Drug & supplement interaction

Thyroid Extract + Levothyroxine Sodium

Levothyroxine Sodium brand names: Tirosint-Sol, Thyquidity, Ermez.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Levothyroxine Sodium falls into 2 drug categories that Thyroid Extract can interact with; the most serious is rated moderate. Theoretically, thyroid extract might increase the effects and adverse effects of levothyroxine.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Thyroid Extract and Levothyroxine Sodium

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Thyroid Extract interacts with whole categories of medication. Levothyroxine Sodium falls into 2 of those categories, so it can interact with Thyroid Extract in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

LEVOTHYROXINE (Synthroid, others)

1 of 2
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.
Severity Moderate Likelihood Possible Evidence D

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.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version: levothyroxine is a thyroid hormone (man-made T4), and thyroid extract from animal glands also contains thyroid hormones (T3 and T4). So if you take both, you're essentially stacking thyroid hormone on top of thyroid hormone. That can push your levels higher than intended.

When thyroid levels run too high, you may notice a racing or pounding heart, jitteriness, trouble sleeping, sweating, shakiness, or unexpected weight loss. Over time, too much can also stress your heart and bones. The catch with thyroid extract is that the hormone amounts aren't standardized, so the dose is unpredictable. This concern is based on how these products work rather than hard studies, but it's a real one. Please don't change anything on your own. Talk with your pharmacist or doctor first so your dose stays right.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. 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
  2. Rees-Jones RW, Larsen PR. Triiodothyronine and thyroxine content of desiccated thyroid tablets. Metabolism 1977;26(11):1213-1218. PubMed
  3. Jackson IM, Cobb WE. Why does anyone still use desiccated thyroid USP? Am J Med 1978;64(2):284-8. PubMed
  4. 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
Minor

Oral Drugs

2 of 2

Why this applies to Levothyroxine Sodium

Levothyroxine Sodium falls under Oral Drugs — the group Thyroid Extract interacts with.

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.
Severity Minor Likelihood Likely Evidence A

Well-controlled human studies have demonstrated the likely existence of this interaction.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the key thing to understand: levothyroxine is itself a thyroid hormone (T4), and thyroid extract also contains real thyroid hormones (T4 and T3). So if you take both, you're essentially stacking thyroid hormone on top of thyroid hormone. The bigger concern isn't poor absorption here, it's getting too much. Layering an unpredictable, unstandardized supplement onto your prescription dose can push you into overtreatment.

When thyroid levels run too high, you may notice a racing or pounding heart, shakiness, trouble sleeping, feeling hot or sweaty, weight loss, or anxiety. Your carefully dialed-in levothyroxine dose can be thrown off. Please don't add thyroid extract on your own. Talk with your doctor or pharmacist first so your levels stay where they should be.

Contact Dr. Brian directly if you have additional questions on this interaction

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction 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.
  • PossibleInteraction 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.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Thyroid Extract Also Interacts With Other Medications

Thyroid Extract has 2 moderate, 2,019 minor known drug interactions in our database — the Levothyroxine Sodium one above is among them. If you take anything else, check it against the full list below.

Moderate 2 Minor 2,019 No known interaction 809 (incl. Levothyroxine Sodium)
Taking anything else?

Check Another of Your Medications Against Thyroid Extract

Covers the 2,830 medications we’ve checked against Thyroid Extract. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Levothyroxine Sodium

This page covers Thyroid Extract only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Levothyroxine Sodium page lists 50 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Tiratricol (major), Acetyl-l-carnitine (moderate), Alpha-lipoic Acid (moderate) and Ascophyllum Nodosum (moderate).

Open the Levothyroxine Sodium interaction page

How much people look this up

Where Thyroid Extract and Levothyroxine Sodium Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Thyroid Extract
Steady interest

#880 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Levothyroxine Sodium
Top 5%

#132 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Thyroid Extract

What is Thyroid Extract?

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

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.

Read the full Thyroid Extract monograph & all interactions
Keep checking

Other Drugs & Thyroid Extract

Browse every other medication we’ve checked against Thyroid Extract — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
2Moderate
2,019Minor
808No known interaction
2 Moderate 2,019 Minor 808 No interaction
Moderate

2 interactions

Minor

2,019 interactions

Showing 60 of 2,019 minor interactions — see all 2,019 on the Thyroid Extract page.

No interaction 808 drugs checked — show the list

We also checked Thyroid Extract against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 808 medications checked with no known interaction — see the full Thyroid Extract list.

See the full Thyroid Extract interactions page
See every supplement checked against Levothyroxine Sodium, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

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.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Thyroid Extract monograph › Uses, safety, and every drug interaction in one place Levothyroxine Sodium supplement interactions › Every supplement checked against Levothyroxine Sodium, ranked by severity Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Thyroid Extract and Levothyroxine Sodium Together: Common Questions

Can you take Thyroid Extract with Levothyroxine Sodium?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Thyroid Extract and Levothyroxine Sodium?
Levothyroxine Sodium belongs to more than one drug category, and Thyroid Extract interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Thyroid Extract and Levothyroxine Sodium interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

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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.