Synthroid Side Effects
Although most people have no problems when taking Synthroid, it is possible for side effects to occur. Examples of common side effects include heart palpitations, difficulty breathing, and chest pain. Because some of these side effects can be quite dangerous, be sure to immediately report any side effects of Synthroid to your healthcare provider, as he or she may need to adjust your dosage.
As with any medicine, side effects are possible with Synthroid® (levothyroxine sodium). However, not everyone who takes the drug will have problems. In fact, most people tolerate it quite well. If side effects do occur, in most cases, they are minor and either require no treatment or can easily be treated by you or your healthcare provider.
(This article covers many, but not all, of the possible side effects with Synthroid. Your healthcare provider can discuss a more complete list of Synthroid side effects with you.)
Synthroid side effects typically occur when the dose is too high. Too much thyroid hormone causes symptoms of an overactive thyroid (hyperthyroidism). Some of these symptoms can be quite dangerous, and any of these symptoms should be reported to your healthcare provider, as they may signal that your Synthroid dosage needs to be adjusted. These side effects include:
- An increased appetite, along with weight loss
- Feeling hot all the time and increased sweating
- Hyperactivity, nervousness, anxiety, or irritability
- Insomnia (see Synthroid and Insomnia)
- Emotional changes
- Shakiness or muscle weakness
- Heart palpitations
- High blood pressure (hypertension)
- A rapid heart rate (tachycardia)
- Heart failure, chest pain, or a heart attack
- Difficult or painful breathing
- Diarrhea, vomiting, or abdominal cramps (stomach cramps)
- Hair loss (see Synthroid and Hair Loss)
- Broken bones or other signs of weakened bones
- Menstrual problems or fertility problems
As with any medication, Synthroid can also cause allergic reactions. Seek medical attention immediately if you develop signs of an allergic reaction, including:
- An unexplained rash
- Unexplained swelling (especially of the lips, mouth, or throat).