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Levothyroxine: Dosage, Side Effects & Guide to Thyroid Medication
Summary of Key Points
Levothyroxine is a thyroid medication commonly prescribed to treat conditions such as hypothyroidism, Hashimoto’s thyroiditis, and thyroid cancer. It works by replacing or supplementing the thyroid hormone your body needs to function properly. Typically, Levothyroxine is taken once daily and should always be used as directed by your healthcare provider. Common side effects may include weight changes, heart palpitations, and fatigue. It is important to consult your doctor before making any adjustments to your Levothyroxine dosage.
Names of Thyroid Medication
Synthroid (Levothyroxine)
Levoxyl (Levothyroxine)
Unithroid (Levothyroxine)
Euthyrox (Levothyroxine)
Tirosint (Levothyroxine)
The generic name, Levothyroxine, is the active ingredient in these medications, listed in parentheses next to the brand name.
Pharmacologic Category
Thyroid Hormone Replacement
Levothyroxine Dosage
Levothyroxine is used to manage various thyroid-related conditions. The dosage and frequency depend on the specific condition being treated. Always consult your doctor before making any changes to your thyroid medication.
Levothyroxine Dosage for Hypothyroidism
Initial Dose: 1.6 mcg/kg/day, taken once daily.
Maintenance Dose: Adjust based on thyroid function tests. The typical maintenance dose ranges from 100 to 125 mcg/day.
Levothyroxine Dosage for Hashimoto’s Thyroiditis
Initial Dose: 1.6 mcg/kg/day, taken once daily.
Maintenance Dose: Adjust based on thyroid function tests. The typical maintenance dose ranges from 100 to 125 mcg/day.
Levothyroxine Dosage for Thyroid Cancer
Initial Dose: 2 mcg/kg/day, taken once daily.
Maintenance Dose: Adjust based on thyroid function tests and clinical response.
Levothyroxine Dosage for Goiter
Initial Dose: 50 to 100 mcg/day, taken once daily.
Maintenance Dose: Adjust based on thyroid function tests and clinical response.
Levothyroxine Dosage for Congenital Hypothyroidism
Initial Dose: 10 to 15 mcg/kg/day, taken once daily.
Maintenance Dose: Adjust based on thyroid function tests and clinical response.
Levothyroxine Dosage for Myxedema Coma
Initial Dose: 200 to 500 mcg IV once, followed by 100 to 300 mcg IV on day 2, then 50 to 100 mcg IV daily until the patient can switch to oral therapy.
Levothyroxine Dosage for Pituitary Gland Disorders
Initial Dose: 1.6 mcg/kg/day, taken once daily.
Maintenance Dose: Adjust based on thyroid function tests and clinical response.
Levothyroxine Dosage for Thyroid Hormone Deficiency
Initial Dose: 1.6 mcg/kg/day, taken once daily.
Maintenance Dose: Adjust based on thyroid function tests and clinical response.
Levothyroxine Dosage for Iodine Deficiency
Initial Dose: 1.6 mcg/kg/day, taken once daily.
Maintenance Dose: Adjust based on thyroid function tests and clinical response.
Levothyroxine Dosage for Thyroiditis
Initial Dose: 1.6 mcg/kg/day, taken once daily.
Maintenance Dose: Adjust based on thyroid function tests and clinical response.
Dosage Forms and Strengths
Levothyroxine is available in several forms and strengths, including:
- Tablets: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg
- Capsules: 13 mcg, 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg
- Oral Solution: 25 mcg/5 mL, 50 mcg/5 mL, 100 mcg/5 mL
- Injection: 200 mcg, 500 mcg (for IV use)
How to Take Levothyroxine Correctly
Levothyroxine should be taken on an empty stomach, ideally 30 to 60 minutes before breakfast. Swallow the tablet or capsule whole with a full glass of water. Avoid taking antacids, calcium supplements, or iron supplements within 4 hours of taking Levothyroxine, as these can interfere with its absorption. If you miss a dose, take it as soon as you remember, unless it is close to the time for your next dose. Do not take two doses at once.
Levothyroxine Side Effects
Like all medications, Levothyroxine can cause side effects. While most are mild, some may be more serious. If you experience any of the following, contact your healthcare provider immediately.
Common Levothyroxine Side Effects: These may include headaches, weight changes, increased appetite, and nervousness.
Less Common Side Effects: These may include hair loss, muscle weakness, and menstrual changes.
Serious Side Effects: These may include chest pain, rapid or irregular heartbeat, shortness of breath, or swelling of the legs and feet. Seek medical attention immediately if you experience any of these symptoms.
Contraindications for Levothyroxine
A contraindication is a specific condition or situation where a particular medication should not be used because it may cause harm. For Levothyroxine, several contraindications should be considered before starting treatment, including:
Untreated adrenal insufficiency: Levothyroxine can increase the body’s demand for cortisol, worsening adrenal insufficiency. This condition must be treated before starting Levothyroxine.
Thyrotoxicosis (overactive thyroid): Levothyroxine increases thyroid hormone levels, so taking it when your thyroid is already overactive can lead to dangerous complications, such as heart problems.
Acute myocardial infarction (heart attack): Levothyroxine can increase the heart’s workload, which may worsen heart conditions, especially after a heart attack.
Hypersensitivity to Levothyroxine or its ingredients: If you have a known allergy to Levothyroxine or any of its inactive ingredients, you should not take this medication.
If you have any of these conditions, it’s important to discuss them with your healthcare provider before starting Levothyroxine. If you’re unsure, one of our providers can assist you through a telemedicine consultation.
Drug Interactions with Levothyroxine
Levothyroxine can interact with several medications, which may affect how well it works or increase the risk of side effects. Some common drug interactions include:
Calcium supplements: (Caltrate, Tums) – Calcium can interfere with the absorption of Levothyroxine, reducing its effectiveness. It’s recommended to take these supplements at least 4 hours apart from Levothyroxine.
Iron supplements: (Ferrous sulfate, Fer-In-Sol) – Like calcium, iron can also reduce the absorption of Levothyroxine. These should be taken at least 4 hours apart.
Cholestyramine: (Questran) – This medication can bind to Levothyroxine in the stomach and reduce its absorption.
Warfarin: (Coumadin) – Levothyroxine can increase the effects of blood thinners like Warfarin, which may require dose adjustments to prevent bleeding complications.
Antacids: (Maalox, Mylanta) – These can interfere with Levothyroxine absorption if taken too close together.
Anti-seizure medications: (Phenytoin, Carbamazepine) – These can increase the metabolism of Levothyroxine, potentially lowering its effectiveness.
Always inform your healthcare provider about all the medications and supplements you’re taking. If you’re unsure about potential interactions, you can discuss this with one of our telemedicine providers.
Levothyroxine in Pregnancy
Is it safe to take Levothyroxine when pregnant? Yes, Levothyroxine is not only safe but often essential during pregnancy. Thyroid hormone plays a critical role in your baby’s development, particularly in brain growth. If you have hypothyroidism, your doctor may adjust your Levothyroxine dosage to ensure both you and your baby receive adequate thyroid hormone. It’s important to work closely with your healthcare provider to regularly monitor your thyroid levels throughout your pregnancy.
Levothyroxine while Breastfeeding
Is it safe to take Levothyroxine while breastfeeding? Yes, Levothyroxine is generally considered safe while breastfeeding. Only minimal amounts of the medication pass into breast milk, and it is unlikely to affect your nursing baby. However, it’s important to have your thyroid hormone levels checked regularly to ensure you’re on the correct dosage. If you have any concerns, our telemedicine providers can help you manage your treatment while breastfeeding.
Estimated Cost of Levothyroxine
The cost of Levothyroxine can vary depending on the pharmacy and your location. With a GoodRx coupon, the estimated cost for a 30-day supply without insurance typically ranges from $4 to $15, depending on the dosage. Prices may fluctuate, so it’s a good idea to check with your pharmacy or use a coupon service like GoodRx to find the most affordable option for your thyroid medication.
Possible Alternatives to Levothyroxine
While Levothyroxine is the standard treatment for many thyroid conditions, there are alternative therapies and lifestyle changes that may be helpful. Always consult your healthcare provider before making any changes to your treatment plan. Our telemedicine providers are available to guide you through these options.
Hypothyroidism Treatment Alternatives
Some individuals may benefit from alternative thyroid hormone replacements, such as Liothyronine (Cytomel) or natural desiccated thyroid (Armour Thyroid). Dietary changes, like increasing iodine intake, may also be beneficial, but only under the supervision of a healthcare provider.
Hashimoto’s Thyroiditis
In addition to Levothyroxine, managing inflammation through dietary changes (such as adopting a gluten-free or anti-inflammatory diet) and supplements like selenium may be helpful. However, these options should always be discussed with your healthcare provider.
Thyroid Cancer
After thyroid surgery, Levothyroxine is often prescribed to suppress TSH levels. Other treatment options may include radioactive iodine therapy or additional thyroid hormone suppressants, depending on the type of thyroid cancer.
Goiter
Levothyroxine is frequently used to reduce the size of a goiter. However, in some cases, surgery or radioactive iodine treatment may be necessary. If the goiter is due to iodine deficiency, iodine supplementation may also be recommended.
Congenital Hypothyroidism
Levothyroxine is the standard treatment for congenital hypothyroidism. There are no known alternatives, but early diagnosis and treatment are crucial for ensuring normal development in affected infants.
Myxedema Coma
This is a life-threatening medical emergency that requires immediate treatment with intravenous Levothyroxine and corticosteroids. There are no alternatives for this condition, and prompt intervention is critical.
Pituitary Gland Disorders
If hypothyroidism is caused by a pituitary disorder, treating the underlying condition—such as through surgery or hormone replacement therapy—may be necessary in addition to taking Levothyroxine.
Thyroid Hormone Deficiency
Levothyroxine is the primary treatment for thyroid hormone deficiency. In rare cases, combination therapy with Liothyronine (T3) may be considered, but this should be carefully evaluated by your healthcare provider.
Iodine Deficiency
Increasing iodine intake through diet or supplements can help address iodine deficiency. However, if hypothyroidism has already developed, Levothyroxine may still be required to manage the condition.
Thyroiditis
Treatment for thyroiditis depends on the specific type. In some cases, anti-inflammatory medications or beta-blockers may be used alongside Levothyroxine to manage symptoms.
Recent Updates on Levothyroxine Research
Recent research on Levothyroxine has focused on optimizing dosing strategies to improve patient outcomes. A 2022 study suggested that taking Levothyroxine at bedtime, rather than in the morning, may enhance absorption and stabilize thyroid hormone levels in some patients. However, more research is needed before this becomes a standard recommendation.
Another area of ongoing research is the potential benefit of combination therapy with Levothyroxine and Liothyronine (T3) for patients who don’t feel fully well on Levothyroxine alone. While some studies show promise, this approach is not yet widely recommended due to concerns about safety and long-term effects.
As always, it’s important to discuss any new research or treatment options with your healthcare provider. If you’re interested in learning more about recent developments in thyroid treatment, our telemedicine providers are here to help you explore your options.
