Hi Kathy @kathyhg and @boomerexpert. The study I read was preliminary research and the single dose of vitamin D3 would translate to around 100,000 iu only ONCE every 2 or 3 months (= 2.5 mg or 2,500 mcg once every 2 or 3 months).
Safety and any side effects would need to be investigated further, but if it's a single dose taken once every 2 or 3 months it seems the single dose can safely be higher than that (see for example: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4128480/).
You can get doses of 10,000 iu in capsules or tablets online. But you should probably only do this with guidance from a doctor, I think.
Here's some relevant studies:
https://www.ncbi.nlm.nih.gov/pubmed/17463418/
https://www.ncbi.nlm.nih.gov/pubmed/23331510
https://www.ncbi.nlm.nih.gov/pubmed/21419266
https://www.ncbi.nlm.nih.gov/pubmed/21133662
https://www.ncbi.nlm.nih.gov/pubmed/20067648
https://www.ncbi.nlm.nih.gov/pubmed/20557314
https://www.ncbi.nlm.nih.gov/pubmed/22589721
https://www.ncbi.nlm.nih.gov/pubmed/18602003
https://www.ncbi.nlm.nih.gov/pubmed/19748462
After I finish my TB meds I want to try it to help my immune system. I was planning to look into it more then.