All medicines may cause side effects, but many people have no, or minor, side effects. No COMMON side effects have been reported with the use of Synthroid. Seek medical attention right away if any of these SEVERE side effects occur when using Synthroid:
- Severe allergic reactions (rash; hives; itching; difficulty breathing; flushing; tightness in the chest; swelling of the mouth, face, lips, or tongue; unusual hoarseness); changes in appetite; changes in menstrual periods; chest pain; diarrhea; excessive sweating; fast or irregular heartbeat; fever; heat intolerance; joint pain; leg cramps; mental or mood changes (eg, anxiety, irritability, nervousness); muscle weakness; seizures; severe or persistent headache or fatigue; shortness of breath; stomach cramps; tremors; trouble sleeping; unusual weight gain or weight loss; vomiting; wheezing.
fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating;
Central nervous system
headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia
menstrual irregularities, impaired fertility
This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects.