Prescription medicine
Levothyroxine Brand names: Tirosint, Synthroid, Unithroid, Levoxyl, Thyquidity
Levothyroxine (Synthroid) is a prescription medicine with an FDA approval on record since 2000. FDA's NDC Directory lists it from 36 generic labelers, and pharmacies paid $0.0588 per levothyroxine 112 mcg tablet in the October 7, 2026 NADAC survey.
- Generic listed
- Boxed warning
Check it at the source: the levothyroxine FDA label on DailyMed (effective February 20, 2024, AbbVie Inc.); the NDA 21210 record on Drugs@FDA; every levothyroxine label on DailyMed.
Highlights of the record
FDA label of February 20, 2024; NDC Directory, Drugs@FDA and Orange Book, October 8, 2026; NADAC October 7, 2026
NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS.
Thyroid hormones, including SYNTHROID, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life - threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects [see Adverse Reactions ( 6 ), Drug Interactions ( 7.7 ), and Overdosage ( 10 )]. WARNING: NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS See full prescribing information for complete boxed warning. Thyroid hormones, including SYNTHROID , should not be used for the treatment of obesity or for weight loss. Doses beyond the range of daily hormonal requirements may produce serious or even life - threatening manifestations of toxicity ( 6 , 10 ).
Used for
From the label: indications and usageHypothyroidism SYNTHROID is indicated in adult and pediatric patients, including neonates, as a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism.
Forms and strengths
- 5ml
- 0.025 mg
- 0.05 mg
- 0.075 mg
- 0.088 mg
- 0.1 mg
- 0.112 mg
- 0.125 mg
- 0.137 mg
- 0.15 mg
- 0.175 mg
Tablet; capsule; injection (powder) (lyophilized) for solution; solution; injection (solution).
On the market
- Earliest approval on file
- August 21, 2000 Unithroid, Stevens J; Drugs@FDA’s file, where older or withdrawn approvals can be missing
- Generic approvals
- 20 first June 5, 2002; 11 with a marketed status in Drugs@FDA
- Labelers listed (NDC)
- 51 of which 36 under generic applications, 19 under brand applications, repackagers included
- Last listed patent
- September 26, 2044 Tirosint-Sol oral solution; not a generic launch date
Supply and safety
- Pharmacy cost (NADAC)
- $0.0588 per tablet Levothyroxine 112 mcg tablet
- Shortage (FDA)
- No current entry
- Recalls by its makers (FDA)
- 128 since 2012 0 Class I among all firms' recalls; latest August 6, 2026; 2 more by firms not listed as its makers
- FAERS reports
- 300,456 through July 30, 2026
What is levothyroxine used for?
From the label: indications and usageHypothyroidism SYNTHROID is indicated in adult and pediatric patients, including neonates, as a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism. Pituitary Thyrotropin (Thyroid -Stimulating Hormone, TSH) Suppression SYNTHROID is indicated in adult and pediatric patients, including neonates, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer. […]
Conditions named in the indications of levothyroxine's FDA labels, with every medicine labeled for each:
FDA pharmacologic class: l-Thyroxine.
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 patient leaflet for levothyroxine say first?
The FDA-approved Medication Guide or Patient Information that comes with the medicine, in its own words.
From the patient leaflet: What is the most important information I should know about LEVOXYL?Do not use LEVOXYL to treat weight problems or weight loss. Do not take more LEVOXYL than your healthcare provider prescribes for you to take. Over dosage or taking too much LEVOXYL may cause life-threatening side effects or death.
Source: FDA drug label (LEVOXYL), Pfizer Laboratories Div Pfizer Inc, effective December 15, 2020 (SPL set 758588c3-c63e-491b-0aa2-4f50d80cb174), via openFDA; the full label on DailyMed
Is there a generic for levothyroxine (Synthroid)?
The FDA approved the first generic levothyroxine on June 5, 2002. 20 generic applications are approved; 11 of them carry a current (not discontinued) marketing status in Drugs@FDA; that status is not evidence that the generic is on sale.
FDA's NDC Directory lists levothyroxine from 36 labelers under a generic (ANDA) application and from 19 brand labelers. A listing means the company has registered the product for sale; it does not show that every pharmacy stocks it.
The Orange Book lists no patent for Synthroid tablets; a patent listed only for Tirosint-Sol oral solution runs to September 26, 2044. A patent or exclusivity date is not the date a generic goes on sale: court cases and settlements move it either way.
- 2000 earliest approval on file
- 2002 first generic approved
- 2044 last listed patent
- red ticks recalls
Source: Drugs@FDA, FDA NDC Directory and the Orange Book (openFDA bulk files, October 8, 2026)
What do pharmacies pay for levothyroxine (Synthroid)?
In CMS's NADAC survey of October 7, 2026, pharmacies paid $0.0588 per Levothyroxine 112 mcg tablet, down 12% from $0.0665 on October 8, 2025. Prices per unit in the table differ many-fold by strength, form and brand, so compare like with like. The chart's scale runs from the lowest to the highest price shown, not from zero. NADAC is what retail pharmacies paid their wholesalers, per unit, in CMS's monthly survey; what a patient pays depends on insurance and the pharmacy.
- Levothyroxine 112 mcg tablet (generic)
- Synthroid 200 mcg tablet (brand)
| Strength and form | Brand or generic | Pharmacy cost | 30 tablets, or one pen or vial | 12-month change |
|---|---|---|---|---|
| Levothyroxine 100 mcg tablet | Generic | $0.0497 per tablet | $1.49 | -10% |
| Levothyroxine 112 mcg tablet | Generic | $0.0588 per tablet | $1.76 | -12% |
| Levothyroxine 125 mcg tablet | Generic | $0.057 per tablet | $1.71 | -13% |
| Levothyroxine 137 mcg tablet | Generic | $0.0639 per tablet | $1.92 | -12% |
| Levothyroxine 150 mcg tablet | Generic | $0.0586 per tablet | $1.76 | -17% |
| Levothyroxine 175 mcg tablet | Generic | $0.0735 per tablet | $2.20 | -18% |
| Levothyroxine 200 mcg tablet | Generic | $0.081 per tablet | $2.43 | -6% |
| Levothyroxine 25 mcg tablet | Generic | $0.0351 per tablet | $1.05 | -15% |
| Levothyroxine 300 mcg tablet | Generic | $0.104 per tablet | $3.13 | -10% |
| Levothyroxine 50 mcg tablet | Generic | $0.0407 per tablet | $1.22 | -21% |
| Levothyroxine 75 mcg tablet | Generic | $0.0461 per tablet | $1.38 | -15% |
| Levothyroxine 88 mcg tablet | Generic | $0.0495 per tablet | $1.48 | -15% |
| Levoxyl 100 mcg tablet | Brand | $0.970 per tablet many times the lowest per-tablet cost; NADAC records the price, not why | $29.09 | +5% |
| Levoxyl 112 mcg tablet | Brand | $1.12 per tablet many times the lowest per-tablet cost; NADAC records the price, not why | $33.48 | +5% |
Source: CMS National Average Drug Acquisition Cost (NADAC) survey, October 7, 2026: what retail pharmacies paid per unit; not a counter price
Has levothyroxine been recalled?
The FDA's Enforcement Report lists 130 recalls naming levothyroxine since 2012: 0 Class I (the most serious), 128 Class II, 2 Class III; 61 still ongoing. 2 of them are by firms that FDA's NDC Directory does not list as a maker of levothyroxine and that hold no application for it in Drugs@FDA, such as compounding pharmacies or bulk-ingredient suppliers; the recall notice names the product recalled. A recall names products and lots, not every product of the medicine.
| Started | Class | Company | Reason |
|---|---|---|---|
| August 6, 2026 | Class II | ACCORD HEALTHCARE, INC. | Subpotent Drug |
| July 13, 2026 | Class II | Major Pharmaceuticals | Subpotent Drug |
| June 8, 2026 | Class II | ACCORD HEALTHCARE, INC. | Subpotent Drug |
| February 26, 2026 | Class II | MACLEODS PHARMA USA, INC | Subpotent Drug |
| December 31, 2025 | Class II | Alvogen, Inc | Product Mix-Up: A single bottle of this lot was reported by a pharmacy to contain 88 mcg tablets instead of 150 mcg tablets. |
| September 16, 2025 | Class II | ACCORD HEALTHCARE, INC. | Subpotent: During long term stability testing of Levothyroxine Sodium Tablets USP for 88 mcg, the assay content was observed below the approved specification … |
| July 29, 2025 | Class II | Pfizer | Subpotent drug |
| June 20, 2025 | Class II | ACCORD HEALTHCARE, INC. | Subpotent Drug: Assay below the approved specification |
Source: FDA Enforcement Report (drug recalls) via openFDA, through October 8, 2026
What does the levothyroxine label say about other medicines?
The levothyroxine label names 38 other medicines in its interaction, contraindication or warning sections. The labels of 24 other medicines name levothyroxine. The sentences are the labels' own; a label lists what its studies and reports found, not every interaction.
| Medicine named | Section | What the label says |
|---|---|---|
| Amiodarone | drug interactions | Other drugs: Amiodarone; Amiodarone inhibits peripheral conversion of levothyroxine (T4) to triiodothyronine (T3) and may cause isolated biochemical changes (increase in serum free-T4, and decreased or normal free-T3) in clinically euthyroid patients. |
| Amitriptyline | drug interactions | Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and SYNTHROID may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. |
| Asparaginase | drug interactions | Androgens / Anabolic Steroids Asparaginase Glucocorticoids Slow-Release Nicotinic Acid These drugs may decrease serum TBG concentration. |
| Biotin | drug interactions | Biotin Biotin supplementation is known to interfere with thyroid hormone immunoassays that are based on a biotin and streptavidin interaction, which may result in erroneous thyroid hormone test results. |
| Calcium carbonate | drug interactions | Drug or Drug Class Effect Phosphate Binders (e.g., calcium carbonate, ferrous sulfate, sevelamer, lanthanum) Phosphate binders may bind to levothyroxine. |
| Carbamazepine | drug interactions | Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. |
| Cholestyramine | drug interactions | Bile 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. |
| Colesevelam | drug interactions | Bile 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. |
| Colestipol | drug interactions | Bile 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. |
| Dexamethasone | drug interactions | Glucocorticoids (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. |
| Diazepam | drug interactions | Drug or Drug Class: Chloral Hydrate Diazepam Ethionamide Lovastatin Metoclopramide 6-Mercaptopurine Nitroprusside Para-aminosalicylate sodium Perphenazine Resorcinol (excessive topical use) Thiazide Diuretics; … |
| Ferrous sulfate | drug interactions | Drug or Drug Class Effect Phosphate Binders (e.g., calcium carbonate, ferrous sulfate, sevelamer, lanthanum) Phosphate binders may bind to levothyroxine. |
| Furosemide | drug interactions | Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. |
| Heparin | drug interactions | Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. |
Every other medicine the levothyroxine label names
| Medicine named | Section | What the label says |
|---|---|---|
| Hydrocortisone | drug interactions | Glucocorticoids (hydrocortisone ≥ 100 mg/day or equivalent); |
| Imatinib | drug interactions | Concurrent use of tyrosine-kinase inhibitors such as imatinib may cause hypothyroidism. |
| Ketamine | drug interactions | Concurrent use of ketamine and SYNTHROID may produce marked hypertension and tachycardia. |
| Lanthanum | drug interactions | Drug or Drug Class Effect Phosphate Binders (e.g., calcium carbonate, ferrous sulfate, sevelamer, lanthanum) Phosphate binders may bind to levothyroxine. |
| Lithium | drug interactions | Drug or Drug Class: Aminoglutethimide Amiodarone Iodide (including iodine-containing Radiographic contrast agents) Lithium Methimazole Propylthioracil (PTU) Sulfonamides Tolbutamide; … |
| Lovastatin | drug interactions | Drug or Drug Class: Chloral Hydrate Diazepam Ethionamide Lovastatin Metoclopramide 6-Mercaptopurine Nitroprusside Para-aminosalicylate sodium Perphenazine Resorcinol (excessive topical use) Thiazide … |
| Methadone | drug interactions | Drug or Drug Class: Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin / Methadone 5-Fluorouracil Mitotane Tamoxifen; … |
| Methimazole | drug interactions | Drug or Drug Class: Aminoglutethimide Amiodarone Iodide (including iodine-containing Radiographic contrast agents) Lithium Methimazole Propylthioracil (PTU) Sulfonamides Tolbutamide; … |
| Metoclopramide | drug interactions | Drug or Drug Class: Chloral Hydrate Diazepam Ethionamide Lovastatin Metoclopramide 6-Mercaptopurine Nitroprusside Para-aminosalicylate sodium Perphenazine Resorcinol (excessive topical use) Thiazide … |
| Mitotane | drug interactions | Drug or Drug Class: Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin / Methadone 5-Fluorouracil Mitotane Tamoxifen; … |
| Octreotide | drug interactions | Drug or Drug Class: Dopamine/Dopamine Agonists Glucocorticoids Octreotide; Effect: Use of these agents may result in a transient reduction in TSH secretion when administered at the following doses … |
| Orlistat | drug interactions | Orlistat Monitor patients treated concomitantly with orlistat and SYNTHROID for changes in thyroid function. |
| Perphenazine | drug interactions | Drug or Drug Class: Chloral Hydrate Diazepam Ethionamide Lovastatin Metoclopramide 6-Mercaptopurine Nitroprusside Para-aminosalicylate sodium Perphenazine Resorcinol (excessive topical use) Thiazide … |
| Phenobarbital | drug interactions | Drug or Drug Class Effect Phenobarbital Rifampin Phenobarbital has been shown to reduce the response to thyroxine. |
| Phenytoin | drug interactions | … albumin, so that a single high dose can acutely lower the total T4 level. Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total and free T4 may be reduced by 20% to … |
| Propranolol | drug interactions | Beta-adrenergic antagonists (e.g., Propranolol > 160 mg/day); In patients treated with large doses of propranolol (> 160 mg/day), T3 and T4 levels change, TSH levels remain normal, and patients are … |
| Propylthiouracil | drug interactions | Drug or Drug Class: Amiodarone Beta-adrenergic antagonists - (e.g., Propranolol > 160 mg/day) Glucocorticoids -(e.g., Dexamethasone ≥ 4 mg/day) Propylthiouracil (PTU); … |
| Rifampin | drug interactions | Drug or Drug Class Effect Phenobarbital Rifampin Phenobarbital has been shown to reduce the response to thyroxine. |
| Sertraline | drug interactions | Administration of sertraline in patients stabilized on SYNTHROID may result in increased SYNTHROID requirements. |
| Sevelamer | drug interactions | Drug or Drug Class Effect Phosphate Binders (e.g., calcium carbonate, ferrous sulfate, sevelamer, lanthanum) Phosphate binders may bind to levothyroxine. |
| Somatropin | drug interactions | Growth Hormones - Somatrem - Somatropin Excessive use of thyroid hormones with growth hormones may accelerate epiphyseal closure. |
| Sucralfate | drug interactions | Proton Pump Inhibitors Sucralfate Antacids (e.g., aluminum & magnesium hydroxides, simethicone) Gastric acidity is an essential requirement for adequate absorption of levothyroxine. |
| Tamoxifen | drug interactions | Drug or Drug Class: Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin / Methadone 5-Fluorouracil Mitotane Tamoxifen; … |
| Theophylline | drug interactions | Methylxanthine Bronchodilators - (e.g., Theophylline) Decreased theophylline clearance may occur in hypothyroid patients; clearance returns to normal when the euthyroid state is achieved. |
Other labels that name levothyroxine
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 do FAERS reports show for levothyroxine?
The FDA Adverse Event Reporting System holds 300,456 reports that list levothyroxine among the medicines taken, through July 30, 2026, each a report of something that happened, not proof the medicine caused it; 19,275 are coded as a death and 85,074 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is.
Reports received each year
The most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026
What else is labeled for the same conditions as levothyroxine?
1 other medicine is given the same way (oral) and in the same FDA class as levothyroxine or labeled mainly for the same use (hypothyroidism), the same class first. Hypothyroidism lists all 2 medicines labeled for it, by any route. They are listed as records, not as substitutes: whether one can replace another is a prescriber's decision.
| Medicine | Shared indication | Generic labelers (oral) | Pharmacy cost | Shortage |
|---|---|---|---|---|
| Liothyronine | Hypothyroidism | 16 labelers | $0.294 per tablet 25 mcg tablet | No current entry |
Source: FDA drug labels (indications), NDC Directory, NADAC of October 7, 2026, FDA shortages (October 8, 2026)
How does levothyroxine compare with medicines for the same use?
1 side-by-side page set levothyroxine beside a medicine whose label shares a use: approvals, generics, pharmacy cost, warnings and supply.
What next?
- Levothyroxine side effects
- the label's list beside FAERS reports
- Check an interaction
- what two or more labels say about each other