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Apr 8, 2024

Euthyrox vs Levothyroxine: Which is better?


The thyroid gland is in your neck, below the Adam’s apple, and in front of the trachea (windpipe). It plays an important role in regulating metabolism and energy production in the body.

It produces 2 main hormones: thyroxine (T4) and triiodothyronine (T3). These hormones are essential for maintaining various bodily functions, including heart rate, digestion, and temperature regulation.

T4 is the most abundant thyroid hormone produced by your thyroid gland. It is synthesized by combining iodine and the amino acid tyrosine. T4 is relatively inactive compared to T3 but serves as a precursor for T3.

T3 is the more active form of thyroid hormone. It is produced in smaller quantities compared to T4 but is more potent. T3 is formed either directly by your thyroid gland or through the conversion of T4 into T3 in peripheral tissues, such as the liver and kidneys.

The production of T4 and T3 is controlled by the pituitary gland in the brain, which releases thyroid-stimulating hormone (TSH) to signal the thyroid to produce more hormones when needed.

The balance between T4 and T3 levels is essential for maintaining normal bodily functions, and disruptions in their levels can lead to various health problems, including hypothyroidism or hyperthyroidism.


Hypothyroidism occurs when your thyroid gland doesn't produce enough T4 and T3 hormones, leading to a slowdown in metabolism and various symptoms such as fatigue, weight gain, sensitivity to cold, dry skin, and hair loss.

With an estimated prevalence of around 4.6% in the United States, hypothyroidism is a relatively common endocrine disorder. It can arise from various factors such as autoimmune diseases like Hashimoto’s thyroiditis, thyroid surgery, radiation therapy, iodine deficiency, or certain medications.

While hypothyroidism can affect people of all ages, it's most frequently diagnosed in women over 60.

Hormone Replacement Therapy

The standard treatment for hypothyroidism involves hormone replacement therapy that restores thyroid hormone levels and alleviates symptoms.

Two commonly prescribed medications are EUTHYROX and Levothyroxine. Understanding the distinctions between the two drugs can help you make an informed decision about the most suitable treatment option for your condition.


EUTHYROX and Levothyroxine are primarily used for managing hypothyroidism in both pediatric and adult patients.

    • Approved for use in both pediatric and adult patients for replacement therapy in congenital or acquired hypothyroidism.
    • Can be prescribed for certain cases of goiter caused by hypothyroidism, which may result from hormonal imbalances, radiation therapy, surgical interventions, or cancer.
  • Levothyroxine:
    • Prescribed for both adults and children to manage hypothyroidism.
    • In adults, used in conjunction with surgical procedures and radioactive iodine therapy for the treatment of specific forms of thyroid cancer.

Both medications provide the same active ingredient, levothyroxine sodium, and are often used interchangeably depending on availability and physician preference.

Administration and Dosage
    • Take the medication once daily on an empty stomach, preferably 30 minutes to 1 hour before breakfast. Swallow the tablet whole with a full glass of water.
    • Dosage: 25 mcg to 200 mcg
  • Levothyroxine:
    • Take the medication once daily on an empty stomach, either at least 60 minutes before breakfast or at bedtime, which should be at least 3 hours after your last meal. Take it with water.
    • Dosage: 13 mcg to 300 mcg

Side Effects

EUTHYROX and Levothyroxine contatin the same active ingredient and share a similar safety profle. Some common side effects include:

  • Headaches, leg cramps, muscle pain or weakness
  • Anxiety, nervousness, irritability
  • Chest pain
  • Irregular heartbeats
  • Difficulty sleeping (insomnia)
  • Increased appetite
  • Weight loss
  • Increased sweating or feeling hot
  • Diarrhea or vomiting
  • Stomach cramps
  • Changes in menstrual periods
Warnings associated with Levothyroxine
  • Cardiovascular risk: Levothyroxine therapy may increase the risk of cardiovascular events, particularly in elderly patients or those with preexisting heart disease.
  • Adrenal crisis: Levothyroxine treatment in patients with adrenal insufficiency may exacerbate symptoms.
  • Worsening diabetes: Levothyroxine therapy may alter glucose metabolism, and can increase your blood sugar levels, especially when you first start this medication and when your doctor increases your dose and needs adjustment of antidiabetic medication dosage in patients with diabetes mellitus.
Caution and Warning associated with EUTHYROX
  • Caution: Euthyrox is not intended for obesity treatment or weight loss.
    Thyroid hormones, such as Euthyrox, whether used alone or with other medications, should not be used to treat obesity or weight loss. In those with normal thyroid function, doses within the range of daily hormonal requirements are ineffective for weight loss. Administering larger doses may lead to severe or potentially life-threatening side effects.
  • Warning: Euthyrox has a narrow therapeutic index.
    Incorrect dosing, whether excessive or insufficient, may result in adverse problems affecting various aspects of your health, including growth, cardiovascular health, bone metabolism, reproductive function, cognitive abilities, emotional well-being, gastrointestinal function, as well as glucose and lipid metabolism in both adult and pediatric individuals.

EUTHYROX vs Levothyroxine

While both EUTHYROX and Levothyroxine contain the same active ingredient, there are differences worth noting.

Packaging Matters

Euthyrox comes in blister packs designed to shield it from light, oxygen, and moisture. This packaging helps maintain its potency better compared to generic Levothyroxine, which is often dispensed in bottles, making it more vulnerable to environmental factors. Studies suggest that Levothyroxine stored in bottles may lose effectiveness within 30 days.

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Potency and Precision

All manufacturers of Levothyroxine must ensure their product falls within a potency range mandated by the FDA, allowing for a maximum 5% variance. However, even minor discrepancies in potency can accumulate over time, potentially affecting treatment outcomes. This narrow therapeutic window requires precise adjustments to achieve optimal results.

Switching Brands

Transitioning from one brand to another or from a brand to a generic formulation may lead to noticeable differences in how you feel on the medication. These changes could impact thyroid function tests, so it's essential to make any switches under the guidance of your healthcare provider.

Speak With Your Doctor

You should discuss with your doctor whether to take EUTHYROX or Levothyroxine as both are effective medications for thyroid hormone replacement therapy in hypothyroidism. The choice between the two hinges on factors such as your medical history, lifestyle preferences, and guidance from your healthcare provider. By considering these factors and consulting with your healthcare provider, you can determine which medication option aligns best with your needs and circumstances.