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Symptoms Of Too Much Thyroid Medication

Learn about the symptoms and causes of overmedication and tips to prevent taking too much thyroid medication.
Symptoms Of Too Much Thyroid Medication
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If you live with an underactive thyroid, you likely take thyroid hormone replacement medication. And your provider may have had to adjust your dose one or more times before getting it right. 

Did you know that taking too much thyroid medication can cause more harm than good? Indeed, too much thyroid medication can cause hyperthyroidism, a state of an overactive thyroid. Like hypothyroidism, hyperthyroidism can have damaging effects on your body and mind.

How thyroid hormone medication treats hypothyroidism

The thyroid gland regulates cellular metabolism, growth, and development. When the thyroid does not produce enough thyroid hormone, it can slow down all your body systems.

Thyroid hormone replacement medications help restore your thyroid hormone levels. They do this by replacing the amount of thyroid hormone your thyroid can no longer make. In turn, your body can return to optimal function.

Thyroid hormone replacement medication can improve your overall health and quality of life and relieve symptoms of hypothyroidism, including:

But, taking thyroid hormone replacement medications will not cure hypothyroidism. Those with hypothyroidism generally need life-long treatment. If you were to stop taking your medication (not recommended unless under your provider’s supervision), your hypothyroidism symptoms would return.

Which medications treat hypothyroidism?

The thyroid gland produces two hormones: thyroxine (T4) and triiodothyronine (T3). When you have healthy thyroid function, the inactive T4 hormone is released into circulation and then converted into the active T3 hormone necessary to power your metabolism at the cellular level.

Thyroid hormone replacement medication also comes in T4 and T3 forms.  Often, treatment for thyroid replacement starts with synthetic T4 drugs, and this therapy assumes that your body can successfully convert T4 to T3. The synthetic version of T4 is called levothyroxine (generic), and there are also brand-name versions of levothyroxine, including Synthroid, Levoxyl, Unithroid, and Euthyrox. These forms of levothyroxine are available as a tablet. Another brand, Tirosint, is a gel capsule, and Tirosint-SOL is a liquid formulation for people with allergies, malabsorption, or trouble taking pills.

What if your body has difficulty converting T4 to T3, or you take a medication that can interfere with absorption of the T4-only medication? In that case, levothyroxine may not be enough for you. For those whose symptoms aren’t relieved with T4-only preparations, adding T3 to your medication regimen may be necessary. The T3-only formulations on the market include liothyronine (generic) and the brand-name Cytomel.

Combination therapies that contain both T4 and T3 are also available. There are three main ways that combination therapy is prescribed. 

  • A prescription for both levothyroxine and liothyronine, either generic or brand names
  • Natural desiccated thyroid (NDT) comes from the dried (desiccated) thyroid glands of pigs and includes natural forms of T4 and T3. Common NDT medications include Armour, Nature-Throid, NP Thyroid, and Adthyza.
  • Compounded thyroid medication is a personalized medication in which drug ingredients are combined, mixed, or altered to solve specific patient needs. A specialty compounding pharmacy must prepare these medications.

When you start thyroid hormone replacement therapy, it usually takes a few weeks to see an improvement in your symptoms. Your provider will likely need to adjust your dosing to reach a therapeutic level.

Symptoms of excess thyroid hormone medication

Sometimes, the dose of your thyroid hormone replacement medication may be too high.  When your dose is too high, your T4 levels rise above the normal range, resulting in hyperthyroidism symptoms. When you’re hyperthyroid, your metabolic processes speed up, causing symptoms opposite to what you see in hypothyroidism. Common symptoms of hyperthyroidism include:

  • A rapid heartbeat 
  • Sweating or heat intolerance
  • Elevated body temperature
  • Weight loss
  • Irritability
  • Insomnia
  • Brittle hair
  • Thinning skin
  • Frequent bowel movements (usually not diarrhea)

Sometimes, hyperthyroidism symptoms are the same as the ones you may experience when you have low thyroid hormones. Overlapping symptoms include exhaustion, muscle aches, and feelings of jittery and nervousness. Some people even describe their symptoms as flu-like.

What causes high T4 levels? How can you prevent overmedication?

There are several reasons why your T4 levels may become too high, causing symptoms of hyperthyroidism. Sometimes, it isn’t just one reason but a combination of reasons that cause a jump in T4 levels. 

Dose titration

The dose titration process means your provider increases your thyroid medication dose based on your thyroid test results. If the titration process happens too quickly, T4 levels may jump too high as your body may still be adjusting to the previous dose. It takes weeks to months for your body to adapt to a new dose.

It is important to tell your provider if you missed doses of your thyroid medication (it happens to everyone), especially during the titration phase. Missed doses of thyroid hormone can lead to an inaccurate measurement of your thyroid hormone levels. As a result, your healthcare provider may have the impression you need a higher dose when, in reality, you may not.

Variability in drug quality

Every thyroid medication contains a slightly different amount of thyroid hormone. Because of this, people with hypothyroidism should stay with the same manufacturer when refilling a  prescription. But sometimes, it’s unavoidable, and you must take what the pharmacy gives you. (For example, when you are taking generic levothyroxine.) 

If your medication looks different, then your manufacturer may have changed. However, it is always best to check with your pharmacist. If this is the case and your preferred manufacturer is unavailable, call your provider’s office to inform them about the switch. They may have you come in for a recheck of your thyroid function levels in a few months.

Dietary changes

Certain foods can increase or decrease how much thyroid hormone your body absorbs. Whole grains and soy-containing products can block your body from absorbing thyroid medication. The same is true for certain fruit juices and coffee. A sudden change in your diet can also influence thyroid medication absorption. For example, if you stop eating a high-fiber diet, you may absorb more of your dose. Your dose is, for practical purposes, higher because more T4 ends up in circulation, which can then lead to symptoms of hyperthyroidism.

In some cases, taking a high dose of iodine – usually in the form of iodine, kelp, or bladderwrack supplements –  can trigger excess thyroid hormone production. 

Because your food and drink choices can impact the absorption of your thyroid hormone medication and your thyroid levels, take your medication on an empty stomach. Ideally, this is 30 minutes to 1 hour before your first meal, including your morning coffee, or at least 2 hours after your last meal. It is essential to be consistent in how and when you take your thyroid medication.

Medications and supplements

You may have seen certain over-the-counter supplements that promise to boost your thyroid function. Sometimes, these supplements contain “thyroid glandular” or pieces of thyroid tissues from animals. Other times, they may include actual thyroid hormone. As a result, your thyroid hormone levels may increase in your body. When thyroid glandular supplements are combined with thyroid hormone replacement medications, you are at a greater risk for high T4 levels.

Similarly, certain medications can alter how much of your thyroid medication your body absorbs. These medications include protein pump inhibitors, iron, and antacids containing calcium or aluminum. Estrogen replacement therapy and birth control pills with estrogen may also affect your thyroid medication dose.

Because of these reasons, talk with your provider before starting or stopping over-the-counter supplements and medications. They may want to proactively adjust your thyroid medication dose or recheck your thyroid function in a few months.


Your thyroid hormone requirements increase when you are pregnant. Because of this, your provider will likely check your thyroid biomarkers more frequently and increase your dose of thyroid replacement medication while pregnant.

Once you have your baby, your provider usually needs to lower your dose. This drop in dosage helps prevent your thyroid hormone levels from going too high during the postpartum period.

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A note from Paloma Health

It’s never a good idea to abruptly stop your thyroid medication, even if you are experiencing symptoms of hyperthyroidism.

Contact your thyroid provider if you suspect your thyroid medication dose is too high. Your provider should order a thyroid blood test to assess your thyroid biomarkers, or you can test it from home using Paloma’s convenient at-home testing kit. Our testing kit monitors the three most common thyroid biomarkers – thyroid-stimulating hormone (TSH), T4, and T3 – along with thyroid peroxidase (TPO) antibodies.

If you are experiencing thyroid overmedication, your TSH test will likely be on the lower end of the reference range, with T4 and T3 levels on the upper end of the reference range.

It is also helpful to track your symptoms to log what you are experiencing and what time of day. This information helps your provider assess factors such as absorption issues that may not appear in your blood work. As mentioned above, tell your provider if you start or stop any supplements or medications or have missed many doses in a row.

If you don’t have a provider that specializes in hypothyroidism, consider setting up a free consultation with one of Paloma’s team of nationally recognized thyroid experts.

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Medline Plus. Hypothyroidism. Published 2019. Accessed October 6, 2023.

Medline Plus. Hyperthyroidism. Published 2019. Accessed October 6, 2023.

Jonklaas J, Bianco AC, Bauer AJ, Burman KD, Cappola AR, Celi FS, et al. Guidelines for the treatment of hypothyroidism. Thyroid. 2014; 24(12): 1670 - 1751. doi:

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Emilie White, PharmD

Clinical Pharmacist and Medical Blogger

Emilie White, PharmD is a clinical pharmacist with over a decade of providing direct patient care to those hospitalized. She received her Doctor of Pharmacy degree from Massachusetts College of Pharmacy and Health Sciences. After graduation, Emilie completed a postgraduate pharmacy residency at Bon Secours Memorial Regional Medical Center in Virginia. Her background includes caring for critical care, internal medicine, and surgical patients.

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