Levothyroxine

Levothyroxine is taken for an underactive thyroid gland.

How to buy Levothyroxine online

If you have already been prescribed Levothyroxine in the past but you are unable to access a prescription urgently, The Online Clinic may be able to help with a next day delivery service of this medication. Please complete our quick online consultation to start.

What is Levothyroxine?

The thyroid gland is situated in the neck, under the voice box (the larynx). It produces a hormone called thyroxine. Thyroxine controls the body's metabolism, which converts food into energy. When the thyroid gland does not produce enough thyroxine, the gland is underactive and the person has the condition hypothyroidism. Hypothyroidism causes a reduction in the body's metabolic rate, which in turn results in the rate of many body functions to decrease. Conversely, when the thyroid gland is overactive, the condition is known as hyperthyroidism that causes the rate of body functions to increase.

Levothyroxine is a man-made version of thyroxine, which is used treat people with hypothyroidism. It replaces the deficit in thyroxine caused by the underactive thyroid gland. Common symptoms of hypothyroidism include tiredness, feeling cold, weight gain, slow movements, depression, and constipation.

How to use Levothyroxine

Levothyroxine is available as anhydrous levothyroxine sodium in tablets and as an oral solution. There are three strengths of levothyroxine tablet, 25, 50 and 100 micrograms. The oral solution is formulated as levothyroxine 25, 50, and 100 micrograms per 5ml of oral solution. Adolescents and children are more likely to be prescribed the oral solution (not available via The Online Clinic).

Your doctor will tell you whether to take tablets or oral solution, and how much levothyroxine you need and when to change the dose. A child's dose with depend on their age or weight.

Adults usually start treatment on a dose of 50-100 micrograms daily. The dose may be increased by 50 micrograms every 3-4 weeks, up to a final dose of 100-200 micrograms daily, until the correct level of thyroxine is reached. However, the dose will differ for adults aged over 50 years, with a heart condition, severe hypothyroidism, diffuse non-toxic goitre, Hashimoto's thyroiditis, or with thyroid cancer. The dose will also differ for children, and will be dependent on their diagnosis, e.g., congenital hypothyroidism in infants, acquired hypothyroidism in children, and juvenile myxoedema.

Take this medicine before breakfast or the first meal of the day. Both the tablets and oral solution are swallowed. The tablets are taken with water. The box containing the oral solution contains a dosing pipette, graduated up to 10 ml, and a dosing adaptor. The correct dose of medicine is drawn up into the pipette and administered into the mouth.

Treatment is usually life-long if being taken for hypothyroidism, non-toxic diffuse goitre or Hashimoto's thyroiditis. You should not stop taking Levothyroxine unless you have been told to stop by a doctor.

You will need a blood test to calculate how much levothyroxine you need before you start taking levothyroxine. Then, you will need regular blood tests to check the dose of medicine is providing you with the correct blood thyroxine level. Tell the person taking the blood sample if you are taking or have recently taken biotin, multivitamins, or supplements as they can affect blood test results.

It is important to note that (1) you must take only the dose that your doctor has told you to take, because your thyroid gland could then produce too much thyroxine if the dose is too high (which may lead to osteoporosis - usually reversible once the dose is lowered or medicine stopped); (2) thyroid hormones are not to be used for weight reduction. Serious/life threatening side effects can occur if you increase your dose without asking a doctor; and (3) you may feel unwell if you switch to another brand of levothyroxine. Inform your doctor if this happens so that a blood test can check your thyroid hormone levels. You may need to have a particular levothyroxine brand.

Seek medical advice straight away or go to a hospital casualty department if you or a child takes too much levothyroxine. You may experience side effects, which sometimes appear up to 5 days later. If you forget to take a dose, then take it when you remember as long as it is not too near the time of the next dose. Never take the forgotten dose along with another dose; dismiss it. Forgetting to give a child their dose means that advice from a doctor or pharmacist must be sought.

Who can use Levothyroxine?

Levothyroxine may be taken by any person when their thyroid gland produces insufficient thyroxine. In cases of pregnancy, breastfeeding and planning a baby, get advice from your doctor as to whether to stop levothyroxine, particularly during months 1 to 3 of pregnancy.

People with an allergy to levothyroxine or any of the other constituents in the tablet, with an overactive thyroid gland (that produces too much levothyroxine), with a condition affecting the adrenal glands, myocardial infarction, myocarditis (inflammation of the heart muscle), or pancarditis (inflammation of the heart muscle) should not use levothyroxine. Also, pregnant women must not take both levothyroxine and antithyroid medicines (those opposing an overactive thyroid gland).

Before taking levothyroxine, inform the prescribing doctor if you are over aged 50 years, have had hypothyroidism for a long time; or have heart problems or high blood pressure, epilepsy, panhypopituitarism (a lack of all hormones produced by the pituitary gland), and/or diabetes.

Inform your doctor about all your medicines (i.e., those taken currently, recently, and could be taken in the future), including non-prescription medicines, vitamin supplements and herbal remedies. This is important because many different medicines affect the way in which levothyroxine works and levothyroxine affects the way in which other medicines work.

Levothyroxine side effects

Rarely, people can be allergic to levothyroxine and require medical attention, experiencing one or more of the following symptoms: difficulty breathing, severe skin itching with urticaria, sensitivity to the sun, swelling of their face, lips, tongue and throat, joint pain, and a general unwell feeling.

A "thyroid crisis" can occur, with symptoms including an irregular heartbeat, fast beating heart, heart failure, low blood pressure, very high temperature, jaundice, fits, confusion, and coma. This severe reaction indicates that your thyroid hormone levels are too high, and that you must see a doctor immediately.

Most side effects are like those occurring when too much thyroxine is produced (hyperthyroidism). Your dose of levothyroxine is too high, so contact your doctor as soon as possible for an adjustment of your dose (do not do this yourself). The symptoms usually disappear once your dose has been reduced or the tablets are stopped.

Side effects reported with levothyroxine include: headache, chest pain, fast or irregular heartbeat, flushing, high temperature, sweating, tremor, excitability, restlessness, insomnia, muscle cramps and/or weakness, hair loss, weight loss, vomiting, diarrhoea, and irregular periods.

Children and the very young starting levothyroxine may experience: craniostenosis in infants (early closure of joints in the skull leading to deformity); circulatory collapse in preterm neonates with very low birth weight (rapid fall in blood pressure; blood pressure is regularly monitored); benign intracranial hypertension in children (increased pressure around the brain); slow or no growth in children (due to altered bone growth); heat intolerance in children; and hair loss during the first few months of treatment in children (temporary and regrowth usually occurs).

References

Eltroxin® 50 and 100 micrograms Tablets. Mercury Pharma Group Ltd., London, EC2M 1QS, UK. Aug 2023.