How to fast without getting a migraine

Every time I fast I get a migraine starting on the 2nd day and then the migraine lasts 3 days. I'm thinking I have hypgoglycemia and it is causing the migraines, however I've never had a doctor tell me. I eat fairly clean, no sugar, no wheat, I don't eat out and no alcohol. I have a bad thyroid and wish to fast but I can't get past day 2. I would also love to do a Liver Flush but am afraid to not eat. Any suggestions appreciated!

Thanks!
Cheryl Tweet