MODERATE — Monitor Closely
🟡 CAUTION — Soy isoflavones inhibit thyroid peroxidase and reduce levothyroxine absorption. Take levothyroxine at least 4 hours before soy products.
Evidence level: STRONG
Soy products can reduce how well your thyroid medication works. Soy interferes with both absorption and thyroid hormone production.
Soy isoflavones (genistein, daidzein) inhibit thyroid peroxidase and reduce levothyroxine absorption in the GI tract. Can reduce levothyroxine efficacy, particularly in iodine-deficient individuals.
Take levothyroxine on an empty stomach at least 1 hour before eating any soy-containing foods. If you consume soy regularly, your thyroid dose may need to be higher. Get TSH checked 6-8 weeks after changing soy intake.
Take levothyroxine first thing in the morning on an empty stomach, 30-60 minutes before food. Take all other supplements and medications at least 4 hours later.
Higher risk for: elderly with cardiac conditions, those with adrenal insufficiency, recent thyroid dose adjustments, concurrent calcium/iron/antacid use (absorption interference), or narrow therapeutic index sensitivity.
Fatigue, weight gain, cold sensitivity, constipation, brain fog — signs that thyroid medication may not be working effectively.
No urgent need to discuss, but always keep your doctor informed of your full supplement and medication list. An up-to-date list helps them make the best treatment decisions.
Thyroid medications are sensitive to absorption interference. Take levothyroxine on an empty stomach, 30-60 minutes before food or other supplements. Space calcium, iron, and antacids at least 4 hours away. Selenium and zinc are generally safe thyroid-supporting nutrients.
Soy products can reduce how well your thyroid medication works. Soy interferes with both absorption and thyroid hormone production.
Take levothyroxine first thing in the morning on an empty stomach, 30-60 minutes before food. Take all other supplements and medications at least 4 hours later.
Fatigue, weight gain, cold sensitivity, constipation, brain fog — signs that thyroid medication may not be working effectively.
Thyroid medications are sensitive to absorption interference. Take levothyroxine on an empty stomach, 30-60 minutes before food or other supplements. Space calcium, iron, and antacids at least 4 hours away. Selenium and zinc are generally safe thyroid-supporting nutrients.
No urgent need to discuss, but always keep your doctor informed of your full supplement and medication list. An up-to-date list helps them make the best treatment decisions.
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