Last updated: April 25, 2026
Who Supplies Levothyroxine (SYNTHROID) to the Market?
SYNTHROID is the brand name for levothyroxine sodium, a synthetic thyroid hormone API. The supply chain for SYNTHROID in the US market typically includes (1) upstream API manufacturers supplying levothyroxine sodium and (2) finished-dose manufacturers and packagers that produce tablets and manage labeling, distribution, and market-specific packaging.
Because “SYNTHROID” is a branded product, supplier identification in practice hinges on two public pillars: (a) ANDA/505(j) and 505(b)(2) filings that list drug substance manufacturers and (b) the FDA’s listing and approval records tied to each application strength and dosage form. Without access to those application-level and label-level records for the exact market, product strength, and package configuration, “suppliers” cannot be mapped to a definitive list with audit-grade specificity.
What counts as a “supplier” for SYNTHROID?
For business decisions, the only supplier categories that matter are these:
- Drug substance (levothyroxine sodium) manufacturers: produce the API used in tablets.
- Finished-dose (tablet) manufacturers/packagers: compress/coat/formulate, package, and label product for sale.
What controls supplier visibility?
Supplier names in public sources usually appear under:
- FDA approval and application dossiers (for branded manufacturing and for generic/authorized products that disclose listed drug substance and manufacturing sites).
- FDA Drug Establishment Registration and Listing (DRLS): identifies registered establishments for drugs, but does not automatically connect an individual site to “SYNTHROID” specifically without application-to-site mapping.
- FDA Orange Book: confirms the listed drug and product entries, but it does not provide a full, direct “supplier list” for the brand.
What can be stated from public FDA frameworks
What the FDA records can confirm at a high level
Levothyroxine sodium is a widely manufactured drug substance with multiple registered manufacturing establishments in the US under FDA DRLS. Finished-dose levothyroxine products are also manufactured by multiple establishments, depending on the label, marketing authorization, and package configuration. FDA-maintained drug and establishment databases provide the structural path to identifying the relevant establishments, but they do not yield a single authoritative “SYNTHROID supplier roster” without application-level linkage.
Why ANDA and 505(b)(2) disclosures matter
When generics or 505(b)(2) products reference levothyroxine sodium, their submission components often disclose the drug substance manufacturer(s) and the drug product manufacturer(s). Those disclosures can be mapped to the supply base feeding the levothyroxine market segment. For SYNTHROID specifically, the same mapping logic must be applied to the brand’s application history and manufacturing site details.
Operationally useful supplier map (how to structure the search)
Even when the final list must be built from application-to-site mapping, you can structure the supplier map for levothyroxine as follows.
Supplier matrix for SYNTHROID (buildable categories)
| Supply chain node |
Supplier type |
Data needed to finalize names |
| Upstream |
Levothyroxine sodium API manufacturer |
Application disclosure or label-level manufacturing site for the brand |
| Midstream |
Tablet manufacturing site |
Manufacturing site tied to the specific dosage strength and NDC |
| Downstream |
Packaging and release sites |
Packager/labeler tied to NDC and commercial pack configuration |
Typical constraints that change “who supplies SYNTHROID”
- Strength-dependent manufacturing: the same brand can be manufactured in different strengths at different sites.
- NDC/package dependent labeling: different presentation configurations can route through different packaging and distribution workflows.
- Lifecycle changes: manufacturing sites can change over time with FDA supplements and cGMP updates.
Key Takeaways
- SYNTHROID’s supply chain has two essential “supplier” layers: levothyroxine sodium API manufacturers and finished-dose tablet manufacturing/packaging sites.
- Public FDA databases provide establishment coverage and listing frameworks, but they do not automatically produce a single authoritative, brand-specific supplier list without application-to-site linkage for each NDC/strength.
- The audit-grade method to identify SYNTHROID suppliers is to map FDA application manufacturing site disclosures to brand product entries at the strength and NDC level.
FAQs
1) What is SYNTHROID’s active ingredient from a supplier perspective?
SYNTHROID is levothyroxine sodium (thyroid hormone) in tablet form, supplied to manufacturers as an API and then formulated into finished-dose tablets.
2) Are SYNTHROID suppliers the same as levothyroxine generic suppliers?
Not necessarily. Levothyroxine generics can use different API and tablet manufacturing sites than the branded product, even when the API is chemically identical.
3) Where are supplier names typically recorded for branded drugs?
Supplier/manufacturing site identifiers are recorded in FDA application documentation and reflected in establishment registrations, with the most precise mapping requiring application-to-site and product-to-NDC linkage.
4) Do supplier sites vary by strength or NDC for SYNTHROID?
They can. Different dosage strengths and package configurations often route through different manufacturing and packaging operations depending on commercial and regulatory history.
5) Can FDA listing alone provide a definitive list of SYNTHROID suppliers?
FDA DRLS and Orange Book provide structure, but definitive “who supplies SYNTHROID” requires connecting the brand’s product entries to the specific manufacturing sites documented in regulatory submissions.
References (APA)
[1] U.S. Food and Drug Administration. (n.d.). Drug Establishment Registration and Drug Listing (DRLS). FDA. https://www.accessdata.fda.gov/scripts/cder/drls/
[2] U.S. Food and Drug Administration. (n.d.). Drugs@FDA. FDA. https://www.accessdata.fda.gov/scripts/cder/daf/
[3] U.S. Food and Drug Administration. (n.d.). FDA Orange Book: Approved Drug Products with Therapeutic Equivalence Evaluations. FDA. https://www.accessdata.fda.gov/scripts/cder/ob/
