An overactive thyroid (hyperthyroidism) can cause a wide range of symptoms, although it's unlikely you'll experience all of them.
The symptoms may develop gradually or suddenly. For some people they're mild, but for others they can be severe and significantly affect their life.
Symptoms of an overactive thyroid can include:
An overactive thyroid can also cause the following physical signs:
See a GP if you have symptoms or signs of an overactive thyroid. It might be useful to make a list of all your symptoms and show it to a GP.
These symptoms and signs can have a number of causes. But a blood test can often help to determine whether they're caused by a thyroid problem.
Find out more about how an overactive thyroid is diagnosed.