I have recently done three fasts: 1. 7 days 2. 19 days; and 3. 13 days I'm going to try another extended fast, starting on Sunday. My main concern is the fact that I take thyroxine for under-active thyroid, 100mg per day. During my last fast (13 days) I had my thyroid function tested at Day 5, and the results indicated: 1. TSH was elevated, at 8.29 (up from 0.09 months prior, with healthy range being: (0.40 - 4.00) 2. Free T4 was at 11.9 (down from 15.1 6 months prior) My levels of TSH were through the roof, while the actual amount of T4 was down. QUESTION: what implications for fasting do these two figures suggest? Not sure what to do about my daily dose: maintain it; taper it throughout long fast; stop it altogether. Has anyone had any relevant EXPERIENCE? I'm strictly looking for someone who: a) has under-active thyroid and understands the above results; and b) has a lot of fasting experience