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Levothyroxine Sodium

500 ug/5mL · Injection, Powder, Lyophilized, for Solution

  • Prescription only
  • l-Thyroxine
Active substance
Levothyroxine Sodium
Made by
Zydus Pharmaceuticals USA Inc.

Quoted from the official source. Not yet reviewed by Mediclarum — the leaflet in your pack is authoritative.

At a glance

Quoted from the official label · 2025-09-16

What it is

l-Thyroxine

Used for
  • Levothyroxine sodium for injection is indicated for the treatment of myxedema coma.
The label’s usual adult dose

( 2.1 ) Reconstitute the lyophilized levothyroxine sodium for injection by aseptically adding 5 mL of 0.9% sodium chloride injection, USP.

Full directions ↓
Serious warning

NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS Thyroid hormones, including levothyroxine sodium for injection, should not be used for the treatment of obesity or for weight loss.

All warnings ↓
Good to know
  • Prescription only
  • FDA enforcement reports list no ongoing recall, and none from the last two years, for this product code · checked 2026-10-02
438other products contain Levothyroxine Sodium — compare makers, forms and strengths

Every line above is selected, not written, from the official label. Nothing is reworded. DailyMed

What it is for

Important Limitations of Use:

  • Levothyroxine sodium for injection is indicated for the treatment of myxedema coma.
  • The relative bioavailability between levothyroxine sodium for injection and oral levothyroxine products has not been established.
  • Caution should be used when switching patients from oral levothyroxine products to levothyroxine sodium for injection as accurate dosing conversion has not been studied.
  • Levothyroxine sodium is an L-thyroxine product.
  • Levothyroxine (T 4 ) sodium for injection is indicated for the treatment of myxedema coma.
  • ( 1 ) Important Limitations of Use:
  • The relative bioavailability of this drug has not been established.
  • Use caution when converting patients from oral to intravenous levothyroxine.
  • ( 1 )

From the official label · 2025-09-16 · DailyMed

How it works

From this product’s own US prescribing label.

Thyroid hormones exert their physiologic actions through control of DNA transcription and protein synthesis.

Triiodothyronine (T 3 ) and levothyroxine (T 4 ) diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA.

How the body breaks it down

Thyroid hormones are also metabolized via conjugation with glucuronides and sulfates and excreted directly into the bile and gut where they undergo enterohepatic recirculation.

Quoted from the prescribing label, sections “Mechanism of Action” and “Pharmacokinetics”. DailyMed · 2025-09-16

Serious warning

The strongest warning the FDA requires. It is printed in a box at the top of the label.

  • NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS Thyroid hormones, including levothyroxine sodium for injection, should not be used for the treatment of obesity or for weight loss.
  • ( 5.3 ) Larger doses may produce serious or even life threatening manifestations of toxicity.
  • ( 6 ) WARNING:
  • NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS Thyroid hormones, including levothyroxine sodium for injection, should not be used for the treatment of obesity or for weight loss.
  • ( 5.3 ) Larger doses may produce serious or even life threatening manifestations of toxicity.
  • ( 6 )

Quoted from the official label, section “Boxed Warning”.

Do not take it if

None. None. ( 4 )

Quoted from the official label, section “Contraindications”.

How to take it

These directions are for this exact strength and form. Another one is different.

  • An initial intravenous loading dose of levothyroxine sodium for injection between 300 mcg to 500 mcg followed by once daily intravenous maintenance doses between 50 mcg and 100 mcg should be administered, as clinically indicated, until the patient can tolerate oral therapy.
  • ( 2.1 ) Reconstitute the lyophilized levothyroxine sodium for injection by aseptically adding 5 mL of 0.9% sodium chloride injection, USP.
  • Shake vial to ensure complete mixing.
  • Reconstituted drug product is preservative free.
  • Use immediately after reconstitution.
  • Discard any unused portion.
  • ( 2.3 ) Do not add to other IV fluids.
  • ( 2.3 )
  • 2.1 Dosage An initial intravenous loading dose of levothyroxine sodium for injection between 300 mcg to 500 mcg, followed by once daily intravenous maintenance doses between 50 mcg and 100 mcg, should be administered, as clinically indicated, until the patient can tolerate oral therapy.
  • The age, general physical condition, cardiac risk factors and clinical severity of myxedema and duration of myxedema symptoms should be considered when determining the starting and maintenance dosages of levothyroxine sodium for injection.
  • Levothyroxine sodium for injection produces a gradual increase in the circulating concentrations of the hormone with an approximate half-life of 9 days to 10 days in hypothyroid patients.
  • Daily administration of levothyroxine sodium for injection should be maintained until the patient is capable of tolerating an oral dose and is clinically stable.
  • For chronic treatment of hypothyroidism, an oral dosage form of levothyroxine should be used to maintain a euthyroid state.
  • Relative bioavailability between levothyroxine sodium for injection and oral levothyroxine products has not been established.
  • Based on medical practice, the relative bioavailability between oral and intravenous administration of levothyroxine sodium for injection is estimated to be from 48% to 74%.
  • Due to differences in absorption characteristics of patients and the oral levothyroxine product formulations, TSH and thyroid hormone levels should be measured a few weeks after initiating oral levothyroxine and dose adjusted accordingly.
  • 2.2 Dosing in the Elderly and in Patients with Cardiovascular Disease Intravenous levothyroxine may be associated with cardiac toxicity-including arrhythmias, tachycardia, myocardial ischemia and infarction or worsening of congestive heart failure and death—in the elderly and in those with underlying cardiovascular disease.
  • Therefore, cautious use, including doses in the lower end of the recommended range, may be warranted in these populations.
  • 2.3 Reconstitution Directions Reconstitute the lyophilized levothyroxine sodium for injection by aseptically adding 5 mL of 0.9% sodium chloride injection, USP only.
  • Shake vial to ensure complete mixing.
  • The resultant solution will have a final concentration of approximately 20 mcg per mL, 40 mcg per mL and 100 mcg per mL for the 100 mcg, 200 mcg and 500 mcg vials, respectively.
  • Reconstituted drug product is preservative free and is stable for 4 hours.
  • Discard any unused portion.
  • DO NOT ADD LEVOTHYROXINE SODIUM FOR INJECTION TO OTHER IV FLUIDS.
  • Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

Quoted from the official label, section “Dosage & Administration”.

Other warnings

  • Excessive bolus doses of levothyroxine sodium for injection (> 500 mcg) are associated with cardiac complications, particularly in the elderly and in patients with an underlying cardiac condition.
  • Initiate therapy with doses at the lower end of the recommended range.
  • ( 5.1 ) Close observation of the patient following the administration of levothyroxine sodium for injection is advised.
  • ( 5.1 ) Levothyroxine sodium for injection therapy for patients with previously undiagnosed endocrine disorders, including adrenal insufficiency, hypopituitarism and diabetes insipidus, may worsen symptoms of these endocrinopathies.
  • ( 5.2 )
  • 5.1 Risk of Cardiac Complications in Elderly and in Patients with Cardiovascular Disease Excessive bolus dosing of levothyroxine sodium for injection (greater than 500 mcg) are associated with cardiac complications, particularly in the elderly and in patients with an underlying cardiac condition.
  • Adverse events that can potentially be related to the administration of large doses of levothyroxine sodium for injection include arrhythmias, tachycardia, myocardial ischemia and infarction or worsening of congestive heart failure and death.
  • Close observation of the patient following the administration of levothyroxine sodium for injection is advised.
  • 5.2 Need for Concomitant Glucocorticoids and Monitoring for Other Diseases in Patients with Endocrine Disorders Occasionally, chronic autoimmune thyroiditis, which can lead to myxedema coma, may occur in association with other autoimmune disorders such as adrenal insufficiency, pernicious anemia and insulin-dependent diabetes mellitus.
  • Patients should be treated with replacement glucocorticoids prior to initiation of treatment with levothyroxine sodium for injection, until adrenal function has been adequately assessed.
  • Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone.
  • With initiation of levothyroxine sodium for injection, patients with myxedema coma should also be monitored for previously undiagnosed diabetes insipidus.
  • 5.3 Not Indicated for Treatment of Obesity Thyroid hormones, including levothyroxine sodium for injection, 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 ) and Overdosage ( 10 )].

Quoted from the official label, section “Warnings”.

Pregnancy and breastfeeding

  • Pregnancy Category A There are no reported cases of levothyroxine sodium for injection used to treat myxedema coma in patients who were pregnant or lactating.
  • Studies in pregnant women treated with oral levothyroxine to maintain a euthyroid state have not shown an increased risk of fetal abnormalities.
  • Therefore, pregnant patients who develop myxedema should be treated with levothyroxine sodium for injection as the risk of non-treatment is associated with a high probability of significant morbidity or mortality to the maternal patient and the fetus.
  • Adequate replacement doses of thyroid hormones are required to maintain normal lactation.
  • There are no reported cases of levothyroxine sodium for injection used to treat myxedema coma in patients who are lactating.
  • However, such patients should be treated with levothyroxine sodium for injection as the risk of non-treatment is associated with a high probability of significant morbidity or mortality to the nursing patient.
  • IN SPECIFIC POPULATIONS Elderly and those with underlying cardiovascular disease should receive doses at the lower end of the recommended range.
  • ( 8.5 )
  • 8.1 Pregnancy Pregnancy Category A There are no reported cases of levothyroxine sodium for injection used to treat myxedema coma in patients who were pregnant or lactating.
  • Studies in pregnant women treated with oral levothyroxine to maintain a euthyroid state have not shown an increased risk of fetal abnormalities.
  • Therefore, pregnant patients who develop myxedema should be treated with levothyroxine sodium for injection as the risk of non-treatment is associated with a high probability of significant morbidity or mortality to the maternal patient and the fetus.
  • 8.2 Labor and Delivery Patients in labor who develop myxedema have not been reported in the literature.
  • However, patients should be treated with levothyroxine sodium for injection as the risk of non-treatment is associated with a high probability of significant morbidity or mortality to the maternal patient and the fetus.
  • 8.3 Nursing Mothers Adequate replacement doses of thyroid hormones are required to maintain normal lactation.
  • There are no reported cases of levothyroxine sodium for injection used to treat myxedema coma in patients who are lactating.
  • However, such patients should be treated with levothyroxine sodium for injection as the risk of non-treatment is associated with a high probability of significant morbidity or mortality to the nursing patient.
  • 8.4 Pediatric Use Myxedema coma is a disease of the elderly.
  • An approved, oral dosage form of levothyroxine should be used in the pediatric patient population for maintaining a euthyroid state in non-complicated hypothyroidism.
  • 8.5 Geriatric Use and Patients with Underlying Cardiovascular Disease See Section 2, Dosage and Administration, for full prescribing information in the geriatric patient population.
  • Because of the increased prevalence of cardiovascular disease in the elderly, cautious use of levothyroxine sodium for injection in the elderly and in patients with known cardiac risk factors is advised.
  • Atrial fibrillation is a common side effect associated with levothyroxine treatment in the elderly [see Dosage and Administration ( 2 ) and Warnings and Precautions ( 5 )].

Quoted from the official label, section “OTC — Pregnancy or Breast Feeding”.

Other medicines

  • Many drugs affect thyroid hormone pharmacokinetics and metabolism (e.g., synthesis, secretion, catabolism, protein binding and target tissue response) and may alter the therapeutic response to levothyroxine sodium for injection.
  • In addition, thyroid hormones and thyroid status have varied effects on the pharmacokinetics and actions of other drugs (see Section 12.3 ).
  • Many drugs affect thyroid hormone pharmacokinetics and metabolism (e.g., absorption, synthesis, secretion, catabolism, protein binding and target tissue response) and may alter the therapeutic response to levothyroxine sodium for injection.
  • ( 7 , 12.3 )
  • 7.1 Antidiabetic Therapy Addition of levothyroxine to antidiabetic or insulin therapy may result in increased antidiabetic agent or insulin requirements.
  • Careful monitoring of diabetic control is recommended, especially when thyroid therapy is started, changed or discontinued.
  • 7.2 Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy.
  • Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state or when the levothyroxine sodium for injection dose is increased.
  • Prothrombin time should be closely monitored to permit appropriate and timely dosage adjustments.
  • 7.3 Digitalis Glycosides The therapeutic effects of digitalis glycosides may be reduced by levothyroxine.
  • Serum digitalis glycoside levels may be decreased when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides.
  • 7.4 Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines.
  • Toxic effects may include increased risk of cardiac arrhythmias and CNS stimulation; onset of action of tricyclics may be accelerated.
  • Administration of sertraline in patients stabilized on levothyroxine may result in increased levothyroxine requirements.
  • 7.5 Ketamine Concurrent use may produce marked hypertension and tachycardia; cautious administration to patients receiving thyroid hormone therapy is recommended.
  • 7.6 Sympathomimetics Concurrent use may increase the effects of sympathomimetics or thyroid hormone.
  • Thyroid hormones may increase the risk of coronary insufficiency when sympathomimetic agents are administered to patients with coronary artery disease.
  • 7.7 Drug-Laboratory Test Interactions Changes in thyroxine binding globulin (TBG) concentration must be considered when interpreting levothyroxine and triiodothyronine values, which necessitates measurement and evaluation of unbound (free) hormone and/or determination of the free levothyroxine index.
  • Pregnancy, infectious hepatitis, estrogens, estrogen containing oral contraceptives and acute intermittent porphyria increase TBG concentrations.
  • Decreases in TBG concentrations are observed in nephrosis, severe hypoproteinemia, severe liver disease, acromegaly and after androgen or corticosteroid therapy.
  • Familial hyper or hypo thyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9,000.

Quoted from the official label, section “Drug Interactions”.

If you take too much

In an emergency, call your local emergency number or a poison control centre.

  • In general, the signs and symptoms of overdosage with levothyroxine are those of hyperthyroidism [see Warnings and Precautions ( 5 ) and Adverse Reactions ( 6 )].
  • In addition, confusion and disorientation may occur.
  • Cerebral embolism, shock, coma and death have been reported.
  • Excessive doses of levothyroxine sodium for injection (greater than 500 mcg) are associated with cardiac complications in patients with underlying cardiac disease.
  • Treatment of Overdosage Levothyroxine sodium for injection should be reduced in dose or temporarily discontinued if signs or symptoms of overdosage occur.
  • To obtain up-to-date information about the treatment of overdose, a good resource is the certified Regional Poison Control Center.
  • In managing overdosage, consider the possibility of multiple drug overdoses, interaction among drugs and unusual drug kinetics in the patient.
  • In the event of an overdose, appropriate supportive treatment should be initiated as dictated by the patient's medical status.

Quoted from the official label, section “Overdosage”.

Use in children

Myxedema coma is a disease of the elderly. An approved, oral dosage form of levothyroxine should be used in the pediatric patient population for maintaining a euthyroid state in non-complicated hypothyroidism.

Quoted from the official label, section “Pediatric Use”.

Side effects

  • Excessive doses of levothyroxine can predispose to signs and symptoms compatible with hyperthyroidism.
  • The signs and symptoms of thyrotoxicosis include, but are not limited to:
  • exophthalmic goiter, weight loss, increased appetite, palpitations, nervousness, diarrhea, abdominal cramps, sweating, tachycardia, increased pulse and blood pressure, cardiac arrhythmias, angina pectoris, tremors, insomnia, heat intolerance, fever and menstrual irregularities.
  • Excessive doses of L-thyroxine can predispose to signs and symptoms compatible with hyperthyroidism.
  • ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Zydus Pharmaceuticals (USA) Inc. at 1-877-993-8779 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Quoted from the official label, section “Adverse Reactions”.

Strengths and forms

  • FORMS AND STRENGTHS Levothyroxine sodium for injection is a white to off-white color lyophilized powder filled in amber colored glass vial and are supplied as:
  • 100 mcg single-dose vial 200 mcg single-dose vial 500 mcg single-dose vial Lyophilized powder for injection in single dose vials:
  • 100 mcg, 200 mcg and 500 mcg.
  • ( 3 )

Quoted from the official label, section “Dosage Forms & Strengths”.

What it looks like and how it is packed

  • 16.1 How Supplied Levothyroxine sodium for injection is a white to off-white color lyophilized powder filled in amber colored glass vial and are supplied as follows:
  • Strength (mg of levothyroxine sodium) Reconstituted Concentration Pack NDC 100 mcg/vial 20 mcg/mL 100 mcg Single-dose vial 70710-1833-1 Carton of one (1) Single-dose vial 70710-1833-1 200 mcg/vial 40 mcg/mL 200 mcg Single-dose vial 70710-1834-1 Carton of one (1) Single-dose vial 70710-1834-1 500 mcg/vial 100 mcg/mL 500 mcg Single-dose vial 70710-1835-1 Carton of one (1) Single-dose vial 70710-1835-1
  • 16.2 Storage and Handling Protect from light and store dry product at 20°C to 25°C (68°F to 77°F) [see USP Controlled Room Temperature].
  • Reconstituted drug product is preservative free.
  • Discard any unused portion.
  • This container closure is not made with natural rubber latex.
  • Call your doctor for medical advice about side effects.
  • You may report side effects to FDA at 1-800-FDA-1088.
  • Please address medical inquiries to, MedicalAffairs@zydususa.com or Tel.: 1-877-993-8779.
  • Levothyroxine sodium for injection is a white to off-white color lyophilized powder filled in amber colored glass vial and are supplied as follows:
  • Strength (mg of levothyroxine sodium) Reconstituted Concentration Pack NDC 100 mcg/vial 20 mcg/mL 100 mcg Single-dose vial 70710-1833-1 Carton of one (1) Single-dose vial 70710-1833-1 200 mcg/vial 40 mcg/mL 200 mcg Single-dose vial 70710-1834-1 Carton of one (1) Single-dose vial 70710-1834-1 500 mcg/vial 100 mcg/mL 500 mcg Single-dose vial 70710-1835-1 Carton of one (1) Single-dose vial 70710-1835-1

Quoted from the official label, section “How Supplied”.

How to store it

  • Protect from light and store dry product at 20°C to 25°C (68°F to 77°F) [see USP Controlled Room Temperature].
  • Reconstituted drug product is preservative free.
  • Discard any unused portion.
  • This container closure is not made with natural rubber latex.
  • Call your doctor for medical advice about side effects.
  • You may report side effects to FDA at 1-800-FDA-1088.
  • Please address medical inquiries to, MedicalAffairs@zydususa.com or Tel.: 1-877-993-8779.

Quoted from the official label, section “Storage and Handling”.

What is in it

  • Levothyroxine Sodium for Injection contains synthetic crystalline levothyroxine (L-thyroxine) sodium salt.
  • Levothyroxine sodium, USP has a molecular formula of C 15 H 10 I 4 NNaO 4 , a molecular weight of 798.85 g/mol (anhydrous), and the following structural formula:
  • Levothyroxine Sodium for Injection is a sterile, preservative-free lyophilized powder consisting of the active ingredient, levothyroxine sodium, USP and the excipients mannitol and sodium hydroxide for pH adjustment in single-dose amber glass vials.
  • Levothyroxine Sodium for Injection is available at three dosage strengths:
  • 100 mcg per vial, 200 mcg per vial and 500 mcg per vial.
  • Image

Quoted from the official label, section “Description”.

Ingredients people check for

Lactose, gluten, dyes, sugars and other ingredients that matter with an allergy, intolerance or diet — as this product’s FDA label lists them.

The stored label for this product has no list of inactive ingredients. The list on the pack is the one to check.

Quoted from the FDA label. A label that does not name an ingredient is not a guarantee that the product is free of it, and formulations change. With an allergy, check the pack and ask a pharmacist.

Every version of this medicine (7)

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Same active substance, strength and form in other countries

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Every strength and form (42)

Details

Made byZydus Pharmaceuticals USA Inc.
Active substanceLevothyroxine Sodium
Used inHormones, such as thyroid and steroids
Strength500 ug/5mL
FormInjection, Powder, Lyophilized, for Solution
RouteIntravenous
Packs1 VIAL, SINGLE-DOSE in 1 CARTON / 5 mL in 1 VIAL, SINGLE-DOSE
NDC70710-1835

Source: NDC Directory · 2026-09-13 · not reviewed by a clinician

Source: US Food and Drug Administration, NDC Directory. Reuse terms: US government work (FDA).

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Other strengths and forms

384 products are sold under this name. Grouped by form; a number on a strength means several companies make it.

Show all forms · 5 forms

Same active substance

These contain the same substance. That does not mean one can replace another — ask a pharmacist.

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