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This is an information resource — not medical advice.

PillCodex provides general educational information about medications. This content is not a substitute for professional medical advice, diagnosis, or treatment. Never start, stop, or change a medication based on what you read here. Always speak to your doctor, pharmacist, or qualified healthcare provider with questions about your medications.

🚨 If you are experiencing a medical emergency or think you may have taken too much of a medication, call emergency services (911 in the US) or go to your nearest emergency room immediately.

Thyroid Hormone Replacement🔒 Prescription only

What Is Levothyroxine (Synthroid) Used For?

Brand names: Synthroid, Levoxyl, Tirosint

Levothyroxine is a synthetic thyroid hormone (T4) used to replace hormone that an underactive or removed thyroid gland cannot produce.

What is Levothyroxine used for?

  • Hypothyroidism (underactive thyroid)
  • Thyroid cancer (after removal)
  • Goiter (enlarged thyroid)
  • Thyroid nodules

How does Levothyroxine work?

The thyroid gland produces T4 hormone which regulates metabolism, energy, and heart rate. When underactive or removed, levothyroxine replaces this hormone restoring normal function.

Dosage information

💊Available forms
  • 25mcg tablets
  • 50mcg tablets
  • 75mcg tablets
  • 88mcg tablets
  • 100mcg tablets
  • +3 more
📏Typical dosage

Highly individualized. Average adult dose is 1.6 mcg/kg/day. Taken once daily on an empty stomach 30–60 minutes before breakfast.

⚠️ Dosage varies by individual. Always follow your doctor's or pharmacist's instructions — never self-dose based on general information.

Side effects

Common

  • Most side effects from too high a dose: hair loss (usually temporary)
  • Weight loss
  • Rapid heartbeat
  • Nervousness
  • Insomnia
  • Sweating

⚠️ Serious — contact your doctor

  • Chest pain or palpitations
  • Bone density loss with long-term overtreatment

Important warnings

Take on an empty stomach 30–60 minutes before breakfast
Many foods and medications interfere with absorption
Do not switch brands without consulting your doctor
Regular TSH blood tests needed

Drug interactions

These substances may interact with Levothyroxine. This is not a complete list — always tell your doctor and pharmacist ALL medications and supplements you take.

Calcium supplements (4 hours apart)Antacids (4 hours apart)Iron supplements (4 hours apart)Cholesterol medicationsSoy productsCoffee

Pregnancy & breastfeeding

🤰 Safe and essential during pregnancy — dose often needs adjustment

Always consult your doctor or obstetrician before taking any medication during pregnancy or while breastfeeding.

Frequently asked questions

What is levothyroxine used for?

Levothyroxine treats hypothyroidism (underactive thyroid) and is used after thyroid surgery or radioactive iodine treatment.

What foods should I avoid with levothyroxine?

Take on an empty stomach and wait 30–60 minutes before eating. Calcium-rich foods, soy, high-fiber foods, coffee, and grapefruit can reduce absorption.

Can I take levothyroxine with coffee?

Coffee significantly reduces absorption. Wait at least 30–60 minutes after taking levothyroxine before drinking coffee.

Does levothyroxine cause weight loss?

When treating hypothyroidism, some weight loss is expected as metabolism normalizes. It is not a weight-loss drug and is dangerous to take without a thyroid condition.

Why do I feel worse after starting levothyroxine?

Some people feel temporarily worse as the body adjusts. Side effects of too high a dose mean the dose may need adjusting. Regular TSH tests help.

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This is an information resource — not medical advice.

PillCodex provides general educational information about medications. This content is not a substitute for professional medical advice, diagnosis, or treatment. Never start, stop, or change a medication based on what you read here. Always speak to your doctor, pharmacist, or qualified healthcare provider with questions about your medications.

🚨 If you are experiencing a medical emergency or think you may have taken too much of a medication, call emergency services (911 in the US) or go to your nearest emergency room immediately.

Information on this page is sourced from general pharmaceutical references and is provided for educational purposes only. Drug information may change — always verify with your pharmacist or prescriber. PillCodex.com is not affiliated with any pharmaceutical company.