Synthroid Side Effects

What are Synthroid side effects?

Side effects are physical, mental or emotional symptoms which occur in addition to or outside of the desired effect of a therapeutic treatment such as an over-the-counter or prescribed drug or medication. Side effects from Synthroid may occur at the beginning or at the end of treatment and may also depend on the length of time an individual remains on the treatment. Side effects, also known as adverse effects, are generally more likely to occur when starting treatment. Individuals may also experience side effects from Synthroid as a result of an interaction with other medications.

Side Effects of Synthroid

The side effects of Synthroid may vary in number and intensity for many different reasons. Factors such as age, weight, gender and ethnicity may influence the side effects of Synthroid. Also, an individual’s state of general physical health and seriousness of the disease or illness as well as an increase or decrease in dosage may lead to side effects. Further, side effects from Synthroid may also occur as a result of an interaction with certain herbal supplements, foods or drinks.

Prescription drug side effects can be serious and may cause patients to stop the treatment. However, when side effects from the use of a prescription drug, such as Synthroid, do occur a patient should consult their physician. A physician may prescribe an additional treatment in order to control the symptoms or an adjustment in the dosage may be made. In addition, changes to diet, exercise or other lifestyle activities may help to lessen the side effects of Synthroid.

By understanding side effects and the factors which may influence the occurrence of side effects patients are empowered to take an active role in their care. Patients who have specific questions about the side effects of Synthroid, or any other medication, should contact their physician. General information about Synthroid and the side effects associated with Synthroid are described in the following:

Common Synthroid Side Effects


Less Severe

  • female infertility

Less Frequent Synthroid Side Effects


  • osteopenia

Less Severe

  • hypertension
  • weight loss

Rare or Very Rare Synthroid Side Effects


  • mood changes
  • idiopathic intracranial hypertension
  • acute myocardial infarction
  • angina
  • cardiac arrest
  • cardiac arrhythmia
  • heart failure
  • allergic dermatitis
  • urticaria
  • seizure disorder
  • skin rash
  • dyspnea
  • angioedema
  • abnormal hepatic function tests
  • tachycardia

Less Severe

  • symptoms of anxiety
  • irregular menstrual periods
  • alopecia
  • muscle weakness
  • fever
  • fatigue
  • hyperhidrosis
  • tremors
  • Flushing
  • Increased Appetite
  • insomnia
  • heat intolerance
  • palpitations
  • Pulse Changes
  • vomiting
  • diarrhea
  • Abdominal Pain with Cramps
  • Nervousness
  • Irritability
  • headache disorder
  • muscle spasm
  • menstrual disorder