Levothyroxine 0.100mg(100mcg) Tab
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 products; Hormones
Pregnancy Category
Category A
FDA Approved
Jan 1965
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 products, 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 immediately after mixing, and do not store it for later 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 your medication.
If you take other medications, they may need to be taken at a different time than your current medication. Consult with your doctor or pharmacist to determine the best schedule.
Certain foods, such as soybean flour (found in infant formula), may affect how your medication works. 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 your medication 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 is 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 products, 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 immediately after mixing, and do not store it for later 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 your medication.
If you take other medications, they may need to be taken at a different time than your current medication. Consult with your doctor or pharmacist to determine the best schedule.
Certain foods, such as soybean flour (found in infant formula), may affect how your medication works. 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 your medication 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 is 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, preferably 30-60 minutes before breakfast, with a full glass of water.
- Avoid taking with calcium, iron, antacids, or fiber supplements within 4 hours of your dose.
- Inform your doctor about all other medications, supplements, and herbal products you are taking.
- Do not stop taking this medication without consulting your doctor, even if you feel better.
- Regular blood tests (TSH) are crucial to ensure the correct dose.
- Maintain a consistent diet; avoid sudden changes in fiber or soy intake.
- Store at room temperature, away from moisture and heat.
Available Forms & Alternatives
Available Strengths:
- Levothyroxine 0.100mg(100mcg) Tab
- Levothyroxine 0.075mg (75mcg) Tabs
- Levothyroxine 0.125mg (125mcg) Tab
- Levothyroxine 0.05mg (50mcg) Tab
- Levothyroxine 0.025mg (25mcg) Tab
- Levothyroxine 0.112mg (112mcg) Tabs
- Levothyroxine 0.137mg (137mcg) Tab
- Levothyroxine 0.175mg (175mcg) Tabs
- Levothyroxine 500mcg Inj, 1 Vial
- Levothyroxine Sod 100mcg Inj, 1vial
- Levothyroxine 200mcg Inj, 1 Vial
- Levothyroxine 0.088mg (88mcg) Tab
- Levothyroxine 0.100mg (100mcg) Tab
- Levothyroxine 0.150mg (150mcg) Tab
- Levothyroxine 0.2mg (200mcg) Tab
- Levothyroxine 0.3mg (300mcg) Tab
- Levothyroxine 0.013mg (13mcg) Caps
- Levothyroxine 0.025mg (25mcg) Caps
- Levothyroxine 0.05mg (50mcg) Caps
- Levothyroxine 0.075mg (75mcg) Caps
- Levothyroxine 0.088mg (88mcg) Caps
- Levothyroxine 0.100mg (100mcg) Caps
- Levothyroxine 0.112mg (112mcg) Caps
- Levothyroxine 0.125mg (125mcg) Caps
- Levothyroxine 0.137mg (137mcg) Caps
- Levothyroxine 0.150mg (150mcg) Caps
- Levothyroxine 0.175mg (175mcg) Caps
- Levothyroxine 0.2mg (200mcg) Caps
- Levothyroxine 0.125mg (125mcg) Tabs
- Levothyroxine 100mcg/5ml Inj, 5ml
- Levothyroxine 100mcg/ml Inj, 1ml
- Levothyroxine 500mg/5ml Inj, 5ml
- Levothyroxine 200mcg/5ml Inj, 5ml
Dosing & Administration
Adult Dosing
Standard Dose:
Initial dose typically 1.6 mcg/kg/day orally once daily for primary hypothyroidism. Dosage is highly individualized based on TSH levels.
Dose Range:
25 - 300 mg
Condition-Specific Dosing:
cardiacDisease:
Initial dose 12.5-25 mcg/day, titrate slowly.
elderly:
Initial dose 12.5-25 mcg/day, titrate slowly.
subclinicalHypothyroidism:
Initial dose 25-75 mcg/day, titrate 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, monitor TSH.
Moderate:
No specific adjustment needed, monitor TSH.
Severe:
No specific adjustment needed, monitor TSH.
Dialysis:
No specific adjustment needed, monitor TSH. Levothyroxine is highly protein-bound and not significantly removed by dialysis.
Hepatic Impairment:
Mild:
No specific adjustment needed, monitor TSH.
Moderate:
No specific adjustment needed, monitor TSH.
Severe:
No specific adjustment needed, monitor TSH. May require lower doses in severe liver disease due to altered protein binding and metabolism.
Pharmacology
Mechanism of Action
Levothyroxine (T4) is a synthetic form of the naturally occurring thyroid hormone, thyroxine. It is converted to its active metabolite, liothyronine (T3), in peripheral tissues. T3 then enters the cell nucleus and binds to thyroid hormone receptors, regulating gene expression and controlling numerous metabolic processes, including protein synthesis, carbohydrate metabolism, lipid metabolism, and cellular respiration. It is essential for normal growth, development, and metabolism.
Pharmacokinetics
Absorption:
Bioavailability:
40-80% (highly variable, affected by food and other drugs)
Tmax:
2-4 hours
FoodEffect:
Decreased absorption when taken with food, especially fiber, calcium, iron, and certain foods (e.g., soybean flour, cottonseed meal, walnuts, grapefruit juice). 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), transthyretin (TTR), and albumin)
CnssPenetration:
Limited (T3 crosses BBB more readily than T4)
Elimination:
HalfLife:
Approximately 7 days (range 6-10 days); shorter in hyperthyroidism, longer in hypothyroidism.
Clearance:
Approximately 0.05 L/hr/kg
ExcretionRoute:
Primarily renal (approximately 80% of metabolites), some fecal (approximately 20% of unchanged drug and metabolites).
Unchanged:
Approximately 20% (fecal excretion)
Pharmacodynamics
OnsetOfAction:
Gradual, clinical effects may not be apparent for several days to weeks.
PeakEffect:
Peak therapeutic effect typically seen 3-4 weeks after initiation or dose change.
DurationOfAction:
Due to long half-life, effects persist for several days after discontinuation.
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
Serious Side Effects: Seek Medical Help Immediately
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention right away:
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 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. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or do not go away, contact your doctor:
* Hair loss (usually temporary and resolves on its own within the first few months of treatment)
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention right away:
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 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. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or do not go away, contact your doctor:
* Hair loss (usually temporary and resolves on its own within the first few months of treatment)
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, contact 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:
- Symptoms of too much thyroid hormone (hyperthyroidism): rapid heart rate, palpitations, chest pain, excessive sweating, nervousness, tremor, unexplained weight loss, diarrhea, insomnia.
- Symptoms of too little thyroid hormone (hypothyroidism): extreme fatigue, severe constipation, unexplained weight gain, feeling very cold, depression, hair loss.
- Allergic reaction: rash, itching, swelling (especially of face/tongue/throat), severe dizziness, trouble breathing.
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 symptoms you experienced.
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 and medications with your doctor.
To ensure your safety, provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter medications you are taking
Natural products and vitamins you are using
* Any health problems you have
Before making any changes to your medication regimen, including starting, stopping, or adjusting the dose of any drug, consult with your doctor to confirm it is safe to do so.
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 symptoms you experienced.
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 and medications with your doctor.
To ensure your safety, provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter medications you are taking
Natural products and vitamins you are using
* Any health problems you have
Before making any changes to your medication regimen, including starting, stopping, or adjusting the dose of any drug, consult with your doctor to confirm it is safe to do so.
Precautions & Cautions
Important Information for All Patients Taking This Medication
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. To ensure uninterrupted treatment, do not run out of this medication, as it may take several weeks to experience its full effects.
Special Considerations
If you have diabetes (high blood sugar), consult your doctor, as this medication may affect 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 take biotin or products 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 osteoporosis (weak bones), particularly after menopause. Discuss your risk factors with your doctor, who can help determine if you are at higher risk of developing osteoporosis.
This medication may also affect fertility, potentially leading to difficulty getting pregnant or fathering a child. If you plan to conceive, consult your doctor before starting treatment.
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 to discuss the benefits and risks of this medication to you and your baby.
Pediatric Patients
If your child is taking this medication and experiences weight changes, consult your doctor, as the dosage may need to be adjusted. Never give your child more 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 consult your doctor to monitor your child's growth and development.
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. To ensure uninterrupted treatment, do not run out of this medication, as it may take several weeks to experience its full effects.
Special Considerations
If you have diabetes (high blood sugar), consult your doctor, as this medication may affect 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 take biotin or products 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 osteoporosis (weak bones), particularly after menopause. Discuss your risk factors with your doctor, who can help determine if you are at higher risk of developing osteoporosis.
This medication may also affect fertility, potentially leading to difficulty getting pregnant or fathering a child. If you plan to conceive, consult your doctor before starting treatment.
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 to discuss the benefits and risks of this medication to you and your baby.
Pediatric Patients
If your child is taking this medication and experiences weight changes, consult your doctor, as the dosage may need to be adjusted. Never give your child more 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 consult your doctor to monitor your child's growth and development.
Overdose Information
Overdose Symptoms:
- Signs of hyperthyroidism: palpitations, tachycardia, arrhythmias, chest pain, tremor, nervousness, insomnia, excessive sweating, heat intolerance, weight loss, diarrhea, fever, seizures, coma.
What to Do:
Seek immediate medical attention or call a poison control center (1-800-222-1222). Treatment is supportive and symptomatic, often involving beta-blockers for cardiac symptoms and corticosteroids for severe cases. Gastric lavage or activated charcoal may be considered if ingestion is recent.
Drug Interactions
Major Interactions
- Amiodarone (may cause hypo- or hyperthyroidism)
- Antacids (aluminum, magnesium, calcium) - decrease absorption
- Bile acid sequestrants (cholestyramine, colestipol, colesevelam) - decrease absorption
- Calcium carbonate/supplements - decrease absorption
- Cation exchange resins (sodium polystyrene sulfonate) - decrease absorption
- Iron supplements - decrease absorption
- Orlistat - decrease absorption
- Proton pump inhibitors (PPIs) - decrease absorption (due to increased gastric pH)
- Sucralfate - decrease absorption
- Soybean flour (in infant formula) - decrease absorption
- Tyrosine kinase inhibitors (e.g., imatinib, sunitinib) - may alter thyroid function
- Warfarin (increased anticoagulant effect)
Moderate Interactions
- Anticonvulsants (carbamazepine, phenytoin, phenobarbital) - increase metabolism of levothyroxine
- Antidepressants (tricyclics, SSRIs) - may increase cardiac effects of levothyroxine
- Beta-blockers - may decrease conversion of T4 to T3
- Corticosteroids - may decrease TSH and T4 levels
- Digoxin - levothyroxine may decrease digoxin levels
- Estrogens (oral) - increase TBG, requiring higher levothyroxine dose
- Furosemide (>80 mg IV) - may displace T4 from protein binding
- Iodine-containing products (e.g., contrast media) - may alter thyroid function
- Metformin - may decrease TSH levels
- Propylthiouracil (PTU) - inhibits T4 to T3 conversion
- Rifampin - increases metabolism of levothyroxine
- Ritonavir - may alter thyroid function
- Sertraline - may decrease levothyroxine absorption
- Statins (e.g., lovastatin, simvastatin) - may alter thyroid function tests
Minor Interactions
- Dietary fiber - may decrease absorption
- Grapefruit juice - may decrease absorption
Monitoring
Baseline Monitoring
Thyroid-stimulating hormone (TSH)
Rationale: Primary diagnostic marker for hypothyroidism and to guide initial dosing.
Timing: Before initiation of therapy.
Free Thyroxine (Free T4)
Rationale: To assess baseline thyroid hormone levels, especially if TSH is abnormal or in central hypothyroidism.
Timing: Before initiation of therapy.
Clinical symptoms of hypothyroidism
Rationale: To establish baseline symptom severity and track improvement.
Timing: Before initiation of therapy.
Cardiac status (ECG, history of heart disease)
Rationale: To assess risk of adverse cardiac events, especially in elderly or those with pre-existing heart conditions.
Timing: Before initiation, particularly in older adults or those with cardiac risk factors.
Routine Monitoring
Thyroid-stimulating hormone (TSH)
Frequency: Every 4-8 weeks after initiation or dose change, then every 6-12 months once stable.
Target: 0.4-4.0 mIU/L (individualized target may be lower for some patients, e.g., 0.5-2.5 mIU/L).
Action Threshold: Adjust dose if TSH is outside target range; higher TSH indicates need for dose increase, lower TSH indicates need for dose decrease.
Free Thyroxine (Free T4)
Frequency: May be monitored if TSH is suppressed or in central hypothyroidism, or if clinical response is inconsistent with TSH.
Target: 0.8-1.8 ng/dL (or laboratory-specific reference range).
Action Threshold: Adjust dose if Free T4 is outside target range, especially if TSH is not reliable.
Clinical symptoms (e.g., fatigue, weight, mood, constipation, cold intolerance)
Frequency: At each visit, especially during dose titration.
Target: Resolution or significant improvement of hypothyroid symptoms.
Action Threshold: Persistent or worsening symptoms despite normal TSH may indicate need for further investigation or dose adjustment.
Bone mineral density (BMD)
Frequency: Periodically, especially in postmenopausal women or those on long-term suppressive therapy (e.g., for thyroid cancer).
Target: Maintain normal BMD.
Action Threshold: Consider dose reduction if TSH is consistently suppressed below target in patients without thyroid cancer, to minimize risk of osteoporosis.
Symptom Monitoring
- Symptoms of hypothyroidism (fatigue, weight gain, constipation, cold intolerance, dry skin, hair loss, depression, bradycardia)
- Symptoms of hyperthyroidism (palpitations, tachycardia, nervousness, tremor, weight loss, heat intolerance, diarrhea, insomnia, anxiety)
- Signs of cardiac effects (chest pain, shortness of breath, irregular heartbeat)
Special Patient Groups
Pregnancy
Levothyroxine is Category A and is essential for normal fetal development. Hypothyroidism during pregnancy can lead to adverse maternal and fetal outcomes. Dose requirements typically increase during pregnancy (by 25-50% or more) due to increased TBG and fetal thyroid hormone needs. TSH should be monitored every 4-6 weeks.
Trimester-Specific Risks:
First Trimester:
Untreated maternal hypothyroidism in the first trimester is associated with increased risk of miscarriage, preterm birth, preeclampsia, and impaired neurocognitive development in the offspring.
Second Trimester:
Continued need for increased dose; fetal thyroid gland begins to function, but maternal thyroid hormone remains crucial.
Third Trimester:
Dose requirements remain elevated. Close monitoring of TSH is essential.
Lactation
Levothyroxine is considered safe during breastfeeding (L1). Only small amounts are excreted into breast milk, which are not sufficient to cause adverse effects in the infant or affect infant thyroid function. It is compatible with breastfeeding.
Infant Risk:
Minimal to none.
Pediatric Use
Dosing is weight-based and higher per kg than in adults, especially in neonates and infants, due to rapid growth and higher metabolic rates. Close monitoring of TSH and Free T4 is crucial to ensure normal growth and neurocognitive development. Tablets can be crushed and mixed with a small amount of water or breast milk/formula and given by spoon or dropper; do not mix with soybean formula or iron-fortified formula.
Geriatric Use
Lower starting doses (12.5-25 mcg/day) are recommended, especially in patients with pre-existing cardiac disease, due to increased sensitivity to thyroid hormones and higher risk of cardiac adverse events. Dose titration should be slower and TSH monitored closely.
Clinical Information
Clinical Pearls
- Always take levothyroxine on an empty stomach, 30-60 minutes before breakfast, with water, to maximize absorption.
- Separate administration of levothyroxine from calcium, iron, antacids, and other interacting medications by at least 4 hours.
- Consistency is key: take at the same time each day and use the same brand/generic product if possible, as bioavailability can vary between formulations.
- Patients may not feel the full effect of a dose change for several weeks due to the long half-life.
- TSH is the primary lab test for monitoring, but Free T4 may be useful in specific situations (e.g., central hypothyroidism, TSH suppression).
- Educate patients on symptoms of both hypo- and hyperthyroidism to ensure timely reporting of adverse effects or inadequate dosing.
- In pregnant patients, levothyroxine dose requirements typically increase significantly; monitor TSH every 4-6 weeks.
Alternative Therapies
- Liothyronine (T3) - used in specific cases, e.g., myxedema coma, or short-term before radioactive iodine scan, but not for routine chronic replacement due to shorter half-life and fluctuating levels.
Cost & Coverage
Average Cost:
$10 - $50 per 30 tablets (for 100mcg)
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 is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it is a good idea to check with your pharmacist for more information. If you have any questions or concerns about this medication, consult with 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 reporting the incident, be prepared to provide details about the medication taken, the amount, and the time it occurred.