What meds should I avoid with hyperthyroidism? A guide to safe medication use

October 8, 2025 •

4 min read

Approximately 1.2% of the U.S. population suffers from hyperthyroidism, and managing it safely requires knowledge of drug interactions. Understanding what meds should I avoid with hyperthyroidism is critical to preventing complications and ensuring effective treatment.

Quick Summary

Navigating medication choices with an overactive thyroid requires careful consideration of potential risks and interactions. This article details prescription, OTC, and supplemental drugs to avoid for safety.

Key Points

Amiodarone risk: Due to its high iodine content, the heart medication amiodarone can cause or worsen hyperthyroidism, necessitating careful monitoring.
Avoid decongestants: OTC decongestants with pseudoephedrine or phenylephrine can dangerously increase heart rate and blood pressure in hyperthyroid patients.
Excess iodine is harmful: Supplements containing excessive iodine (e.g., kelp) or iodine-based cough medicines should be avoided, as they can overstimulate the thyroid gland.
Beware of supplements: Supplements containing L-tyrosine or certain herbs like licorice extract can negatively impact thyroid function and should be used with caution.
Biotin affects lab tests: High-dose biotin can interfere with thyroid function test results, potentially leading to misdiagnosis or treatment adjustments based on inaccurate information.
Inform your doctor: Always tell all your healthcare providers about your hyperthyroidism to ensure that any prescribed medication is safe and appropriate for your condition.
Exercise caution with imaging: Alert doctors about your hyperthyroidism before receiving any imaging with iodine-based contrast agents.

An overactive thyroid, or hyperthyroidism, accelerates the body's metabolism, affecting numerous systems, including the cardiovascular system. This heightened state makes individuals particularly sensitive to certain medications and supplements. Interactions can worsen symptoms like a rapid heartbeat, anxiety, and weight loss, and in some cases, can trigger a life-threatening complication called a thyroid storm. Both prescription and over-the-counter (OTC) drugs carry risks that demand careful attention. Consulting with a healthcare provider before starting any new medication is paramount for individuals with hyperthyroidism.

Prescription Medications to Avoid or Use with Caution

Certain prescription drugs are known to interfere with thyroid function or exacerbate hyperthyroid symptoms. For some, the risks are due to high iodine content, while others affect hormonal pathways or have stimulating side effects.

Iodine-Rich Drugs

Amiodarone: This potent anti-arrhythmic medication, used for heart rhythm disorders, contains extremely high levels of iodine, which can be 50 to 100 times the daily recommended intake. In individuals with hyperthyroidism, this excess iodine can trigger or worsen the condition. Regular thyroid monitoring is essential for anyone taking amiodarone.
Contrast Media: Certain X-ray contrast agents, used during imaging procedures, contain high levels of iodine. For patients with pre-existing thyroid nodules, this can cause an overproduction of thyroid hormones, leading to or exacerbating hyperthyroidism. Your doctor should be aware of your thyroid status before you undergo any such tests.

Cancer and Immunotherapy Medications

Immune Checkpoint Inhibitors: Used in cancer treatment, these drugs (such as nivolumab and pembrolizumab) can induce immune-related adverse effects, including thyroid dysfunction like Graves' disease.
Alemtuzumab: Another cancer medication, alemtuzumab, has been linked to an increased risk of developing Graves' disease.
Interferon-alpha: This medication, used for chronic hepatitis C, can lead to thyroid disease, including hyperthyroidism, in a significant percentage of patients.

Psychiatric and Other Medications

Lithium: Used as a mood stabilizer, lithium can affect thyroid function, and in rare cases, lead to hyperthyroidism or Graves' disease.
Sympathomimetics: Medications like epinephrine, sometimes used in local anesthetics or for other cardiac issues, can cause cardiovascular stimulation that is dangerous for severely hyperthyroid individuals.
Estrogens: Oral contraceptives and hormone replacement therapy containing estrogen can increase thyroxine-binding globulin (TBG), potentially altering thyroid hormone levels and requiring dosage adjustments.

Over-the-Counter (OTC) Drugs and Supplements to Avoid

Even common, non-prescription products can pose significant risks for individuals with hyperthyroidism.

OTC Drugs

Decongestants: Many cold, flu, and allergy remedies contain decongestants like pseudoephedrine or phenylephrine. These can increase heart rate and blood pressure, posing a risk of cardiac complications for those with an already accelerated cardiovascular system due to hyperthyroidism.
Iodine-Containing Products: Some cough syrups and skin antiseptics (like povidone-iodine) contain iodine. Excess iodine intake can trigger or worsen hyperthyroidism, especially in susceptible individuals.

Supplements

Excessive Iodine and Kelp: High-dose iodine supplements or kelp-based products should be strictly avoided. While iodine is essential, excessive amounts can cause the thyroid gland to produce too much hormone.
L-Tyrosine: This amino acid is a precursor to thyroid hormones. Supplementing with L-tyrosine can increase hormone production, which is detrimental for hyperthyroid patients.
Licorice Extract and Other Herbs: Licorice extract can increase cortisol levels, which is not ideal for hyperthyroidism management. Other herbs like celery extract have also been shown to affect thyroid function.
Over-the-Counter Thyroid Glandular Supplements: These are unregulated and contain unpredictable amounts of animal thyroid hormone, which can worsen hormone imbalances and interact negatively with other medications.
Biotin: While not directly harmful to the thyroid, high doses of biotin can interfere with thyroid lab tests, leading to inaccurate results. Patients should stop taking biotin at least a few days before having their thyroid levels tested.

Important Drug Interactions and Management Strategies

Understanding the mechanisms behind drug interactions is crucial for safe management. Hyperthyroidism can affect the metabolism of other drugs, necessitating careful dosage adjustments and professional guidance.

Medication Comparison: Safe vs. Risky Choices for Hyperthyroidism


Medication Category	Risky/Contraindicated Examples	Safe/Alternative Examples
Heart Rhythm Drugs	Amiodarone	Beta-blockers (e.g., atenolol, propranolol) are used therapeutically to manage hyperthyroid symptoms.
Decongestants	Pseudoephedrine, Phenylephrine (many OTC cold/flu formulas)	Saline nasal sprays, humidifiers, or steam inhalation for congestion.
Supplements	High-dose Iodine, Kelp, L-Tyrosine	Selenium, provided it is not in excess, and under a doctor's supervision.
Imaging Agents	Iodine-containing contrast media	Non-iodinated contrast agents (MRI with gadolinium contrast).
Pain Relievers	High-dose Salicylates (aspirin)	Standard doses of acetaminophen (Tylenol).

Conclusion

Living with hyperthyroidism requires vigilant management, particularly concerning medication and supplement use. As explored, a range of substances, from prescription drugs like amiodarone to common OTC decongestants and herbal supplements containing excess iodine or L-tyrosine, can significantly impact thyroid function and cardiovascular health. The accelerated metabolism caused by hyperthyroidism makes the body more sensitive to certain compounds, highlighting the need for careful consideration. Patients should always consult their endocrinologist or primary care physician before taking any new medication or supplement to review potential risks and interactions. In addition to a professional’s guidance, becoming an informed patient by carefully reading labels, especially for OTC products, is a crucial step toward ensuring safety and preventing severe complications like a thyroid storm. For comprehensive information on drugs affecting thyroid function, an authoritative resource can be found via the National Institutes of Health.

Frequently Asked Questions

It is generally not recommended to take decongestants like pseudoephedrine or phenylephrine if you have hyperthyroidism. These ingredients can increase your heart rate and blood pressure, which poses a significant risk to your already sensitive cardiovascular system.

Amiodarone is a heart medication that contains a very high concentration of iodine. Since iodine is used by the thyroid gland to produce hormones, the excess iodine from amiodarone can cause or worsen hyperthyroidism.

You should not cut iodine completely out of your diet, but you should avoid consuming it in excessive amounts. This means steering clear of high-dose iodine supplements (like kelp) and certain medications or antiseptics containing iodine.

L-tyrosine is an amino acid that the body uses to produce thyroid hormones. Taking L-tyrosine supplements could increase your thyroid hormone production, worsening your hyperthyroidism.

High doses of biotin can interfere with the lab tests used to monitor your thyroid hormone levels. This can lead to false readings that could result in incorrect treatment decisions. You should stop taking biotin for a few days before any thyroid blood tests.

Oral contraceptives containing estrogen can affect thyroid hormone binding, which might alter your thyroid hormone levels. You may require a dosage adjustment to your thyroid medication if you start or stop estrogen therapy.

Yes, some cancer immunotherapy drugs, such as checkpoint inhibitors and alemtuzumab, can trigger thyroid dysfunction, including hyperthyroidism or Graves' disease.

While high doses of salicylates (like aspirin) should be used with caution, standard doses of acetaminophen (Tylenol) are generally considered safe for pain relief with hyperthyroidism.