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Cytomel Side Effects

Generic Name: liothyronine

Note: This document contains side effect information about liothyronine. Some of the dosage forms listed on this page may not apply to the brand name Cytomel.

For the Consumer

Applies to liothyronine: oral tablet

Other dosage forms:

Along with its needed effects, liothyronine (the active ingredient contained in Cytomel) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Get emergency help immediately if any of the following symptoms of overdose occur while taking liothyronine:

  • Arm, back or jaw pain
  • changes in appetite
  • changes in menstrual periods
  • chest pain or discomfort
  • chest tightness or heaviness
  • cold clammy skin
  • confusion
  • decreased urine output
  • diarrhea
  • dilated neck veins
  • dizziness
  • extreme fatigue
  • fainting
  • fast, slow, pounding, or irregular heartbeat or pulse
  • fever
  • hand tremors
  • headache
  • increased bowel movements
  • irregular breathing
  • irritability
  • leg cramps
  • lightheadedness
  • menstrual changes
  • nausea
  • nervousness
  • sensitivity to heat
  • shortness of breath
  • sweating
  • swelling of face, fingers, feet, or lower legs
  • troubled breathing
  • trouble sleeping
  • vomiting
  • weak pulse
  • weight gain
  • weight loss
  • wheezing

For Healthcare Professionals

Applies to liothyronine: compounding powder, intravenous solution, oral tablet


Reported side effects are usually indicative of excessive dosage and will usually disappear when the dose is reduced or treatment is stopped.[Ref]


Common (1% to 10%): Arrhythmia, tachycardia, cardiopulmonary arrest, hypotension, myocardial infarction

Frequency not reported: Angina, congestive heart failure, hypertension, flushing, palpitation[Ref]

Nervous system

Frequency not reported: Headache, tremor, benign intracranial hypertension[Ref]


Frequency not reported: Allergic skin reaction, sweating, rash pruritus, transient hair loss[Ref]


Frequency not reported: Twitching, muscle cramps, muscle weakness, craniostenosis, premature closure of epiphysis[Ref]


Frequency not reported: Diarrhea, vomiting[Ref]


Frequency not reported: Hypersensitivity reaction[Ref]


Frequency not reported: Phlebitis[Ref]


Frequency not reported: Restlessness, excitability, insomnia[Ref]


Frequency not reported: Menstruation irregular[Ref]


Frequency not reported: Fever, edema, weight loss, heat intolerance[Ref]


1. "Product Information. Cytomel (liothyronine)." Monarch Pharmaceuticals Inc, Bristol, TN.

2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

3. "Product Information. Triostat (liothyronine)." JHP Pharmaceuticals, Saddle River, NJ.

4. Cerner Multum, Inc. "Australian Product Information." O 0

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.