Levothyroxine sodium is a thyroid hormone that replaces or adds to the natural thyroid hormones normally produced by the thyroid gland. Thyroid hormones help in many body functions related to growth and energy.
This medicine is used to treat thyroid deficiency due to an underactive thyroid gland.
Levothyroxine sodium may also be used together with surgery or radioiodine therapy to manage a certain type of thyroid cancer.
This medicine may be used to treat other conditions as decided by your doctor.
Take Levothyroxine sodium exactly as directed by your doctor or according to the instructions on the label. Do not take more or less than instructed by your doctor.
Take this medicine on an empty stomach, at least 30 to 60 minutes before breakfast or the first meal of the day. Try to take it at the same time each day.
Levothyroxine sodium is available as a tablet, capsule, or oral solution.
If you are taking the tablet, swallow it whole with a glass of water. Available brands of tablets may or may not be crushed and dissolved in water. Check with your doctor or pharmacist first if you are not sure how to take your medicine.
If you are taking the capsule, swallow it whole. Do not divide, crush, or chew the capsule.
If you have been given the oral solution, use the pipette (dropper) supplied with each bottle to measure out your dose. Refer to the package insert for directions on how the dropper should be used.
The dose of this medicine will be decided by your doctor. Your doctor will advise you on the treatment timeframe depending on the type and severity of your condition and your response to the medication.
Levothyroxine sodium must be taken regularly for it to be effective. Continue taking this medicine even when you feel better. Do not stop taking it unless instructed by the doctor.
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and return to your normal dosing schedule.
DO NOT double a dose under any circumstances.
If you often forget to take your medicine, let your doctor and pharmacist know.
Alert your doctor if you have the following conditions:
- excessive thyroid hormones in the blood
- problem with your adrenal glands which has not been treated
- history of heart attack
- inflammation of the heart muscle or the sac surrounding the heart
as Levothyroxine sodium may not be suitable for you.
Inform your doctor if you have any of the following conditions:
- heart disease or problems in the blood vessels e.g. coronary artery disease (narrowing of the blood vessels of the heart), high blood pressure, chest pain
- underactive adrenal glands
- epilepsy (fits or seizures)
Let your doctor know if you are pregnant or breastfeeding.
Be sure to check with your doctor or pharmacist before giving Levothyroxine sodium to a child or the elderly. Children and elderly people may be more sensitive to the side effects.
Do not switch brands unless instructed by your doctor. This is because different brands of this medicine may have slightly different ways of working in your body.
Why is it important to keep my appointments with the doctor?
Keep your appointments with your doctor. Your doctor needs to monitor your condition and check your response to the medication regularly.
- Routine tests (e.g. thyroid and renal function, bone mineral density) may be done while you are being treated with this medicine. Your doctor will advise you about how often you need to have these tests.
- Your doctor may also perform an ECG (test used to record the electrical activity of the heart) before starting the treatment.
- Your blood pressure may rise to unsafe levels without you noticing it. Monitor your blood pressure and heart rate during treatment.
- Children taking Levothyroxine sodium may need to have their growth and development checked regularly.
Levothyroxine sodium may cause any of the following side effects: headache, diarrhoea, vomiting, stomach pain, increased appetite, weight loss, nervousness, tremors, restlessness, difficulty sleeping, irregular menstruation, flushing, sweating, heat intolerance, muscle weakness or cramps, and temporary and partial hair loss.
Some side effects may need immediate medical help. Alert your doctor quickly if you experience any of the following:
- fast or irregular heartbeat, chest pain, very high temperature, confusion
- fits or seizures
- bone pain
Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.
Inform your doctor and pharmacist if you are taking any of these medicines:
- medicines to treat depression e.g. amitriptyline, sertraline
- blood-thinning medicines e.g. warfarin
- medicines for irregular heartbeat e.g. digoxin, amiodarone, propranolol
- medicines for epilepsy e.g. phenytoin, carbamazepine, phenobarbital, primidone
- NSAIDs (medicines for pain and inflammation) e.g. aspirin, phenylbutazone
- rifampicin (medicine to treat TB, lung infection known as tuberculosis)
- orlistat (medicine for obesity)
- cimetidine (medicine that reduces excess stomach acid)
- sevelamer (medicine used to lower phosphorus levels)
This list does not include all medicines that may interact with Levothyroxine sodium.
This medicine should not be taken with colestyramine, colestipol, antacids, or supplements containing calcium, iron, or aluminium as these medicines could reduce the absorption of Levothyroxine sodium. If you must take these medicines, take Levothyroxine sodium at least 4 hours before taking your dose of the other medicines.
Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics such as traditional Chinese medicine, supplements and medicines that you buy without a prescription.
Avoid alcohol and grapefruit juice.
Inform your doctor and pharmacist if you are taking soy-containing products, cottonseed meal, walnuts, and high dietary fibre.
Store in a cool, dry place away from the reach of children.
Protect from heat, moisture, and light.
Medicines must not be used past the expiry date.