Levothyroxine 100mcg
Generic For: Synthroid
Levothyroxine 100mcg (brand name Synthroid) is a synthetic thyroid hormone used to treat hypothyroidism and to help manage certain types of goiter and thyroid cancer. It replaces the hormone your thyroid gland does not make in sufficient amounts. After a licensed provider reviews your prescription, your order ships from a licensed U.S. pharmacy.
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90-day supply · $0.28/tablet
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Buy Levothyroxine 100mcg (Synthroid) Online
A thyroid hormone replacement for hypothyroidism, goiter, and thyroid cancer management
Levothyroxine 100mcg Quick Facts
| Drug class | Thyroid hormone replacement |
|---|---|
| Treats | Hypothyroidism, goiter, thyroid cancer (TSH suppression) |
| Form | Tablet |
| Typical dosing | Take 1 tablet by mouth daily in the morning. |
| Prescription required | Yes — prescription only |
What Is Levothyroxine 100mcg?
Levothyroxine is a man-made version of thyroxine (T4), the main hormone produced by the thyroid gland. It is prescribed when the thyroid does not make enough hormone on its own, a condition called hypothyroidism. Taken consistently, levothyroxine helps restore normal hormone levels, which supports energy, metabolism, and body temperature regulation. It is one of the most commonly prescribed medications in the United States and is available as the brand Synthroid and as a generic.
What Does Levothyroxine 100mcg Treat?
Hypothyroidism (underactive thyroid)
Hypothyroidism after thyroid surgery or radioactive iodine therapy
Congenital hypothyroidism
Pituitary (secondary) or hypothalamic (tertiary) hypothyroidism
Euthyroid goiter management
TSH suppression in well-differentiated thyroid cancer (adjunct)
Levothyroxine 100mcg Dosage
Adults with hypothyroidism: approximately 1.6 mcg/kg by mouth once daily.
Take on an empty stomach, 30–60 minutes before breakfast, with water.
Dose is individualized and adjusted based on TSH labs every 4–6 weeks until stable.
Your prescriber will determine the dose and duration that are right for you. Always follow the directions on your prescription label.
Levothyroxine 100mcg Side Effects
Common side effects
- Hair loss (usually temporary, early in treatment)
- Headache
- Nervousness or irritability
- Trouble sleeping
- Increased sweating
- Changes in appetite or weight
- Diarrhea
- Menstrual cycle changes
Serious side effects
Stop taking this medication and seek medical attention right away if you experience:
- Chest pain or rapid, irregular heartbeat
- Signs of allergic reaction (rash, swelling, difficulty breathing)
- Severe headache or tremor
- Excessive weight loss or heat intolerance (possible overtreatment)
- Seizures
- Bone fracture or signs of decreased bone density with long-term overtreatment
Warnings & Interactions
Boxed warning: not for weight loss; large doses may cause serious or life-threatening effects
Do not use with uncorrected adrenal insufficiency
Use caution with heart disease; may worsen angina or arrhythmias
Separate from calcium, iron, antacids, and cholestyramine by at least 4 hours
Many drugs (e.g., warfarin, insulin, digoxin) may need dose adjustments
Overtreatment can reduce bone mineral density, especially in postmenopausal women
Tell your provider if you are pregnant; dose requirements often increase during pregnancy
Tell your prescriber about all medications, supplements, and health conditions before starting levothyroxine 100mcg.
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