Side effects
Levothyroxine can have side effects, but not everyone experiences them. This is true of all medications. The side effects of levothyroxine should disappear once you are taking the recommended dosage.
If you have changed to a different brand of levothyroxine and begin to experience any of the following symptoms:
- symptoms of an underactive thyroid including feeling tired, weight gain, or feeling depressed
- symptoms of an overactive thyroid
You might need to stick with the brand of levothyroxine you were previously taking if you are sensitive to the new one your doctor has prescribed.
Common side effects
The most common side effects of levothyroxine occur when the dose is higher than necessary. These side effects usually go away after you reduce your levothyroxine dose or discontinue treatment.
The most common side effects are similar to the symptoms of an overactive thyroid. There are things you can do to help yourself cope.
- Feeling sick (nausea)
- Being sick (vomiting)
- Diarrhoea
- Headaches
- Feeling restless or excitable, or problems sleeping
- Flushing or sweating
- Muscle cramps
- Shaking, usually of the hands
If these side effects bother you or do not go away, consult your doctor or pharmacist.
Serious allergic reaction
Rarely, but still possible, some people who take levothyroxine may experience severe side effects. If you experience rapid or irregular heartbeats (palpitations), call 111 or your doctor right away. 111.nhs.uk or 111 can be contacted Levothyroxine can, on occasion, cause a severe allergic reaction (anaphylaxis). Levothyroxine has additional side effects in addition to these. See the leaflet inside your medicine packet for a complete list.
