Does Synthroid contain wheat or gluten as an excipient?

We cross-check each Synthroid product label against four data sources: DailyMed (FDA Structured Product Labels), the European Medicines Agency centrally-authorised medicines database, the Plogsted curated gluten-free drug list, and the 2024 Mangione et al. pediatric pharmacy NDC analysis. Inactive ingredients are scanned against a 146-entry red-flag dictionary covering wheat, barley, rye, malt, source-ambiguous starches, and FDA gluten-free attestation phrases. Mostly yes — but worth a quick call to the manufacturer for some generics. Of 15 product labels we checked, 10 are clean, 2 are confirmed gluten-free by the maker, and 3 contain an inactive ingredient (typically a source-ambiguous starch) whose botanical origin isn't fully disclosed. None contained confirmed gluten.

Can different manufacturers' generic versions of Synthroid have different gluten status?

Yes. Generics in the United States must use the same active ingredient as the brand, but they are not required to use the same inactive ingredients. Two generics of Synthroid from different manufacturers can use entirely different starch sources, binders, and fillers. A pharmacy may also switch which manufacturer it dispenses between fills without notifying you. Each manufacturer-specific entry below corresponds to a separately-filed product label.

DailyMed checked live · reference data updated May 17, 2026 · 15 product labels screened

Is Synthroid gluten-free?

Looks mostly clean — worth verifying with the maker. Mostly yes — but worth a quick call to the manufacturer for some generics. Of 15 product labels we checked, 10 are clean, 2 are confirmed gluten-free by the maker, and 3 contain an inactive ingredient (typically a source-ambiguous starch) whose botanical origin isn't fully disclosed. None contained confirmed gluten.

Drug context

About Synthroid

Synthroid is a brand name for levothyroxine — the brand-name form of levothyroxine, a synthetic thyroid hormone for hypothyroidism. The active ingredient is the same across brand and generic versions, but inactive ingredients (excipients) can differ between manufacturers, which is the whole point of this page.

Why this matters

Different manufacturers, different ingredients

Generics of Synthroid use the same active ingredient, but they aren't required to use the same inactive ingredients. Your pharmacy may switch which manufacturer they dispense between fills, sometimes without telling you. The list below shows each manufacturer's product label as a separate entry, because that's the granularity that actually matters when you're celiac.

The labels

The 15 we checked

01

Mylan manufacturer-attested gluten-free

Plogsted list · Levothyroxine all strengths [Mylan] · label dated 2019-04-23

Manufacturer confirmed gluten-free (Plogsted 2019-04-23)
View source label →
02

UDL/Mylan manufacturer-attested gluten-free

Plogsted list · Levothyroxine all strengths [UDL/Mylan] · label dated 2019-04-23

Manufacturer confirmed gluten-free (Plogsted 2019-04-23)
View source label →
03

Lannett worth a call to confirm

Plogsted list · Levothyroxine all strengths [Lannett] · label dated 2019-04-23
View source label →
04

Neopharma worth a call to confirm

Plogsted list · Levothyroxine all strengths [Neopharma] · label dated 2019-04-23
View source label →
05

Sandoz worth a call to confirm

Plogsted list · Levothyroxine all strengths [Sandoz] · label dated 2019-04-23
View source label →
06

Coupler LLC nothing flagged on the label

US label (DailyMed) · LEVOTHYROXINE SODIUM TABLET [COUPLER LLC] · label dated Jun 17, 2026

Inactive ingredients CROSCARMELLOSE SODIUM · FD&C RED NO. 40 · MAGNESIUM STEARATE · MANNITOL · SODIUM BICARBONATE · STARCH, CORN
View source label →
07

Fosun Pharma USA Inc. nothing flagged on the label

US label (DailyMed) · LEVOTHYROXINE SODIUM (LEVOTHYROXINE SODIUM ANHYDROUS) INJECTION, POWDER, LYOPHILIZED, F… · label dated Jun 15, 2026

Inactive ingredients MANNITOL · SODIUM HYDROXIDE · SODIUM PHOSPHATE, DIBASIC, HEPTAHYDRATE
View source label →
08

Coupler LLC nothing flagged on the label

US label (DailyMed) · LEVOTHYROXINE SODIUM TABLET [COUPLER LLC] · label dated Jun 11, 2026

Inactive ingredients CROSCARMELLOSE SODIUM · FD&C BLUE NO. 1 · FD&C BLUE NO. 2 · FD&C RED NO. 40 · FD&C YELLOW NO. 6 · MAGNESIUM STEARATE · MANNITOL · SODIUM BICARBONATE · STARCH, CORN
View source label →
09

Coupler LLC nothing flagged on the label

US label (DailyMed) · LEVOTHYROXINE SODIUM TABLET [COUPLER LLC] · label dated Jun 08, 2026

Inactive ingredients CELLULOSE, MICROCRYSTALLINE · CROSCARMELLOSE SODIUM · D&C YELLOW NO. 10 · FD&C YELLOW NO. 6 · SILICON DIOXIDE · SODIUM STEARYL FUMARATE
View source label →
10

NCS HealthCare of KY, LLC dba Vangard Labs nothing flagged on the label

US label (DailyMed) · LEVOTHYROXINE SODIUM TABLET [NCS HEALTHCARE OF KY, LLC DBA VANGARD LABS] · label dated Jun 08, 2026

Inactive ingredients ACACIA · ALUMINUM OXIDE · CELLULOSE, MICROCRYSTALLINE · D&C RED NO. 27 · D&C YELLOW NO. 10 · FD&C BLUE NO. 1 · FD&C BLUE NO. 2 · FD&C RED NO. 40 · FD&C YELLOW NO. 6 · LACTOSE, UNSPECIFIED FORM · MAGNESIUM STEARATE · SILICON DIOXIDE · SODIUM STARCH GLYCOLATE TYPE A POTATO · STARCH, CORN
View source label →
11

Northwestern Memorial HealthCare nothing flagged on the label

US label (DailyMed) · LEVOTHYROXINE TABLET [NORTHWESTERN MEMORIAL HEALTHCARE] · label dated Jun 05, 2026
View source label →
12

Coupler LLC nothing flagged on the label

US label (DailyMed) · LEVOTHYROXINE SODIUM TABLET [COUPLER LLC] · label dated Jun 03, 2026

Inactive ingredients CROSCARMELLOSE SODIUM · D&C RED NO. 27 · FD&C BLUE NO. 1 · MAGNESIUM STEARATE · MANNITOL · SODIUM BICARBONATE · STARCH, CORN
View source label →
13

Coupler LLC nothing flagged on the label

US label (DailyMed) · LEVOTHYROXINE SODIUM TABLET [COUPLER LLC] · label dated May 28, 2026

Inactive ingredients CROSCARMELLOSE SODIUM · D&C YELLOW NO. 10 · FD&C YELLOW NO. 6 · MAGNESIUM STEARATE · MANNITOL · SODIUM BICARBONATE · STARCH, CORN
View source label →
14

Coupler LLC nothing flagged on the label

US label (DailyMed) · LEVOTHYROXINE SODIUM TABLET [COUPLER LLC] · label dated May 28, 2026

Inactive ingredients CROSCARMELLOSE SODIUM · FD&C BLUE NO. 2 · MAGNESIUM STEARATE · MANNITOL · SODIUM BICARBONATE · STARCH, CORN
View source label →
15

Bryant Ranch Prepack nothing flagged on the label

US label (DailyMed) · LEVOTHYROXINE SODIUM TABLET [BRYANT RANCH PREPACK] · label dated Jun 25, 2026

Inactive ingredients FD&C BLUE NO. 1 ALUMINUM LAKE · FD&C RED NO. 40 · FD&C YELLOW NO. 6 · MAGNESIUM STEARATE · MICROCRYSTALLINE CELLULOSE · SILICON DIOXIDE · SODIUM STARCH GLYCOLATE TYPE A POTATO
View source label →

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Background

What “gluten in a medication” actually means

Gluten enters drugs through their excipients — the inactive ingredients used to bind, coat, fill, or stabilize the dose. The main concern is wheat starch as a filler. Source-ambiguous starches (plain “starch”, pregelatinized starch, sodium starch glycolate, modified starch) get flagged for verification because their botanical origin isn't always disclosed on the label.

The 2024 Mangione et al. pediatric NDC analysis (689 NDCs across the top 100 pediatric medications) found 1.5% contained gluten outright; another 25.7% couldn't be confirmed either way. Liquid and oral-suspension formulations carry disproportionate risk because wheat starch is a common thickener. Full methodology →

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