Levothyroxine starts working straight away, but it may be several weeks before your symptoms start to improve.
The most common side effects of levothyroxine are caused by taking a bigger dose than you need. Your doctor can lower your dose to help reduce any side effects.
Before you start taking levothyroxine, your doctor will do a blood test to see what dose you need. Once you start taking the medicine you’ll have regular blood tests to see how well it’s working.
Levothyroxine doses need to be carefully monitored during pregnancy. If you’re planning to become pregnant or think you may be pregnant while taking levothyroxine, it’s important to visit your doctor to make sure you get the correct care for you and your baby.