What the FDA labels say about taking them together
Levothyroxine and thyroid
Thyroid's FDA label of November 15, 2023 names levothyroxine in its drug interactions (prescription label) section; the levothyroxine labels PlainMeds reads (4) do not name thyroid. The thyroid label: “In a patient with a nonfunctioning thyroid gland who is receiving thyroid replacement therapy, free levothyroxine may be decreased when estrogens are started thus increasing thyroid requirements.”
Check it at the source: the levothyroxine FDA label on DailyMed (effective February 20, 2024, AbbVie Inc.); the thyroid FDA label on DailyMed (effective November 15, 2023).
What does the levothyroxine label say about thyroid?
Levothyroxine's label (effective February 20, 2024) and its 3 other brand-application labels do not name thyroid in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Synthroid), AbbVie Inc., effective February 20, 2024 (SPL set 1e11ad30-1041-4520-10b0-8f9d30d30fcc), via openFDA; the full label on DailyMed
What does the thyroid label say about levothyroxine?
Thyroid label, drug interactions (prescription label)In a patient with a nonfunctioning thyroid gland who is receiving thyroid replacement therapy, free levothyroxine may be decreased when estrogens are started thus increasing thyroid requirements.
Source: FDA drug label (Thyroidinum), Boiron, effective November 15, 2023 (SPL set 86335e4b-a2f8-6143-e053-2a91aa0a29c6), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Levothyroxine | Thyroid | |
|---|---|---|
| Labeled for | Hypothyroidism | n/a |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.0588 per tablet 112 mcg tablet | $1.20 per tablet 120 mg tablet |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once