If you're prescribed levothyroxine, you should take 1 tablet at the same time every day. It's usually recommended that you take the tablets in the morning, although some people prefer to take them at night.
The effectiveness of the tablets can be altered by other medications, supplements or foods, so they should be swallowed with water on an empty stomach, and you should avoid eating for 30 minutes afterwards.
If you forget to take a dose, take it as soon as you remember, if this is within a few hours of your usual time. If you don't remember until later than this, skip the dose and take the next dose at the usual time, unless advised otherwise by your doctor.
An underactive thyroid is a lifelong condition, so you'll usually need to take levothyroxine for the rest of your life.
If you're prescribed levothyroxine because you have an underactive thyroid, you're entitled to a medical exemption certificate. This means you don't have to pay for your prescriptions. See getting help with prescription costs for more information on this.
Levothyroxine doesn't usually have any side effects, because the tablets simply replace a missing hormone.
Tell your doctor if you develop new symptoms while taking levothyroxine. You should also let them know if your symptoms get worse or don't improve.
In the UK, combination therapy – using levothyroxine and triiodothyronine (T3) together – isn't routinely used because there's insufficient evidence to show it's better than using levothyroxine alone (monotherapy).
In most cases, suppressing thyroid-stimulating hormone (TSH) using high dose thyroid replacement therapy should be avoided because it carries a risk of causing adverse side effects, such as atrial fibrillation (an irregular and abnormally fast heart rate), strokes, osteoporosis and fracture.
However, this type of treatment may sometimes be recommended in cases where a person has a history of thyroid cancer and there's a significant risk of it reoccurring.
Underactive thyroid and pregnancy
It's important for the health of you and your baby that an underactive thyroid is treated properly before you become pregnant.
Tell your GP if you're pregnant or trying to become pregnant and you have hypothyroidism. They may refer you to a specialist for treatment and monitoring during your pregnancy.