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Novothyrox Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 4/12/2016

Novothyrox (levothyroxine sodium) is a manmade form of a hormone produced by the thyroid gland used as replacement or supplemental therapy in congenital or acquired hypothyroidism. Novothyrox is also used to treat or prevent various types of euthyroid goiters, including thyroid nodules, subacute or chronic lymphocytic thyroiditis (Hashimoto's thyroiditis), multinodular goiter and, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer. The brand name Novothyrox is discontinued, but generic versions may be available. Side effects are of Novothyrox (levothyroxine sodium) uncommon and generally due to a therapeutic overdose. Side effects of Novothyrox (levothyroxine sodium) can include:

  • fatigue
  • sweating
  • fever
  • headache
  • anxiety
  • weakness
  • heart problems
  • diarrhea
  • vomiting
  • flushing, and
  • menstrual irregularities

The average full replacement dose of Novothyrox is approximately 1.7 mcg/kg/day (e.g., 100-125 mcg/day for a 70 kg adult). Novothyrox may interact with dopamine, glucocorticoids, octreotide, lithium, amiodarone, iodide, antacids, orlistat, steroids, nicotinic acid, salicylates, nonsteroidal anti-inflammatory drugs (NSAIDs), phenytoin, carbamazepine, beta-adrenergic antagonists, anticoagulants, antidepressants, antidiabetic or insulin therapy, digitalis, growth hormones, ketamine, bronchodilators, and sympathomimetics. Tell your doctor all medications and supplements you use. The possibility of fetal harm while taking Novothyrox appears remote. Novothyrox should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated. Although thyroid hormones are excreted only minimally in breast milk, nursing women should exercise caution when taking this drug. However, adequate replacement doses of levothyroxine are generally needed to maintain normal lactation. Consult your doctor before breastfeeding.

Our Novothyrox (levothyroxine sodium) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Novothyrox FDA Prescribing Information: Side Effects
(Adverse Reactions)


Adverse reactions associated with levothyroxine therapy are primarily those of hyperthyroidism due to therapeutic overdosage (see PRECAUTIONS and OVERDOSAGE). They include the following:

General: fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating;

Central nervous system: headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia;

Musculoskeletal: tremors, muscle weakness;

Cardiovascular: palpitations, tachycardia, arrythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest;

Respiratory: dyspnea;

Gastrointestinal: diarrhea, vomiting, abdominal cramps and elevations in liver function tests;

Dermatologic: hair loss, flushing;

Endocrine: decreased bone mineral density;

Reproductive: menstrual irregularities, impaired fertility.

Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in children receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants and premature closure of the epiphyses in children with resultant compromised adult height.

Seizures have been reported rarely with the institution of levothyroxine therapy.

Inadequate levothyroxine dosage will produce or fail to ameliorate the signs and symptoms of hypothyroidism.

Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various GI symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness and wheezing. Hypersensitivity to levothyroxine itself is not known to occur.

Read the entire FDA prescribing information for Novothyrox (Levothyroxine Sodium Tablets)

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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