Levothyroxine is a synthetic thyroid hormone. Doctors prescribe it for people whose thyroid gland does not make enough hormone, a condition called hypothyroidism. Most people take it for life.
What Is Levothyroxine Used For?
- Hypothyroidism (underactive thyroid)
- Preventing goiter and thyroid enlargement
- Thyroid cancer, along with other treatment
How Does Levothyroxine Work?
Levothyroxine replaces the thyroid hormone your body lacks. This brings your energy, metabolism, and heart rate back to normal.
General Dosage Information
This is general information only. Your doctor sets the right dose for you, so follow your prescription and the label.
- Doctors often start full replacement at about 1.6 micrograms per kilogram of body weight a day, and start lower in older adults and people with heart disease.
- Take it once a day on an empty stomach, with water, 30 to 60 minutes before breakfast.
- Your doctor checks your TSH level about six to eight weeks after a dose change.
Side Effects of Levothyroxine
Common Side Effects
- Usually none when the dose is right
- Too much hormone can cause: fast heartbeat, shaking, sweating, weight loss, trouble sleeping, and anxiety
- Too little hormone can cause: tiredness, weight gain, cold intolerance, and constipation
Serious Side Effects
Call your doctor or get emergency help if you notice:
- Chest pain or a very fast or irregular heartbeat
- Severe shortness of breath
- Signs of an allergic reaction
Who Should Be Cautious?
- People with heart disease, who need a slow, careful start
- Older adults
- People with adrenal problems
- Pregnant women, who often need a higher dose and should talk to their doctor
Drug Interactions
Tell your doctor and pharmacist about every medicine and supplement you take. Examples of important interactions include:
- Calcium, iron, and antacids: take levothyroxine at least four hours apart.
- Acid reducers such as PPIs: they can lower absorption.
- Warfarin: levothyroxine can raise its effect.
- Biotin supplements: they can distort thyroid blood tests, so tell your doctor.
- Soy products, high-fiber foods, and coffee: they can lower absorption, so keep your routine steady.
Storage and Precautions
- Store it at room temperature, away from heat, light, and moisture.
- Keep it out of the reach of children.
Frequently Asked Questions
Can I take it with coffee?
Wait 30 to 60 minutes after taking it before coffee or breakfast.
Will it help me lose weight?
No. Do not take it for weight loss, because it is dangerous at high doses.
Can I switch brands?
Tell your doctor, and have your TSH checked after a change.
Disclaimer: This article is for information only. It is not medical advice. Please talk to your doctor about your own health.