Euthyrox tablets 25–150 micrograms – levothyroxine for hypothyroidism and thyroid disorders

Euthyrox contains levothyroxine sodium, a synthetic thyroid hormone with the same action as the natural thyroid hormones. It is used to treat diseases and disorders of thyroid function.

In Serbia it is authorised in nine strengths – 25, 50, 75, 88, 100, 112, 125, 137 and 150 micrograms – so that the doctor can set the individual dose precisely. Most patients take it for life.

What is Euthyrox used for and how should it be taken correctly?

Key facts about the medicine

What is Euthyrox used for?

• treatment of benign goitre (enlarged thyroid) in patients with normal thyroid function;
• prevention of goitre recurrence after surgery;
• replacement of natural hormones when the thyroid does not produce enough (hypothyroidism);
• suppression of tumour growth in patients with thyroid cancer;
• according to the SmPC, also restoring hormone balance alongside antithyroid medicines in overactive thyroid.

How is it used and dosed?

The doctor sets the individual dose based on examination and laboratory results. Treatment usually starts with a low dose increased every 2–4 weeks, with follow-up tests. Range of usual daily doses according to the leaflet:

• Take the whole daily dose in the morning on an empty stomach, at least half an hour before breakfast, with a little liquid (e.g. half a glass of water).
• Children are given the whole daily dose at least half an hour before the first meal: crush the tablet just before use, mix with a little water and give with some more liquid; always prepare the mixture fresh.
• For newborns with congenital hypothyroidism, the recommended starting dose is 10–15 micrograms per kilogram body weight for the first 3 months, after which the dose is adjusted.
• Lower doses may be sufficient in older people, those with heart problems, severe or long-standing hypothyroidism, low body weight or a large goitre.
• The length of treatment depends on the condition; most patients take the medicine for life.

Special patient groups

• Older people and heart patients: lower doses may be sufficient; treatment is started cautiously with frequent hormone checks.
• Newborns and children: rapid replacement is important in congenital hypothyroidism; in newborns with very low birth weight blood pressure is monitored because of a possible sudden drop (circulatory collapse).
• Women in menopause and postmenopause: the doctor may check thyroid function regularly because of the risk of osteoporosis.
• Switching medicines: changing to another levothyroxine medicine may upset hormone balance – careful monitoring is needed.

Contraindications – when the medicine must not be used

Do not take Euthyrox:

• if you are allergic to levothyroxine sodium or any of the ingredients;
• if you have untreated adrenal or pituitary insufficiency, or untreated overactive thyroid (thyrotoxicosis);
• if you have an acute heart condition such as myocardial infarction or inflammation of the heart muscle (myocarditis).

During pregnancy, Euthyrox must not be taken together with antithyroid medicines.

Warnings and precautions

Talk to your doctor before starting treatment if you have angina, heart failure, fast and irregular heartbeat, high blood pressure or arteriosclerosis – these conditions must be under control before treatment starts, and hormone levels must be checked frequently. The doctor will also check adrenal and pituitary function and whether thyroid autonomy is present.

• Tell your doctor before starting or stopping orlistat (a weight-loss medicine) and if you notice signs of psychotic disorders.
• High doses of thyroid hormones should not be taken together with weight-loss medicines such as amfepramone, cathine and phenylpropanolamine.
• Biotin (vitamin H, B7 or B8) may falsely raise or lower hormone test results – the doctor may ask you to stop it before testing.
• The medicine contains less than 1 mmol (23 mg) sodium per dose, i.e. it is essentially "sodium-free".

Interactions with other medicines, food and drink

• Euthyrox changes the effect of other medicines: it may reduce the effect of diabetes medicines (more frequent blood sugar checks) and increase the effect of coumarin anticoagulants (risk of bleeding, clotting checks).
• Time interval: take colestyramine and colestipol 4–5 hours after Euthyrox; antacids, sucralfate and products with aluminium, iron or calcium at least 2 hours after the medicine.
• Reduce the effect of Euthyrox: propylthiouracil, glucocorticoids, beta-blockers, sertraline, chloroquine, proguanil, barbiturates, carbamazepine, St John's wort, oestrogen-containing medicines (hormone therapy, contraception), sevelamer, tyrosine kinase inhibitors, proton pump inhibitors (omeprazole, esomeprazole, pantoprazole, rabeprazole, lansoprazole) and orlistat.
• Increase the effect: salicylates, dicoumarol, high-dose furosemide (250 mg), clofibrate.
• May affect the effect: ritonavir, indinavir, lopinavir, phenytoin; amiodarone and iodinated contrast media may affect thyroid function.
• Food: soy products may reduce absorption of the medicine – tell your doctor if you use them or change the amount.

Pregnancy and breast-feeding

• Pregnancy: continue taking Euthyrox and contact your doctor, as a dose change may be needed. If you took it together with antithyroid medicines, your doctor will advise stopping Euthyrox when you become pregnant.
• Breast-feeding: continue treatment as advised – the amount in breast milk is so small that it will not affect the child.

Driving and using machines

No effect on the ability to drive and use machines is expected, because levothyroxine is identical to the natural thyroid hormone.

Possible side effects

If the dose is too high or the prescribed dose is not tolerated (e.g. with a rapid increase), the following may occur: irregular or fast heartbeat, chest pain, headache, muscle weakness or cramps, flushing, fever, vomiting, menstrual disturbances, pseudotumour cerebri (increased pressure in the head), tremor, restlessness, sleep disturbance, sweating, weight loss and diarrhoea. Contact your doctor – they may stop treatment for a few days or reduce the dose.

Allergic reactions to the ingredients are possible – rash, hives and swelling of the face or throat (angioedema); if this happens, contact your doctor immediately.

Overdose, missed dose and stopping treatment

• Overdose: fast heartbeat, anxiety, agitation or involuntary movements may occur; in epilepsy, in isolated cases convulsions, and in people at risk of psychotic disorders, symptoms of acute psychosis. Contact your doctor.
• Missed dose: do not take a double dose – take your normal dose the next day.
• Stopping treatment: treatment is usually lifelong; the doctor decides the dose and duration.

Related information

For questions about thyroid treatment, spacing between the medicine and supplements (calcium, iron, magnesium, biotin) and hormone check-ups, contact your doctor or pharmacist.

Composition, pack and manufacturer

• Active substance: levothyroxine sodium – 25, 50, 75, 88, 100, 112, 125, 137 or 150 micrograms per tablet.
• Excipients: maize starch; anhydrous citric acid; croscarmellose sodium; gelatin; magnesium stearate; mannitol (E421).
• Pack: box with 2 PVC/Alu blisters of 25 tablets (50 tablets).
• Marketing authorisation holder: Merck d.o.o. Beograd, Omladinskih brigada 90v, Belgrade – Novi Beograd. Manufacturer: Merck Healthcare KGaA, Darmstadt, Germany.

Storage

• Store below 25 °C, in the original package to protect from light.
• Keep out of the sight and reach of children.
• Shelf life is 3 years; do not use after the expiry date. Return unused medicine to a pharmacy that collects unused medicines.

Frequently asked questions

How should Euthyrox be taken?

Take the whole daily dose in the morning on an empty stomach, at least half an hour before breakfast, with a little liquid (e.g. half a glass of water). For children, the tablet is crushed, mixed with a little water and given at least half an hour before the first meal.

Can I take calcium or iron with Euthyrox?

Yes, but not at the same time. According to the leaflet, Euthyrox should be taken at least 2 hours before antacids, sucralfate and products with aluminium, iron or calcium, and 4–5 hours before colestyramine or colestipol, as they may reduce its effect.

Does Euthyrox help with weight loss?

No. The leaflet clearly states that thyroid hormones must not be used to reduce body weight – with normal hormone levels they do not reduce weight, and increasing the dose without medical advice may cause serious or even life-threatening side effects.

May I take Euthyrox during pregnancy and breast-feeding?

Yes – treatment continues during pregnancy and the doctor may change the dose. During breast-feeding the medicine is taken as advised, because the amount in milk is too small to affect the child. The exception is the combination with antithyroid medicines, which is not used in pregnancy.

Sources

• ALIMS – Summary of Product Characteristics, Euthyrox® tablets 25–150 micrograms (SmPC, Serbian, September 2023, all strengths)
• ALIMS – Package leaflet, Euthyrox® 112 micrograms tablets (PIL, Serbian, September 2023)
• ALIMS – Package leaflet, Euthyrox® 100 micrograms tablets (PIL, Serbian, May 2023)

Sources checked on: 25 October 2026.