Hey Mike,
Vitamin D3 is not a monotherapy. To be effective in preventing CH it needs all the cofactors illustated in the following photo of what I take and suggest to other CHers.
You can find the published treatment protocol at VitaminDWiki at the following link.
http://www.vitamindwiki.com/tiki-download_wiki_attachment.php?attId=7708
Readers of my webpage at VitaminDWiki have downloaded 61,671 copies of the anti-inflammatory regimen CH and MH preventative treatment protocol since I posted it on 21 Jan 2017. Dr. Mark Burish, MD, PhD, Director, Will Erwin Headache Research Center, UT Houston, thought enough of this CH preventative treatment protocol and the medical evidence from the online survey of CHers taking the anti-inflammatory regimen to control their CH for the last 9 years, to publish an RCT on clinicaltrials.gov based on this treatment protocol.
https://www.clinicaltrials.gov/ct2/show/NCT04570475?sfpd_s=09%2F30%2F2020&sfpd_d=14
If you have any further questions about this regimen, please shoot me a PM
Take care and hang in there.
V/R, Batch