Herb & supplement monograph

Thyroid Extract Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Thyroid Extract interacts with medications. The heart of this page is the interaction list — every drug Thyroid Extract is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Thyroid Extract is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Thyroid Extract Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Thyroid Extract drug interaction appears low for most people. None of the listed interactions are rated major, and nearly all of the many medications on the list fall into the minor category.

Interactions deserving the most attention

The combination that deserves the most care is with levothyroxine and other thyroid hormone medications. Because thyroid extract itself supplies the thyroid hormones T3 and T4, taking it alongside levothyroxine could push hormone levels too high and add to side effects, though this concern is based mostly on theory rather than firm human studies. Separately, the best-documented finding is that many oral medications, along with foods and products containing minerals like calcium or iron, can bind thyroid hormones in the gut and reduce how well they are absorbed, which can make the extract less effective rather than more dangerous.

What the rest of the list means

The long list of interacting medications reflects this absorption issue more than genuine harm. Most entries are minor, and for the great majority of people they signal a possible dip in effectiveness, not a safety threat. The one moderate concern with thyroid medicines remains theoretical and has not been confirmed in well-controlled human studies.

Check your medications against Thyroid Extract

Based on HelloPharmacist’s Thyroid Extract interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Thyroid Extract

2022 medications have a known interaction with Thyroid Extract, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Thyroid Extract using our pharmacist-reviewed interaction data.

AI summaries are generated from our Thyroid Extract interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Thyroid Extract combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Thyroid Extract affects

Every type of medication (drug category) Thyroid Extract is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 2 drug categories Thyroid Extract interacts with

Levothyroxine (synthroid, Others)Oral Drugs

Levothyroxine (Synthroid, Others)

Theoretically, thyroid extract might increase the effects and adverse effects of levothyroxine.
Thyroid extract contains triiodothyronine (T3) and thyroxine (T4). Taking thyroid extract increases blood levels of T3 and T4, in some cases to abnormally high levels.

Likelihood Possible Evidence D

Oral Drugs

Food and medications can interfere with thyroid hormone absorption. Some foods, particularly those high in fiber or containing certain minerals like calcium or iron, can bind to thyroid hormones and reduce their absorption in the digestive tract. Additionally, taking thyroid medications with certain drugs, like antacids or calcium supplements, can hinder the effectiveness of the thyroid medication, necessitating adjustments in dosage or timing. Prescription thyroid medications, such as Synthroid, are recommended to be taken on an empty stomach, at least 30 minutes before food and other medications, for optimal absorption.

Likelihood Likely Evidence A

Monograph

Thyroid Extract: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Thyroid extract supplements are made from dried animal thyroid gland and may contain real thyroid hormones (T3 and T4), but the amounts in over-the-counter products are not standardized and can be unpredictable. Self-treating a thyroid problem with these supplements can be risky, so always work with a doctor or pharmacist and use prescription thyroid medicine when treatment is needed.

Part used: Animal thyroid gland tissue (commonly from pigs or cows)
Common forms: Capsules, tablets, dried powder

People commonly use it for

Hypothyroidism (underactive thyroid)
Fatigue and low energy
Weight management
Sluggish metabolism
General thyroid support

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

OTC thyroid extracts may contain active hormones in unknown amounts and should not be used without medical supervision.

PregnancyInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Thyroid extract is a dietary supplement made from the thyroid gland of animals, usually pigs (porcine) or cows (bovine). The gland tissue is dried and ground into a powder, then put into capsules or tablets. Because it comes from a real thyroid gland, it can contain the natural thyroid hormones triiodothyronine (T3) and thyroxine (T4).

People most often take thyroid extract hoping to support an underactive thyroid or to boost energy, metabolism, and weight loss. It is important to know that there is a big difference between prescription "desiccated thyroid" products, which are regulated and dose-controlled, and over-the-counter "glandular" supplements, which are not. OTC products may have their hormone content reduced during processing, but testing has found that some still contain meaningful amounts of hormone.

Because the amount of active hormone is inconsistent and often unlabeled, the use of these supplements is controversial among healthcare professionals.

How it works

The thyroid gland naturally makes two key hormones, T4 and T3, which control how fast your body uses energy (your metabolism). In true hypothyroidism, the body does not make enough of these hormones, and replacing them can relieve symptoms.

Because thyroid extract is made from actual animal thyroid tissue, it can supply these hormones directly. This is the same general idea behind prescription desiccated thyroid. The problem with supplements is that the amount of hormone is not standardized, so one capsule or batch may differ from another. This makes it hard to get the right, steady dose your body needs.

Effectiveness

Does Thyroid Extract work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 3 uses evaluated

3 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Thyroid Extract, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 3 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Hypothyroidism

Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral thyroid extract for hypothyroidism, there is insufficient reliable information about the clinical effects of thyroid extract for this purpose.

Insufficient Reliable Evidence To Rate Infertility

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral thyroid extract is beneficial in females with infertility.

Insufficient Reliable Evidence To Rate Thyroid cancer

Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral thyroid extract after treatment for thyroid cancer, there is insufficient reliable information about the clinical effects of thyroid extract for this purpose.

Source & disclaimer. Effectiveness ratings and evidence summaries are provided by Natural Medicines (Therapeutic Research Center) and shown as licensed. Where Natural Medicines hasn’t rated a use, HelloPharmacist’s pharmacists may add their own reviewed rating and evidence (each such entry is labeled). This is educational information, not medical advice — talk with your pharmacist or doctor before starting, stopping, or changing a supplement.

Safety & precautions

The biggest safety concern is that you may be taking real thyroid hormone without knowing how much. Too much thyroid hormone can cause hyperthyroidism, which can lead to a fast or irregular heartbeat, anxiety, trouble sleeping, weight loss, and over the long term, weakened bones (osteoporosis) and heart rhythm problems like atrial fibrillation.

People with heart disease, high blood pressure, diabetes, or existing thyroid conditions should be especially careful and should not use these products without close medical supervision. Older adults are also at higher risk of side effects.

There is also a small theoretical concern about disease transmission from animal tissue. For pregnancy and breastfeeding, thyroid hormone levels must be tightly controlled, and unregulated extracts could harm the parent or baby — so these supplements should be avoided unless a doctor specifically prescribes a regulated thyroid product. Anyone with thyroid symptoms should get proper blood tests rather than self-treat.

Side effects

Side effects usually come from getting too much thyroid hormone. These can include:

Rapid, pounding, or irregular heartbeat
Feeling anxious, jittery, or shaky
Trouble sleeping
Sweating and feeling overheated
Unintended weight loss
Headache, diarrhea, or upset stomach

More serious risks with long-term overexposure include bone loss and dangerous heart rhythm problems. If you have chest pain, a very fast or irregular heartbeat, or severe symptoms, stop the product and seek medical care right away.

Thyroid Extract: Reported Adverse Effects

Documented safety reports on Thyroid Extract from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

Orally, thyroid extract may be unsafe due to hormone potency inconsistencies.

Most Common Adverse Effects:

Orally: Elevated levels of triiodothyronine (T3) and/or thyroxine (T4).

Serious Adverse Effects (Rare):

Orally: Thyroid storm or thyrotoxic crisis.

Reports by condition

Allergic rhinitis (hay fever) Immunologic

A 30-year-old female with allergic rhinitis and multinodular goiter developed allergic urticaria after treatment with desiccated thyroid extract.

Benvenga, S., Trimarchi, F., Barbera, C., Costante, G., Morabito, S., Barberio, G., and Consolo, F. Circulating immunoglobulin E (IgE) antibodies to L-thyroxine in a euthyroid patient with multinodular goiter and allergic rhinitis. J Endocrinol Invest 198

Allergic rhinitis (hay fever) Dermatologic

In one case report, a teenage female taking thyroid extract developed multiple nevi on the skin. In another case report, a 30-year-old female with allergic rhinitis and multinodular goiter developed allergic urticaria after treatment with desiccated thyroid extract.

Hypertension Endocrine

Clinical research shows that many patients treated with thyroid extract experience abnormally high levels of triiodothyronine (T3) and/or thyroxine (T4). In some patients, these elevated hormone levels result in thyrotoxic crisis or thyroid storm, with symptoms including nausea, vomiting, myalgia, fever, tachycardia, hypertension, agitation, and altered mental state. In one case, a healthy 62-year-old female took a thyroid extract that was accidentally compounded to provide T3 and T4 at levels of 720,000 and 30,000 micrograms, respectively, daily. The patient required plasmapheresis for two days to reduce levels of T3 and T4 and reduce the symptoms of thyroid storm.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

Adverse-effects data: Natural Medicines, Therapeutic Research Center

Dosing

There is no established or standardized safe dose for over-the-counter thyroid extract supplements, partly because their hormone content varies from product to product. This is a major reason healthcare providers are cautious about them.

If thyroid hormone replacement is truly needed, it should be prescribed and monitored by a doctor, often with regular blood tests to fine-tune the dose. If you choose to use a supplement, follow the product label exactly and talk with a pharmacist or doctor first. Never adjust or stop prescription thyroid medicine on your own.

Pregnancy & Breastfeeding

Thyroid Extract & Pregnancy

Insufficient reliable information

Insufficient reliable information available; avoid using.

Thyroid Extract & Breastfeeding

Insufficient reliable information

Insufficient reliable information available; avoid using.

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 6 references that drive our Thyroid Extract monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

Benvenga, S., Trimarchi, F., Barbera, C., Costante, G., Morabito, S., Barberio, G., and Consolo, F. Circulating immunoglobulin E (IgE) antibodies to L-thyroxine in a euthyroid patient with multinodular goiter and allergic rhinitis. J Endocrinol Invest 198 PubMed
Gerard, P., Malvaux, P., and De Visscher, M. Accidental poisoning with thyroid extract treated by exchange transfusion. Arch Dis Child 1972;47(256):981-982. PubMed
Tofahrn, J. and Hundeiker, M. [Nevus eruption following thyroidin with spontaneous involution]. Z Hautkr 1976;51(15):617-620.
Rees-Jones RW, Larsen PR. Triiodothyronine and thyroxine content of desiccated thyroid tablets. Metabolism 1977;26(11):1213-1218. PubMed
Jackson IM, Cobb WE. Why does anyone still use desiccated thyroid USP? Am J Med 1978;64(2):284-8. PubMed
Jha S, Waghdhare S, Reddi R, Bhattacharya P. Thyroid storm due to inappropriate administration of a compounded thyroid hormone preparation successfully treated with plasmapheresis. Thyroid. 2012;22(12):1283-6. PubMed

Keep reading

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

Pharmacist Counseling Corner

Thyroid Extract: Common Questions

What is Thyroid Extract used for, and does it work?

People use Thyroid Extract for a range of reasons, but according to the Natural Medicines database the current clinical evidence is insufficient to confirm it works for the specific conditions it has been studied for. See the graded list on this page, and talk to your pharmacist or doctor before relying on it for any condition.

Does Thyroid Extract interact with prescription medications?

Yes. We list 2022 medications with a known interaction with Thyroid Extract. Use the checker above to see how Thyroid Extract interacts with a specific drug.

How are Thyroid Extract interactions rated?

Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.

Is it safe to take Thyroid Extract with my medications?

It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.

Where does this Thyroid Extract interaction information come from?

Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.

Is Thyroid Extract the same as prescription thyroid medicine?

Not exactly. Prescription desiccated thyroid is regulated and dose-controlled, while over-the-counter "thyroid support" glandular supplements are not standardized and may contain unknown amounts of hormone. They should not be treated as interchangeable.

Can I use Thyroid Extract to lose weight or boost energy?

Using Thyroid Extract for weight loss or energy when you don't have a thyroid problem is not supported by good evidence and can be dangerous, since extra thyroid hormone can strain your heart and bones. It's best to find out the real cause of your symptoms with a doctor.

Is Thyroid Extract safe to take on my own?

Self-treating with Thyroid Extract is risky because you may be getting active hormone in unpredictable amounts. Thyroid problems should be diagnosed with blood tests and managed by a healthcare provider.

Can I take Thyroid Extract during pregnancy or while breastfeeding?

No, you should avoid unregulated Thyroid Extracts during pregnancy and breastfeeding. Thyroid hormone levels need careful control during these times, so any treatment should be a regulated medicine prescribed and monitored by your doctor.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Thyroid Extract Drug Interactions, Uses, Effectiveness, Safety & More

Your Choice:

Thyroid Extract Drug Interactions: The Bottom Line

Drugs that interact with Thyroid Extract

Don’t want to scroll the list? Just ask.

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Likelihood — How Well It’s Documented

Where This Data Comes From

The kinds of drugs Thyroid Extract affects

Thyroid Extract: Uses, Safety & Side Effects

Overview

How it works

Does Thyroid Extract work?

Safety & precautions

Side effects

Thyroid Extract: Reported Adverse Effects

Dosing

Thyroid Extract & Pregnancy

Thyroid Extract & Breastfeeding

References & further reading

Thyroid Extract: Common Questions

Related supplements & herbs

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