Levothyroxine (Thyroid Medicine)

What is Levothyroxine?

Levothyroxine is a medicine that replaces thyroid hormone in the body. It helps when the thyroid gland does not make enough hormone. This condition is called hypothyroidism.

Thyroid hormone helps control:

• Growth
• Energy levels
• Body temperature
• Heart rate
• Brain development
• Metabolism (how the body uses energy)

This medicine helps your child’s body work normally and supports healthy growth and development.

Common Brand Names

Some common brand names include:

• Synthroid
• Levoxyl
• Unithroid
• Tirosint

How Should My Child Take This Medicine?

• Give the medicine exactly as prescribed.
• Levothyroxine works best when taken on an empty stomach.
• Give it with water, usually 30–60 minutes before breakfast.
• Try to give it at the same time every day.
• Do not stop the medicine unless your child’s provider tells you to.

For Babies or Young Children

If your child cannot swallow pills:

• Crush the tablet and mix it with a small amount of water.
• Give it right away with a spoon or dropper.
• Do not mix it with soy formula or large amounts of food.

What If I Miss a Dose?

• If you remember the same day, give the missed dose as soon as possible.
• If it is almost time for the next dose, skip the missed dose.
• Do not give two doses at the same time unless your provider tells you to.

If you are not sure what to do, contact your child’s healthcare provider.

Possible Side Effects

Most children do well on levothyroxine when the dose is correct.

Call your provider if your child has:

• Fast heartbeat
• Chest pain
• Trouble sleeping
• Nervousness or shaking
• Sweating more than usual
• Weight loss
• Headaches
• Diarrhea

These may mean the dose is too high.

Signs the dose may be too low:

• Tiredness
• Feeling cold often
• Dry skin
• Constipation
• Slow growth
• Trouble concentrating

Important Tips

• Your child will need regular blood tests to check thyroid levels.
• Different brands may work slightly differently. Check with your provider before changing brands.
• Some vitamins and medicines can affect levothyroxine.

Give levothyroxine at least 4 hours apart from:

• Iron supplements
• Calcium supplements
• Antacids

When to Call the Healthcare Provider

Call your child’s provider if:

• Your child misses several doses
• Your child has side effects
• Your child has trouble taking the medicine
• You notice major changes in energy, mood, growth, or weight

Seek emergency care for:

• Severe chest pain
• Trouble breathing
• Fainting

Storage

• Store at room temperature.
• Keep away from heat, light, and moisture.
• Keep out of reach of children.

Questions?

If you have questions about your child’s thyroid medicine, contact your pediatric endocrinology team.