What the FDA labels say about taking them together
Dexamethasone and levothyroxine
Dexamethasone's FDA label (Hemady) of January 9, 2026 names levothyroxine in its warnings and precautions section, and levothyroxine's label names dexamethasone too. The levothyroxine label: “Glucocorticoids Short-term administration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels.”
Check it at the source: the dexamethasone FDA label on DailyMed (effective June 6, 2025, Hikma Pharmaceuticals USA, Inc.); the levothyroxine FDA label on DailyMed (effective February 20, 2024, AbbVie Inc.).
What does the dexamethasone label say about levothyroxine?
Hemady label (Edenbridge Pharmaceuticals LLC., January 9, 2026), warnings and precautionsWhen concomitant administration of corticosteroids and levothyroxine is required, administration of corticosteroid should precede the initiation of levothyroxine therapy to avoid adrenal crisis.
Source: FDA drug label (Hemady, NDA211379), Edenbridge Pharmaceuticals LLC., effective January 9, 2026 (SPL set 6b9cf32c-6d60-4853-bbfd-2304ffc2c129), via openFDA
Source: FDA drug label (Dexamethasone Intensol), Hikma Pharmaceuticals USA, Inc., effective June 6, 2025 (SPL set b15200fb-1826-472b-a907-e677a272513b), via openFDA; the full label on DailyMed
What does the levothyroxine label say about dexamethasone?
Levothyroxine label, drug interactionsGlucocorticoids (e.g., Dexamethasone > 4 mg/day) Short-term administration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels.
Levothyroxine Sodium label (Amneal Pharmaceuticals NY LLC, December 6, 2024), drug interactionsDrug or Drug Class: Amiodarone Beta-adrenergic antagonists - (e.g., Propranolol > 160 mg/day) Glucocorticoids -(e.g., Dexamethasone ≥ 4 mg/day) Propylthiouracil (PTU); Effect: Administration of these enzyme inhibitors decrease the peripheral conversion of T 4 to T 3, leading to decreased T 3 levels. However, serum T 4 levels are usually normal but may occasionally be slightly increased. In patients treated with large doses of propranolol ( > 160 mg/day), T 3 and T 4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. …
Levothyroxine Sodium label (Bryant Ranch Prepack, July 29, 2025), drug interactionsGlucocorticoids (e.g., Dexamethasone greater than or equal to 4 mg/day); Short-term administration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels. However, long-term glucocorticoid therapy may result in slightly decreased T3 and T4 levels due to decreased TBG production (See above).
Source: FDA drug label (Levothyroxine Sodium, NDA021210), Amneal Pharmaceuticals NY LLC, effective December 6, 2024 (SPL set fca88c97-5cd4-4834-ba87-deb5bd637788), via openFDA
Source: FDA drug label (Levothyroxine Sodium, NDA021116), Bryant Ranch Prepack, effective July 29, 2025 (SPL set 9e3bffb9-f66e-4c73-befc-e60d769f6610), via openFDA
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
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
| Dexamethasone | Levothyroxine | |
|---|---|---|
| Labeled for | Asthma, Eczema (atopic dermatitis), Leukemia, lymphoma and myeloma, Herpes and shingles, Crohn's disease and ulcerative colitis, Multiple sclerosis, Osteoarthritis, Rheumatoid arthritis, Psoriasis, Allergies, Anemia, Pain | Hypothyroidism |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.193 per tablet 4 mg tablet | $0.0588 per tablet 112 mcg tablet |
| Shortage now | In shortage | 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