People can treat hypothyroidism by supplementing low thyroid hormone levels with levothyroxine or Armour Thyroid. However, only levothyroxine has Food and Drug Administration (FDA) approval.

Levothyroxine and natural desiccated thyroid (Armour Thyroid) are the two thyroid hormones available in the United States to replace thyroxine. People will need to take thyroid medication for life, and working out the ideal dosage with a clinician requires ongoing monitoring.

Hypothyroidism causes the thyroid gland to produce too little of a hormone called thyroxine. This can affect how the body processes energy and contributes to symptoms such as weight gain, low mood, and fatigue. However, daily hormone tablets can help to replace these hormones and reduce hypothyroidism’s effects on daily life.

This article explains the two options for hypothyroidism medications and their potential side effects.

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Levothyroxine is a lab-made version of the hormone that a typical-functioning thyroid would produce. Healthcare professionals usually prescribe it as an oral pill.

However, people with digestive issues can also purchase this in liquid form or as a soft gel capsule to improve the chance of successful gut absorption.

A healthcare professional might recommend taking levothyroxine in the morning 30 minutes to 1 hour before breakfast. Until they find a dose that successfully restores thyroxine levels and improves symptoms, a person will typically have a blood test every 6 to 8 weeks to check the medication’s effects and determine the right dose.

After this, a person may have another test in 6 months and yearly testing thereafter. It is important to keep the same dose and continue to take the medications as per the healthcare professional’s instructions.

Reducing or missing doses can mean that symptoms return, and taking too much of the medication can lead to complications such as osteoporosis or atrial fibrillation.

Learn more about levothyroxine.

A note on FDA approval

Levothyroxine is the only medication that currently has FDA approval for the treatment of hypothyroidism.

A healthcare professional can prescribe Armour Thyroid, also known as desiccated thyroid extract (DTE), if levothyroxine is not effective or if a person has issues with its effects. However, this is not FDA-approved and may have further and more serious side effects.

A person should speak with a healthcare professional about all potential side effects and complications.

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Armour Thyroid is a natural desiccated thyroid (NDT) medication containing an active ingredient called DTE. Manufacturers extract DTE from pig thyroid glands.

It is a much older treatment than levothyroxine and was the main treatment for hypothyroidism from the early 1890s until the 1970s. Since then, most people have replaced thyroid hormones with levothyroxine.

According to a 2020 study, many people use NDTs to manage their hormone levels. However, 80% of people who responded to the survey reported that NDTs were effective at relieving hypothyroidism symptoms and correcting thyroxine levels. Of these, 77% stated they preferred NDTs to previous therapies.

A healthcare professional may prescribe Armour Thyroid for people who do not seem to respond to levothyroxine. However, Armour Thyroid was available before 1938 — the year the FDA began to regulate drug ingredients and marketing.

As a result, the FDA “grandfathered” NDTs into approval, meaning they did not need to meet the same safety standards and labeling as more modern medications.

According to the FDA, doses may vary between batches and even individual tablets. The body is sensitive to even minor changes in thyroid hormone levels, with too little not having the desired effect and too much risking severe side effects in some people.

The manufacturing process is also more complex than levothyroxine, so there may be concerns around effectiveness, quality, and safety.

Learn more about Armour Thyroid.

Thyroid hormone medications are important for restoring hormone levels and preventing complications. However, they may cause adverse effects in some people.


Common side effects of levothyroxine include:

A person should contact a medical professional if these side effects worsen or do not resolve. They may need to reduce the dosage.

The following side effects require immediate or emergency medical attention:

  • shortness of breath
  • flushing
  • hives
  • itching
  • nausea
  • rash
  • stomach pain
  • swelling of the ankles, feet, hands, or lower legs
  • wheezing

Armour Thyroid

The main side effects of people who use Armour Thyroid to treat hypothyroidism include:

Other side effects of Armour Thyroid often occur when a person receives a dosage that is too high. This might lead to thyroid hormone toxicity, which can lead to the following symptoms:

  • a faster heartbeat or pulse
  • sweating
  • an inability to tolerate heat
  • chest pain
  • anxiety or nervousness

Children who take Armour Thyroid may experience hair loss but usually recover without treatment. Symptoms of an Armour Thyroid overdose may include:

  • a sudden increase in body temperature, or fever
  • a drop in blood sugar
  • dehydration

The following are common questions about hypothyroidism medications.

Does levothyroxine cause weight gain?

Weight gain is a possible side effect of taking levothyroxine.

Is there a downside to taking thyroid medication?

People with hypothyroidism need to take thyroid medication for the rest of their lives. While side effects may occur, these are usually only when a person takes too much. However, any side effects that occur with regular usage of the medications are generally mild.

All medication has a risk of side effects. Taking thyroid medication can reduce the risk of hypothyroidism complications, such as goiter, heart and kidney problems, and a life threatening condition called myxedema coma.

What should I avoid while taking levothyroxine?

Many medications can interact with levothyroxine in harmful ways. It is especially important to avoid those in the “Important warnings” section of the label. These include the following medications, as well as others:

  • amiodarone (Nexterone, Pacerone)
  • androgens, such as nandrolone and testosterone (Androderm)
  • antacids containing aluminum or magnesium (Maalox, Mylanta)
  • beta-blockers, such as metoprolol (Lopressor), propranolol (Inderal, Innopran), or timolol
  • blood thinners, including heparin or warfarin (Coumadin, Jantoven)
  • carbamazepine (Carbatrol, Equetro, Tegretol, Teril)
  • corticosteroids, including dexamethasone
  • digoxin (Lanoxin)
  • methadone (Methadose)

People who take thyroid medications should disclose this to a healthcare professional before taking any other medications.

The main medication for hypothyroidism is levothyroxine, a synthetic thyroid hormone replacement.

Some people use a pig-derived natural desiccated thyroid medication called Armour Thyroid. However, this existed before the regulatory practices of the FDA and is not currently FDA-approved for the treatment of hypothyroidism. For this reason, ensuring high quality, consistent doses is difficult.

However, either medication generally only causes side effects if a person receives too high a dose or takes another medication that could lead to possible interactions. Before taking thyroid medications, a person should discuss potential side effects and interactions with a healthcare professional.