Thyroid Glandular and "T3" Supplements: What's in Them, and Why It Matters if You Take Levothyroxine

Thyroid glandular supplements are made from dried animal thyroid, usually from cows or pigs, and thyroid tissue naturally holds thyroid hormone. When US researchers tested supplements sold for "thyroid support", most contained real T3 or T4, some at levels comparable to prescription doses. If you take levothyroxine, that is an unmeasured extra dose that can push your levels too high and make your results harder to read. In Australia, thyroid preparations and T3 are prescription-only, so talk to your pharmacist before trying any thyroid blend.

If you have been browsing "thyroid support", "glandular" or "T3" products online, here is what they can contain, why it matters if you already take thyroid medication, and how to read a label before you buy.

When to get help straight away

Most signs of too much thyroid hormone are reasons to see your GP, but some need help fast. Call 000 for chest pain that is severe, getting worse or has lasted 10 minutes, or for a racing heartbeat. healthdirect lists both as reasons to call an ambulance.

If you feel shaky, hot and sweaty, wired or unable to sleep after starting a thyroid product, see your GP the same day and take the pack with you. Always tell an emergency team about every supplement you take: in one published case, knowing about a cow thyroid supplement changed how a person's irregular heart rhythm was managed.

What is a thyroid glandular supplement?

A glandular supplement is made from an animal organ that has been dried and powdered. A thyroid glandular usually comes from cow (bovine) or pig (porcine) thyroid and may be labelled thyroid, thyroid powder, thyroid tissue, thyroid concentrate or raw thyroid. They are mostly sold online, often with promises about metabolism, energy or "natural" thyroid support.

The thyroid gland is where the body makes and stores thyroid hormone, so dried thyroid can carry real T4 and T3. In the 1980s, more than a hundred people in the US Midwest developed thyrotoxicosis, meaning their thyroid hormone levels ran too high, after eating minced beef that had been accidentally contaminated with cattle thyroid during processing. The outbreak ended when that processing step stopped. In 1989, US doctors described a "health-food" cow thyroid product that could cause either an overactive state or a return of underactive symptoms, because its hormone content was unknown and unstandardised.

What testing has found inside "thyroid support" products

Testing of these products is limited and all from the United States, but the findings point the same way.

• Thyroid support supplements: a 2013 study tested ten supplements sold for thyroid support. Nine contained T3 and five contained T4. Taken as directed, half of them delivered more than 10 micrograms of T3 a day, and the authors noted that some exceeded common treatment doses for an underactive thyroid.
• Glandular products: scientists at the US Food and Drug Administration bought 58 thyroid-related products online between 2017 and 2018. Eleven of the 19 glandular products contained measurable thyroid hormone, up to about 210 micrograms of T4 and 32 micrograms of T3 in a day's serving.
• Products without glandular tissue: some labelled as plant extracts, vitamins or minerals contained large amounts of T2, a related compound. The study measured the amounts, not their effects.

Not every supplement is affected: a separate US analysis found negligible thyroid hormone in weight-loss products. The concern sits mainly with products containing thyroid tissue or sold on a thyroid promise. We could not find any published testing of products sold in Australia.

Why it matters if you take levothyroxine

Levothyroxine is a measured dose of T4, adjusted against your thyroid results until it sits where your doctor wants it. A glandular or hormone-containing supplement adds an extra dose on top that nobody is measuring, and the amount can vary from product to product.

Too much thyroid hormone tends to feel like being revved up: a fast or pounding heartbeat, shakiness, feeling hot and sweaty, anxiety, poor sleep, diarrhoea and weight loss. Our guide to levothyroxine side effects and signs your dose is too high or too low goes through the full list.

Case reports show how this plays out. In one, a person developed atrial fibrillation, an irregular heart rhythm, after taking a cow thyroid supplement bought over the counter. In another, a health-food thyroid product taken in place of thyroxine produced erratic test results. Over the longer term, the American Thyroid Association names atrial fibrillation and thinning bones (osteoporosis) as the main harms of too much thyroid hormone, especially in older people and after menopause. That is why your doctor aims for a target range rather than "more is better".

Extra hormone can also make your results harder to read:

• T3 moves fast. A computer model built from the measured contents of US supplements predicted that some held enough T3 to cause an overactive state, in some cases while TSH still read normal or low-normal.
• Mixed signals. With hormone coming from two sources, it is hard to tell whether your prescribed dose is right. US specialists have reported confusion interpreting thyroid tests in people taking thyroid extract.
• After thyroid cancer. Case reports describe prescribed pig thyroid extract raising thyroglobulin, the marker used to watch for the cancer returning, which settled once it was no longer taken.
• Biotin. Common in hair and "energy" blends, it can make some thyroid tests read wrongly. See our guide to biotin and thyroid test results.

"T3 supplements" versus prescription T3 and desiccated thyroid

Searches for a T3 supplement often mix up three quite different things.

• Prescription T3 (liothyronine). In Australia, T3 is a registered prescription medicine, liothyronine, sold as Tertroxin. It is on the PBS with an authority for an underactive thyroid and for thyroid cancer, and its own prescribing information says thyroxine is normally the medicine of choice for routine replacement. Whether it suits you is a conversation for your doctor.
• Desiccated thyroid extract. This is dried pig thyroid made as a prescription preparation. Writing in the Medical Journal of Australia in 2016, an Australian endocrinologist noted that it is not approved by the TGA or listed on the PBS, and is not considered standard therapy. The American Thyroid Association recommends levothyroxine in preference to thyroid extracts, citing concerns such as T3 levels above the normal range, and a 2024 review found the two randomised trials comparing them showed no difference in quality of life or symptoms.
• Over-the-counter "thyroid" or "T3" products. These are supplements, not medicines with a set, checked hormone dose. Some contain glandular tissue. Others contain herbs, minerals or related compounds such as T2.

If you feel your current treatment isn't working, that is a real conversation to have with your doctor. A product that may or may not contain hormone is not a safe way to test the question.

If a product contains thyroid tissue, it may contain thyroid hormone. On levothyroxine, that is a dose nobody is measuring.

How are thyroid supplements regulated in Australia?

In Australia, thyroid preparations, liothyronine (T3) and thyroxine (T4) all sit in Schedule 4 of the national Poisons Standard, the prescription-only schedule. Complementary medicines with an AUST L number may only contain pre-approved low-risk ingredients, and the TGA says an ingredient in a Poisons Standard schedule is one reason a medicine must be registered and fully evaluated instead. So a product that genuinely contained thyroid tissue or hormone would be a prescription medicine here, not an everyday supplement.

Products bought from overseas websites are a different story. The TGA says most medicines containing animal material cannot be imported for personal use, and warns that medicines sold online may have undeclared ingredients, a different dose to the one advertised, or none of the advertised ingredient at all. The largest US analysis above tested products bought online.

Other thyroid-blend ingredients to check with a pharmacist

Thyroid blends often combine several ingredients. Three deserve a closer look if you take thyroid medication:

• Kelp, seaweed or iodine. The American Thyroid Association cautions against high-dose iodine for people whose thyroid gland is already affected by a thyroid condition. Our guide to why more iodine isn't better explains why.
• Ashwagandha (withania). It may shift thyroid hormone levels, and the TGA has published safety information about a very rare risk of liver injury. Read more in ashwagandha and levothyroxine.
• Tyrosine. An amino acid the body uses to make thyroid hormone. US endocrinology guidance notes there are no published data showing that taking it increases thyroid hormone production.

How to read a label before you buy

Read the full ingredient list, not just the front of the pack. Words worth asking a pharmacist about include:

• thyroid, thyroid powder, thyroid tissue, thyroid concentrate, thyroid glandular or raw thyroid
• bovine or porcine thyroid, or a "glandular blend" or "multi-glandular"
• T3, T4, triiodothyronine, thyroxine, T2 or diiodothyronine
• kelp, seaweed or iodine, ashwagandha or withania, tyrosine, and biotin

Be wary of any product that promises to reduce or replace your thyroid medication. On a capsule or tablet sold as a medicine in Australia, look for an AUST L or AUST R number, which shows it is entered on the TGA's register.

Then take the pack, or a photo of the ingredient list, to your pharmacist, and tell your doctor about everything you take, including supplements bought without a prescription. If your pharmacist is happy for you to take a product, ask how to time it around your tablet, because many supplements need to be kept several hours apart from levothyroxine. Our guide to timing supplements around levothyroxine has the detail. For a wider checklist, see what to look for in a thyroid supplement in Australia.

Where ThyroBase fits

ThyroBase is a daily morning and evening plant-based drink powder, a food rather than a medicine, made in Australia. It contains no thyroid tissue, no glandulars, no added thyroid hormone, no added iodine, no added biotin and no ashwagandha. It sits alongside your thyroid medication, never instead of it, and because both serves contain minerals, keep them several hours away from your tablet. Here is who ThyroBase is, and is not, designed for.

Frequently asked questions

Do thyroid glandular supplements contain thyroid hormone?

They can. Glandulars are made from dried animal thyroid, and an analysis by US Food and Drug Administration scientists found measurable T4 or T3 in 11 of 19 glandular products bought online. The amount isn't stated on the label and can vary, so there is no way to know what dose you are getting.

Can I take a thyroid support supplement with levothyroxine?

Check with your pharmacist or doctor first, and bring the label. Products containing thyroid tissue or hormone add an unmeasured dose on top of your tablet, and ingredients such as kelp, ashwagandha and biotin can shift your levels or your test results. Many supplements also need to be kept several hours away from levothyroxine.

Can you buy a T3 supplement over the counter in Australia?

No. Liothyronine (T3) is in Schedule 4 of the Poisons Standard, which makes it a prescription-only medicine in Australia. Products marketed online as "T3" or "thyroid support" are supplements rather than T3 medicine, and some tested overseas have contained hormone or animal thyroid that was not declared on the label.

Is desiccated thyroid the same as a glandular supplement?

Both come from dried animal thyroid, but desiccated thyroid extract is a prescription preparation, while glandular supplements are not sold with a checked hormone dose. An Australian endocrinologist noted in 2016 that it was not TGA-approved or on the PBS and is not standard therapy here, and the American Thyroid Association recommends levothyroxine in preference to it.

What should I do if I have been taking a glandular and feel unwell?

See your GP the same day if you feel shaky, hot, sweaty or wired, or notice a pounding heart, and take the product with you. Call 000 for chest pain or a racing heartbeat. Don't adjust your levothyroxine yourself; a thyroid test will show where your levels are, and your doctor can take it from there.

The honest takeaway

Thyroid glandulars and "T3" products are not simply stronger vitamins. Made from thyroid tissue, or sometimes carrying undeclared hormone, they can add a dose nobody is measuring on top of the one your doctor has set. US testing has found real hormone in most thyroid support products tested, and in Australia thyroid preparations and T3 are prescription-only for good reason. Read the full label, ask your pharmacist before you buy, and tell your doctor about everything you take.

ThyroBase is a nutritional supplement and is not intended to diagnose, treat, cure, or prevent any disease. It is designed to sit alongside your thyroid medication, not replace it. This article is general information, not medical advice. Never start, stop or change a supplement or prescription medication without speaking to your doctor or pharmacist first.

References

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