing with the quoted passage from the post: “Because vitamin D is potentially toxic, intake of [1000 IU/day] has been avoided even though the weight of evidence shows that the currently accepted [limit] of [2000 IU/day] is too low by at least 5-fold.” --https://www.sciencedirect.com/science/article/pii/S000291652...