Intermittent fasting and your thyroid: what to keep in mind
If you have hypothyroidism or other thyroid issues, fasting takes more care. What to watch for and when to check in with your doctor.
Part of the complete guide Intermittent fasting and health: side effects, precautions and special cases
An important note first
If you have a thyroid condition (hypothyroidism, Hashimoto's, and so on), talk to your doctor before you start fasting. This guide is informational and doesn't replace medical advice. Every thyroid is its own story.
How fasting and your thyroid interact
Your thyroid regulates your metabolism and is sensitive to "low energy" signals. Very aggressive fasts stacked on a steep deficit can, in sensitive people, lower the conversion of thyroid hormone (T4 to T3). It doesn't happen to everyone, but it's worth not overdoing it.
Thyroid medication and fasting
Levothyroxine is normally taken on an empty stomach, 30-60 minutes before eating or drinking coffee. That fits well with intermittent fasting: take it in the morning with water and stick to your window. Never change your regimen without your doctor.
Practical recommendations
- Start gentle (12/12, 14/10), don't jump to 20/4.
- Don't stack fasting on an aggressive calorie deficit.
- Prioritize protein and micronutrients (iodine, selenium, zinc from food).
- Watch for signs: extreme fatigue, feeling cold, hair shedding, low mood.
How Ayúname helps
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