Who can and cannot take levothyroxine
Levothyroxine can be taken by adults and children. However, levothyroxine is not suitable for some people. Do not take levothyroxine and go back to your doctor to discuss your treatment if you have:
- had an allergic reaction to levothyroxine or any other medicines in the past
- an overactive thyroid (hyperthyroidism)
- a health problem that affects your adrenal glands (your doctor will be able to tell you if you’re not sure)
- a heart problem including angina, heart disease or heart failure
- high blood pressure
- had a heart attack
- diabetes – the dose of your diabetes medicine may need to change because levothyroxine can raise blood sugar levels
Some medicines can interfere with thyroid hormones, so the dose of levothyroxine may need to be changed. They include:
- medicines for fits or seizures – such as carbamazepine and phenytoin
- rifampicin
- amiodarone
- oestrogens – such as in combined contraceptive pills or hormone replacement therapy (HRT)
Levothyroxine can change how other medicines work, so their doses may need to be altered. These medicines include:
- medicines for diabetes – either insulin or tablets
- the blood thinning medicine, warfarin
Some medicines should not be taken at the same time of day as levothyroxine as they can reduce the amount of levothyroxine your body takes in, including:
- antacids
- calcium salts
- iron salts
- orlistat, a medicine used for weight loss
- sucralfate, a medicine used to treat stomach ulcers
- some cholesterol-lowering medicines such as colestyramine, colestipol or colesevelem
- Mixing levothyroxine with herbal remedies and supplements
Side effects
Like all medicines, levothyroxine can cause side effects, although not everyone gets them. Once you are on the right dose of levothyroxine, side effects should go away. The common side effects of levothyroxine usually happen because the dose you’re taking is more than you need. These side effects usually go away after you go on to a lower dose of levothyroxine or stop treatment. Common side effects are the same as the symptoms of an overactive thyroid. Talk to your doctor or pharmacist if these side effects bother you or do not go away.
- Feeling sick
- Being sick (vomiting) or diarrhoea
- Headaches
- Feeling restless or excitable, or problems sleeping
- Flushing or sweating
- Muscle cramps
- Shaking, usually of the hands
- Serious side effects
- chest pain
- fast or irregular heartbeats, or palpitations
- Serious allergic reaction
