Euthyrox 0.125mg (125mcg) Tablets
WARNING: Do not use this drug for weight loss. Severe and sometimes deadly side effects may happen with this drug if it is taken in large doses or with other drugs for weight loss. If you have questions, talk with the doctor. @ COMMON USES: It is used to add thyroid hormone to the body.It is used to manage thyroid cancer.It may be given to you for other reasons. Talk with the doctor.
Drug Class
Thyroid hormone replacement
Pharmacologic Class
Thyroid hormones
Pregnancy Category
Category A
FDA Approved
Jul 1949
DEA Schedule
Not Controlled
Overview
What is this medicine?
Levothyroxine is a medicine that replaces a hormone normally made by your thyroid gland. It's used to treat an underactive thyroid (hypothyroidism). Taking this medicine helps your body work properly, improving symptoms like tiredness, weight gain, and feeling cold.
How to Use This Medicine
Taking Your Medication Correctly
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely.
Take your medication on an empty stomach, at least 30 to 60 minutes before breakfast.
Some brands of this medication may cause choking, gagging, or trouble swallowing. If you have one of these brands, be sure to take it with a full glass of water. Check with your pharmacist if you're unsure.
If you need to, you can crush your tablet and mix it with 1 or 2 teaspoons (5 or 10 mL) of water. Take the dose right away after mixing, and do not store it for future use.
Important Interactions to Consider
Do not take iron products, antacids containing aluminum or magnesium, or calcium carbonate within 4 hours before or 4 hours after taking this medication.
If you take other medications, they may need to be taken at a different time than this medication. Check with your doctor or pharmacist for guidance on the best schedule.
Certain foods, such as soybean flour (found in infant formula), may affect how this medication works in your body. Discuss this with your doctor.
If you regularly drink grapefruit juice or eat grapefruit, talk to your doctor about potential interactions.
Using the Correct Form of Your Medication
There are different brands and forms of this medication. Do not switch between them without consulting your doctor.
Continue taking your medication as directed by your doctor or healthcare provider, even if you feel well.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, away from the bathroom.
Protect it from heat and light.
If your medication comes in a blister pack, do not remove it until you are ready to take it. Do not store the removed medication for future use.
What to Do If You Miss a Dose
Take a missed dose as soon as you remember.
If it's close to the time for your next dose, skip the missed dose and return to your regular schedule.
* Do not take two doses at the same time or take extra doses.
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely.
Take your medication on an empty stomach, at least 30 to 60 minutes before breakfast.
Some brands of this medication may cause choking, gagging, or trouble swallowing. If you have one of these brands, be sure to take it with a full glass of water. Check with your pharmacist if you're unsure.
If you need to, you can crush your tablet and mix it with 1 or 2 teaspoons (5 or 10 mL) of water. Take the dose right away after mixing, and do not store it for future use.
Important Interactions to Consider
Do not take iron products, antacids containing aluminum or magnesium, or calcium carbonate within 4 hours before or 4 hours after taking this medication.
If you take other medications, they may need to be taken at a different time than this medication. Check with your doctor or pharmacist for guidance on the best schedule.
Certain foods, such as soybean flour (found in infant formula), may affect how this medication works in your body. Discuss this with your doctor.
If you regularly drink grapefruit juice or eat grapefruit, talk to your doctor about potential interactions.
Using the Correct Form of Your Medication
There are different brands and forms of this medication. Do not switch between them without consulting your doctor.
Continue taking your medication as directed by your doctor or healthcare provider, even if you feel well.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, away from the bathroom.
Protect it from heat and light.
If your medication comes in a blister pack, do not remove it until you are ready to take it. Do not store the removed medication for future use.
What to Do If You Miss a Dose
Take a missed dose as soon as you remember.
If it's close to the time for your next dose, skip the missed dose and return to your regular schedule.
* Do not take two doses at the same time or take extra doses.
Lifestyle & Tips
- Take on an empty stomach, at least 30-60 minutes before breakfast, with a full glass of water.
- Avoid taking with other medications, especially iron, calcium, antacids, or fiber supplements, for at least 4 hours.
- Take at the same time each day for consistency.
- Do not stop taking this medication without consulting your doctor, even if you feel better.
- Inform your doctor about all other medications, supplements, and herbal products you are taking.
- Maintain a consistent diet, especially regarding soy products, as they can affect absorption.
Available Forms & Alternatives
Available Strengths:
- Euthyrox 100mcg Tablets
- Euthyrox 0.125mg (125mcg) Tablets
- Euthyrox 88mcg Tablets
- Euthyrox 0.05mg (50mcg) Tablets
- Euthyrox 0.075mg (75mcg) Tablets
- Euthyrox 0.137mg (137mcg) Tab
- Euthyrox 0.175mg (175mcg) Tabs
- Euthyrox 0.150mg (150mcg) Tab
- Euthyrox 0.025mg (25mcg) Tab
- Euthyrox 0.112mg (112mcg) Tablets
- Euthyrox 0.2mg (200mcg) Tab
- Euthyrox 0.075mg (75mcg) Tablets
- Euthyrox 0.088mg (88mcg) Tablets
- Euthyrox 0.100mg (100mcg) Tablets
Dosing & Administration
Adult Dosing
Standard Dose:
Initial dose typically 1.6 mcg/kg/day orally once daily for primary hypothyroidism. Adjust by 12.5-25 mcg increments every 4-6 weeks based on TSH levels.
Dose Range:
25 - 300 mg
Condition-Specific Dosing:
elderly:
Initial dose 12.5-25 mcg/day, or 0.5 mcg/kg/day. Adjust slowly.
cardiacDisease:
Initial dose 12.5-25 mcg/day. Adjust slowly with caution.
subclinicalHypothyroidism:
Typically 25-75 mcg/day, individualized based on TSH.
Pediatric Dosing
Neonatal:
10-15 mcg/kg/day orally once daily (for congenital hypothyroidism).
Infant:
6-8 mcg/kg/day orally once daily (for 6-12 months).
Child:
4-6 mcg/kg/day orally once daily (for 1-5 years); 3-5 mcg/kg/day (for 6-12 years).
Adolescent:
2-3 mcg/kg/day orally once daily (for >12 years or during puberty, until adult dose is reached).
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment needed.
Moderate:
No specific adjustment needed.
Severe:
No specific adjustment needed.
Dialysis:
No specific adjustment needed. Monitor TSH.
Hepatic Impairment:
Mild:
No specific adjustment needed.
Moderate:
No specific adjustment needed.
Severe:
No specific adjustment needed.
Pharmacology
Mechanism of Action
Levothyroxine (T4) is a synthetic form of the natural thyroid hormone, thyroxine. It is converted to its active metabolite, liothyronine (T3), in peripheral tissues. T3 and T4 exert their metabolic effects through control of DNA transcription and protein synthesis. Thyroid hormones are involved in normal metabolism, growth, and development, and are essential for maintaining metabolic rate, cardiac function, and nervous system development.
Pharmacokinetics
Absorption:
Bioavailability:
48-79% (highly variable, affected by food and other drugs)
Tmax:
2-4 hours
FoodEffect:
Decreased absorption when taken with food, certain medications (e.g., iron, calcium, antacids, fiber supplements, proton pump inhibitors). Should be taken on an empty stomach, 30-60 minutes before breakfast.
Distribution:
Vd:
10-13 L
ProteinBinding:
>99% (primarily to thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin)
CnssPenetration:
Limited (T3 crosses BBB more readily than T4)
Elimination:
HalfLife:
6-7 days (euthyroid); 9-10 days (hypothyroid); 3-4 days (hyperthyroid)
Clearance:
Approximately 0.05 L/hour
ExcretionRoute:
Primarily renal (conjugated metabolites), some fecal (unabsorbed drug and biliary excretion)
Unchanged:
<1% (renal)
Pharmacodynamics
OnsetOfAction:
Gradual, over several days to weeks
PeakEffect:
Clinical effects typically seen within 3-4 weeks, full therapeutic effect may take 4-6 weeks due to long half-life and need for TSH stabilization.
DurationOfAction:
Effects persist for several days after discontinuation due to long half-life.
Safety & Warnings
BLACK BOX WARNING
Thyroid hormones, including Levothyroxine, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects.
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of high blood pressure, including:
+ Severe headache or dizziness
+ Passing out
+ Changes in eyesight
Chest pain or pressure
Fast or abnormal heartbeat
Shortness of breath
Sudden weight gain or swelling in the arms or legs
Headache
Feeling tired or weak
Changes in appetite
Unintentional weight changes
Diarrhea, stomach cramps, or vomiting
Mood changes, such as feeling irritable, nervous, excitable, or anxious
Shakiness
Trouble sleeping
Sensitivity to heat
Excessive sweating
Fever
Muscle cramps
Muscle weakness
Flushing
Bone pain
Changes in menstrual periods (in women)
In children: hip or knee pain, or a limp
In infants: changes in the shape of the head and face
Other Possible Side Effects
Like all medications, this drug can cause side effects. Many people may not experience any side effects or may only have mild ones. If you notice any of the following side effects or any other unusual symptoms, contact your doctor for advice:
Hair loss (usually temporary and resolves on its own)
Other side effects not listed here
If you have questions or concerns about side effects, talk to your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of high blood pressure, including:
+ Severe headache or dizziness
+ Passing out
+ Changes in eyesight
Chest pain or pressure
Fast or abnormal heartbeat
Shortness of breath
Sudden weight gain or swelling in the arms or legs
Headache
Feeling tired or weak
Changes in appetite
Unintentional weight changes
Diarrhea, stomach cramps, or vomiting
Mood changes, such as feeling irritable, nervous, excitable, or anxious
Shakiness
Trouble sleeping
Sensitivity to heat
Excessive sweating
Fever
Muscle cramps
Muscle weakness
Flushing
Bone pain
Changes in menstrual periods (in women)
In children: hip or knee pain, or a limp
In infants: changes in the shape of the head and face
Other Possible Side Effects
Like all medications, this drug can cause side effects. Many people may not experience any side effects or may only have mild ones. If you notice any of the following side effects or any other unusual symptoms, contact your doctor for advice:
Hair loss (usually temporary and resolves on its own)
Other side effects not listed here
If you have questions or concerns about side effects, talk to your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Signs of over-replacement (hyperthyroidism): rapid heart rate, palpitations, chest pain, excessive sweating, heat intolerance, nervousness, tremor, unexplained weight loss, diarrhea, insomnia.
- Signs of under-replacement (persistent hypothyroidism): extreme fatigue, severe constipation, unexplained weight gain, feeling very cold, depression, dry skin, hair loss.
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
Certain health conditions, including:
+ An overactive thyroid gland
+ A weak adrenal gland
+ Difficulty swallowing
This list is not exhaustive, and it is crucial to discuss all your health problems with your doctor.
Additionally, provide your doctor and pharmacist with a comprehensive list of all the medications you are taking, including:
Prescription medications
Over-the-counter (OTC) medications
Natural products
* Vitamins
It is vital to verify that it is safe to take this medication with all your other medications and health conditions. Never start, stop, or change the dose of any medication without first consulting your doctor.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
Certain health conditions, including:
+ An overactive thyroid gland
+ A weak adrenal gland
+ Difficulty swallowing
This list is not exhaustive, and it is crucial to discuss all your health problems with your doctor.
Additionally, provide your doctor and pharmacist with a comprehensive list of all the medications you are taking, including:
Prescription medications
Over-the-counter (OTC) medications
Natural products
* Vitamins
It is vital to verify that it is safe to take this medication with all your other medications and health conditions. Never start, stop, or change the dose of any medication without first consulting your doctor.
Precautions & Cautions
Important Information for All Patients Taking This Medication
It is crucial that you inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. To ensure uninterrupted treatment, do not allow your supply of this medication to run out. You may not experience the full effects of this medication for several weeks.
Special Considerations
If you have diabetes (high blood sugar), consult with your doctor, as this medication may affect your blood sugar control. Your doctor may need to adjust your diabetes medications. Be sure to monitor your blood sugar levels as directed by your doctor and undergo regular blood tests as recommended.
If you are taking biotin or a product containing biotin, stop taking it at least 2 days before having your thyroid levels checked to ensure accurate test results.
Potential Risks and Side Effects
High doses of this medication may increase the risk of developing weak bones (osteoporosis), particularly after menopause. Discuss your risk factors with your doctor, who can help determine if you are at higher risk or answer any questions you may have.
This medication may also affect fertility, potentially making it difficult to become pregnant or father a child. If you plan to conceive, consult with your doctor before starting this medication.
Age-Related Considerations
If you are 65 or older, use this medication with caution, as you may be more susceptible to side effects.
Pregnancy and Breastfeeding
If you are pregnant, plan to become pregnant, or are breastfeeding, inform your doctor, who will discuss the benefits and risks of this medication to you and your baby.
Pediatric Patients
If you are giving this medication to a child and their weight changes, consult with your doctor, as the dosage may need to be adjusted. Never give your child more of this medication than prescribed, as this can increase the risk of severe side effects.
In some cases, this medication may affect growth in children and teenagers. Regular growth checks may be necessary, so be sure to discuss this with your doctor.
It is crucial that you inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. To ensure uninterrupted treatment, do not allow your supply of this medication to run out. You may not experience the full effects of this medication for several weeks.
Special Considerations
If you have diabetes (high blood sugar), consult with your doctor, as this medication may affect your blood sugar control. Your doctor may need to adjust your diabetes medications. Be sure to monitor your blood sugar levels as directed by your doctor and undergo regular blood tests as recommended.
If you are taking biotin or a product containing biotin, stop taking it at least 2 days before having your thyroid levels checked to ensure accurate test results.
Potential Risks and Side Effects
High doses of this medication may increase the risk of developing weak bones (osteoporosis), particularly after menopause. Discuss your risk factors with your doctor, who can help determine if you are at higher risk or answer any questions you may have.
This medication may also affect fertility, potentially making it difficult to become pregnant or father a child. If you plan to conceive, consult with your doctor before starting this medication.
Age-Related Considerations
If you are 65 or older, use this medication with caution, as you may be more susceptible to side effects.
Pregnancy and Breastfeeding
If you are pregnant, plan to become pregnant, or are breastfeeding, inform your doctor, who will discuss the benefits and risks of this medication to you and your baby.
Pediatric Patients
If you are giving this medication to a child and their weight changes, consult with your doctor, as the dosage may need to be adjusted. Never give your child more of this medication than prescribed, as this can increase the risk of severe side effects.
In some cases, this medication may affect growth in children and teenagers. Regular growth checks may be necessary, so be sure to discuss this with your doctor.
Overdose Information
Overdose Symptoms:
- Palpitations
- Tachycardia
- Arrhythmias
- Chest pain
- Tremor
- Nervousness
- Insomnia
- Diaphoresis
- Heat intolerance
- Weight loss
- Diarrhea
- Vomiting
- Fever
- Seizures (rare)
- Heart failure (rare)
What to Do:
Seek immediate medical attention. Call 911 or Poison Control at 1-800-222-1222. Management is supportive and symptomatic, often involving beta-blockers for cardiac symptoms and measures to reduce absorption if recent ingestion.
Drug Interactions
Major Interactions
- Amiodarone (can cause hypo- or hyperthyroidism)
- Antacids (aluminum, magnesium, calcium) - decrease absorption
- Bile acid sequestrants (cholestyramine, colestipol) - decrease absorption
- Cation exchange resins (sevelamer, patiromer) - decrease absorption
- Iron supplements - decrease absorption
- Calcium supplements - decrease absorption
- Proton pump inhibitors (PPIs) - decrease absorption (due to increased gastric pH)
- Sucralfate - decrease absorption
- Orlistat - decrease absorption
- Soy products - decrease absorption
- Phenytoin, Carbamazepine, Rifampin, Phenobarbital (CYP inducers) - increase levothyroxine metabolism, requiring higher doses
- Warfarin - enhanced anticoagulant effect (monitor INR)
- Insulin/Oral Hypoglycemics - increased requirements (monitor glucose)
- Digoxin - decreased digoxin levels (monitor digoxin levels)
- SSRIs (sertraline) - may increase levothyroxine requirements
- Estrogens (oral) - increase TBG, increasing levothyroxine requirements
- Androgens - decrease TBG, decreasing levothyroxine requirements
Moderate Interactions
- Beta-blockers - may decrease conversion of T4 to T3
- Corticosteroids - may decrease conversion of T4 to T3
- Iodine-containing products - may affect thyroid function
- Dietary fiber - may decrease absorption
Minor Interactions
- Coffee - may decrease absorption (take separately)
Monitoring
Baseline Monitoring
Thyroid Stimulating Hormone (TSH)
Rationale: Primary diagnostic test for hypothyroidism and to guide initial dosing.
Timing: Prior to initiation of therapy.
Free Thyroxine (Free T4)
Rationale: To assess baseline thyroid hormone levels.
Timing: Prior to initiation of therapy.
Cardiac status (ECG, history of CAD)
Rationale: To assess for underlying cardiac disease, as thyroid hormone replacement can exacerbate cardiac symptoms.
Timing: Prior to initiation, especially in elderly or those with cardiac risk factors.
Routine Monitoring
Thyroid Stimulating Hormone (TSH)
Frequency: Every 4-6 weeks until stable, then every 6-12 months once stable.
Target: 0.4-4.0 mIU/L (for primary hypothyroidism, target often 0.5-2.5 mIU/L); individualized for TSH suppression.
Action Threshold: Adjust dose if TSH is outside target range.
Clinical symptoms (fatigue, weight, mood, cold intolerance)
Frequency: At each visit.
Target: Resolution or improvement of hypothyroid symptoms.
Action Threshold: Persistent symptoms may indicate need for dose adjustment or alternative diagnosis.
Heart rate, blood pressure
Frequency: At each visit.
Target: Normal limits.
Action Threshold: Tachycardia, palpitations, or hypertension may indicate over-replacement.
Symptom Monitoring
- Fatigue
- Weight gain
- Cold intolerance
- Constipation
- Dry skin
- Hair loss
- Bradycardia
- Depression
- Muscle aches
- Memory impairment
- Palpitations (sign of over-replacement)
- Tremor (sign of over-replacement)
- Anxiety (sign of over-replacement)
- Weight loss (sign of over-replacement)
- Heat intolerance (sign of over-replacement)
- Diarrhea (sign of over-replacement)
Special Patient Groups
Pregnancy
Levothyroxine is essential during pregnancy for normal fetal development. Maternal hypothyroidism during pregnancy can lead to adverse fetal and maternal outcomes. Dosage requirements often increase during pregnancy (by 25-50% or more). TSH should be monitored frequently (e.g., every 4 weeks) and dose adjusted to maintain TSH in the trimester-specific target range.
Trimester-Specific Risks:
First Trimester:
Untreated maternal hypothyroidism in the first trimester is associated with increased risk of miscarriage, preterm birth, and impaired neurocognitive development in the offspring.
Second Trimester:
Continued need for adequate thyroid hormone for fetal brain development.
Third Trimester:
Continued need for adequate thyroid hormone for fetal growth and development.
Lactation
Levothyroxine is considered safe during breastfeeding. Minimal amounts are excreted into breast milk, and it does not adversely affect the infant. It is crucial for the mother's health and milk production.
Infant Risk:
L1 (Safest) - No known adverse effects on the breastfed infant.
Pediatric Use
Dosing is weight-based and higher per kg in younger children due to higher metabolic rates and rapid growth. Close monitoring of TSH and clinical status is crucial for proper growth and neurocognitive development. Tablets can be crushed and mixed with a small amount of water or breast milk/formula for infants and young children; administer immediately.
Geriatric Use
Lower initial doses (e.g., 12.5-25 mcg/day) are recommended due to increased sensitivity to thyroid hormones and a higher prevalence of underlying cardiac disease. Dose adjustments should be made slowly and cautiously, with careful monitoring for cardiac symptoms.
Clinical Information
Clinical Pearls
- Always take levothyroxine on an empty stomach, 30-60 minutes before breakfast, with water, and separate from other medications (especially calcium, iron, antacids) by at least 4 hours.
- Consistency is key: take at the same time every day.
- Generic levothyroxine products are generally considered bioequivalent, but some patients and clinicians prefer to stick with the same brand or generic manufacturer once stable due to narrow therapeutic index and potential for slight variations in absorption.
- TSH is the primary lab test for monitoring, but Free T4 may also be useful, especially in central hypothyroidism or when TSH is suppressed.
- Symptoms of over-replacement (hyperthyroidism) can mimic anxiety or cardiac issues; always consider dose reduction if these occur.
- Patients with new onset angina or worsening cardiac symptoms after starting levothyroxine should have their dose reduced and cardiac status re-evaluated.
- Patients should be advised that it takes several weeks for the full therapeutic effect to be seen and for TSH levels to stabilize.
Alternative Therapies
- Liothyronine (T3) - used in specific cases, e.g., myxedema coma, or short-term TSH suppression prior to radioactive iodine scan. Has a shorter half-life and more pronounced peak effects.
Cost & Coverage
Average Cost:
$10 - $50 per 30 tablets (for generic 125mcg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 (Generic) or Tier 2 (Brand)
General Drug Facts
If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.