Euthyrox - Precautions | Use | Dosage | Effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Euthyrox contains levothyroxine sodium - a synthetic thyroid hormone that is used to treat disorders of the thyroid gland function. It has the same effect as the natural hormones of the thyroid gland. It is used for the treatment of conditions where there is a deficit of thyroid hormones (goiter, thyroid cancer and other conditions that are characterized by low levels of thyroid hormones).

Sometimes high doses of Euthyrox (100 and 150 micrograms) are used for diagnostic purposes to evaluate the function of the thyroid gland.

Euthyrox exists at doses of 25 mcg, 50 mcg, 75 mcg, 100 mcg, 125 mcg and 150 mcg (mcg - microgram).


Use of Euthyrox is contraindicated in the following disorders:

  • Thyrotoxicosis (excessive secretion of thyroid hormones)
  • Heart problems (myocarditis, arrhythmias, hypertension, or heart attack), bearing in mind that these hormones have a powerful influence on the heart function
  • Impaired function of the adrenal glands

Caution should be taken in patients who have atherosclerosis - a condition that is characterized by the deposition of fats in blood vessels.

While you are being treated with this medication, you'll often need to check your thyroid hormone blood levels to avoid the risk of too high or too low levels of the thyroid hormones because it can affect your health.

Sometimes, unjustifiably, this medication is used for weight loss. Weight loss is a side effect of this drug and therefore it should never be applied for this purpose.

Euthyrox and its use during pregnancy and lactation

Euthyrox belongs to the class A, which means that it is safe for application during pregnancy. Your doctor will probably recommend that you continue taking this drug during pregnancy.

Euthyrox passes in very low concentrations into breast milk and can have non-significant effects on the baby.


According to the Euthyrox Patient Information Leaflet, the recommended dosage is as follows:

  • Treatment of goiter in patients having a normal thyroid function as well as for the prevention of goiter: 75 - 200 mcg per day
  • Suppression of thyroid tumor growth: 150 - 300 mcg daily
  • Balancing the levels of thyroid hormones: 50 - 100 mcg daily
  • Diagnostic purposes: 75 mcg twenty-eight days before the test and 200 mcg fourteen days before the test

The exact dosage depends primarily on the level of hormones in the blood which is determined by a simple blood test.

It is best to take Euthyrox pill in the morning before breakfast.

Interactions with other drugs and food

Euthyrox can affect the following drugs:

  • Oral hypoglycemic agents - medicines used to control blood sugar levels in diabetics. Euthyrox increases the effect of these drugs, which is why it is recommended to check your blood sugar levels more often than usual and to change the dose of anti-diabetic medications
  • Coumarin derivatives (Coumadin, warfarin and acenocoumarol) - the so-called blood thinners. Euthyrox increases the effect of these drugs which increases the risk of bleeding. This negative effect is particularly pronounced in the elderly.

Drugs that can affect Euthyrox include:

  1. Cholestyramine and colestipol - medicines for lowering blood lipid levels. These drugs can block the absorption of Euthyrox, and it is necessary to take Euthyrox 5-6 hours before you take cholestyramine or colestipol.
  2. Antacids (magnesium hydroxide, aluminum hydroxide, calcium carbonate, hydrotalcite, and others). These drugs also block the absorption of the Euthyrox and it is necessary to take Euthyrox 4 hours before taking antacid.
  3. Acetylsalicylic acid (Aspirin). Aspirin may increase the effect of Euthyrox and increase the risk of side effects.
  4. Fibrates (clofibrate, fenofibrate and others) - drugs that are used for hypertriglyceridemia treatment. These drugs may increase the effects of the Euthyrox which can lead to side effects.
  5. HIV medications

Other drugs that should not be used in combination with Euthyrox:

  • Sertraline - a drug used to treat depression, anxiety and social phobia
  • Propranolol, bisoprolol, carvedilol, atenolol and other beta blockers
  • Drugs for the treatment of malaria
  • Estrogen preparations

This list is not complete. Tell your doctor about all the medicines, herb products and OTC products you are taking.

Regarding the interaction with food, the only known interaction is with soy because soy can reduce the absorption of this drug and reduce its effectiveness. Make sure you do not eat soy while taking this medication.

Euthyrox unwanted effects

Possible Euthyrox side effects include:

  • Arrhythmias
  • Muscle weakness
  • Muscle cramps
  • Chest pain
  • A headache
  • Weight loss
  • Swelling of the eyes
  • Uncontrollable shaking
  • Allergic reaction

Tell your doctor if you notice any side effects.

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.

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