What the FDA labels say about taking them together
Colesevelam and levothyroxine
Colesevelam's FDA label of December 28, 2023 names levothyroxine in its drug interactions section, and levothyroxine's label names colesevelam too. The colesevelam label: “In vivo drug interactions studies showed a decrease in exposure of levothyroxine when coadministered with colesevelam hydrochloride. There have been postmarketing reports of elevated thyroid-stimulating hormone (TSH) in …”
Check it at the source: the colesevelam FDA label on DailyMed (effective December 28, 2023, A-S Medication Solutions); the levothyroxine FDA label on DailyMed (effective February 20, 2024, AbbVie Inc.).
What does the colesevelam label say about levothyroxine?
Colesevelam label, drug interactionsThyroid Hormone Replacement Therapy Clinical Impact: In vivo drug interactions studies showed a decrease in exposure of levothyroxine when coadministered with colesevelam hydrochloride. There have been postmarketing reports of elevated thyroid-stimulating hormone (TSH) in patients receiving thyroid hormone replacement therapy. Intervention: Administer thyroid hormone replacement therapy 4 hours prior to colesevelam hydrochloride.
Source: FDA drug label (COLESEVELAM HYDROCHLORIDE), NDA021176 (Cosette), as published by A-S Medication Solutions, effective December 28, 2023 (SPL set 0127afae-8d8d-43f2-97f9-4f99f6947e81), via openFDA; the full label on DailyMed
What does the levothyroxine label say about colesevelam?
Levothyroxine label, drug interactionsBile Acid Sequestrants (e.g., colesevelam, cholestyramine, colestipol) Ion Exchange Resins (e.g., Kayexalate); Bile acid sequestrants and ion exchange resins are known to decrease levothyroxine absorption. Administer SYNTHROID at least 4 hours prior to these drugs or monitor TSH levels.
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
| Colesevelam | Levothyroxine | |
|---|---|---|
| Labeled for | High cholesterol, Type 2 diabetes | Hypothyroidism |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.262 per tablet 625 mg tablet | $0.0588 per tablet 112 mcg 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