An underactive thyroid (hypothyroidism) is usually treated by taking hormone-replacement tablets called levothyroxine.
Levothyroxine replaces the thyroxine hormone which your thyroid does not make enough of.
A blood test measuring your levels of thyroid-stimulating hormone (TSH) will establish how much levothyroxine you need.
If the test detects high levels of TSH, it means you have an underactive thyroid and your doctor may advise you to take levothyroxine.
You may start on a low dose of levothyroxine, which may be increased gradually depending on how your body responds.
You will initially have regular blood tests until the correct dose of levothyroxine is reached. This can take a little while to get right.
If your symptoms are mild
If testing detects high levels of TSH but you do not have any symptoms or they are very mild, you may not need any treatment.
Your GP will usually monitor your hormone levels every few months and may start you on levothyroxine if you develop symptoms.
Some people start to feel better soon after beginning treatment, while others can take several months.
An underactive thyroid is a lifelong condition, so you will probably need to take levothyroxine for the rest of your life.
Levothyroxine does not usually have any side effects as the tablets simply replace a missing hormone.
Once you are taking the correct dose, you will usually have a blood test once a year to monitor your TSH levels.
Find out about the complications of an underactive thyroid.
