Switching Levothyroxine Brands in Australia: Oroxine, Eltroxin and More

In Australia, levothyroxine comes in several brands, and they are not all interchangeable dose-for-dose. Oroxine and Eutroxsig belong to one group with several generic brands. Eltroxin and Levothox belong to another, and they are absorbed slightly differently. Every Australian leaflet says not to switch brands unless your doctor advises it. If your brand does change, many specialist groups suggest a thyroid test about six weeks later, so your doctor can check your dose is still right.

If you have ever picked up your script and found a different box, a different colour tablet or a bottle where you expected a strip, you are not imagining that it matters. Here is how the brands differ, how swapping works at the pharmacy, what the research says, and what to do if your brand changes.

The brands, in two groups

On the Pharmaceutical Benefits Scheme (PBS), each brand of a medicine can carry a letter that tells pharmacists which brands are equivalent. Levothyroxine brands fall into two groups:

• The Oroxine group: Oroxine, Eutroxsig and generic brands including APO-Levothyroxine, Levothyroxine Lup and Levothyroxine Sandoz. These are treated as equivalent to each other.
• The Eltroxin group: Eltroxin and Levothox. These are equivalent to each other, but the PBS says it is not known whether they are equivalent to the Oroxine group.

A few other brands, such as Levoxine and Thyrox, are listed separately in bottles. Brands come and go, so the names on the PBS can change over time.

The difference between the two main groups was measured when Eltroxin was approved in 2014. In a single-dose study of 31 healthy adults, the amount of thyroid hormone absorbed from Eltroxin was about 89% of the amount absorbed from Oroxine. The Therapeutic Goods Administration's assessment explains that Eltroxin is made a different way so it doesn't need refrigerating, and that the trade-off is slightly lower absorption.

That does not mean Eltroxin "has less in it". The tablets contain the dose on the label. It means the same dose may be absorbed a little differently, which is why the two groups are not swapped as equivalents.

"Generics are weaker" isn't true

This is one of the most repeated claims in thyroid groups, and the evidence points the other way. The generic brands in the Oroxine group are listed on the PBS as equivalent to Oroxine and Eutroxsig, and some of their leaflets state they are bioequivalent to Oroxine. The group with lower measured absorption is the Eltroxin group, and Eltroxin is made by the same company as Oroxine.

So the useful question isn't "brand or generic?". It is "has my brand changed?", because any change is worth a check.

Fridge or cupboard? Storage is different

This is the uniquely Australian part. According to their current leaflets:

• Oroxine and Eutroxsig are stored in the fridge (2°C to 8°C), in their original blister strips. One strip can be taken out and kept below 25°C for up to 14 days, then any tablets left in it are thrown away. Webster packs are allowed for 14 days below 25°C too.
• Every other brand, including Eltroxin and the generic brands that match Oroxine, is stored below 25°C.

You may have heard that Oroxine must never leave the fridge. The leaflet itself allows one strip out for up to two weeks. The fridge rule dates from 2004, when stability testing found these tablets could lose up to 10% of their thyroxine in the first six months if kept below 25°C rather than refrigerated. Always check the storage line on your own leaflet, because it depends on the brand.

The leaflets also say not to take a tablet if its colour has changed.

How brand swapping works at the pharmacy

Pharmacists can swap between brands in the same group, but only after talking with you, and not if your doctor has ticked "brand substitution not permitted" on your script. Brands in different groups are not swapped as equivalents.

The Endocrine Society of Australia advises that people should not be switched between Oroxine or Eutroxsig and Eltroxin without their own agreement and their doctor's. In practice it still happens. In a 2024 survey of Australian endocrinologists, only 45% said the people they treat were given the brand they recommended.

Brands also look different. Some are white tablets with a number, some are coloured by strength, some come in strips and some in bottles. If your tablets or packet look different from last time, ask your pharmacist before you start them.

What happened when whole countries switched

When large numbers of people have been moved to a new brand or formulation at once, the results have been mixed:

• New Zealand, 2007 to 2008. When Eltroxin was reformulated, New Zealand's medicines regulator told doctors to monitor people, after reports showed raised TSH in some of them. A study later found that symptom reports jumped after television coverage, mostly for the symptoms the TV stories mentioned.
• The Netherlands, 2016 to 2017. A shortage forced about 350,000 people to switch. Among those on more than 100 micrograms a day, 53% showed signs of having too much thyroid hormone.
• France, 2017. A formulation change (lactose swapped for another ingredient) led to more than 17,000 reports of side effects. Where TSH was reported, about 60% were in range, around 20% suggested too little thyroid hormone and about 15% too much.

On the other side, a large US study of nearly 2,800 matched pairs found that switching between generic brands made no meaningful difference to how many people had a TSH in range. Most people who change brand see little or no change in their results. Some do, and you cannot tell in advance which group you are in. The risk may be greater for people with little or no thyroid of their own, and for people after thyroid cancer whose TSH target has been set deliberately.

The UK's medicines regulator also notes that some people report new symptoms after a switch even when their tests are in range. If that happens to you, it deserves a conversation with your doctor, not dismissal.

If your brand changes: about six weeks, then a test

The Endocrine Society of Australia advises a thyroid test about six weeks after a switch between Oroxine or Eutroxsig and Eltroxin. European and US thyroid societies give the same six-week advice for any brand change, and the American Thyroid Association says TSH should be rechecked once levels have settled. Your doctor will tell you when to test, and only your doctor should change your dose.

Shortages can force a switch

Levothyroxine brands do go into shortage in Australia, and some are discontinued. When your usual brand isn't available, that is exactly the time to involve your doctor rather than simply accepting a different box. If you were on a brand in the Eltroxin group, its equivalent is Eltroxin or Levothox, not Oroxine. You can check current supply on the TGA's Medicine Shortage Reports Database.

Ingredients differ too

The active ingredient is the same, but the other ingredients are not. Oroxine, Eutroxsig and several generics contain lactose. Eltroxin's leaflet says it contains no lactose. Some brands use colourings to mark each strength. If you have an allergy or intolerance, the full ingredient list is in your leaflet, so talk to your doctor and pharmacist about which brand suits you.

Your timing doesn't change with the brand

Every Australian levothyroxine leaflet gives the same instructions: take your tablet at least 30 minutes, and preferably 60 minutes, before food or other medicines, and keep calcium, iron and magnesium supplements several hours apart from it. A new brand doesn't change those rules. Our guide to coffee and levothyroxine covers the morning timing in more detail.

What to do

1. Know your brand name and strength, and write them down.
2. Check the box every time you pick up a script.
3. If the brand is different, ask the pharmacist before you start it.
4. If you want to stay on one brand, ask your doctor about marking your script "brand substitution not permitted".
5. Don't take two different brands together to make up your dose.
6. If your brand does change, ask your doctor when to have a thyroid test. About six weeks is common.
7. Never change your dose yourself after a switch. Our guide to how long a dose change takes explains why results need time to settle.

Know your brand. Check the box. Ask before you start a different one.

Frequently asked questions

Are all levothyroxine brands the same in Australia?

No. The active ingredient is the same, but the brands fall into two groups on the PBS. Oroxine, Eutroxsig and several generics are treated as equivalent. Eltroxin and Levothox form a second group that is absorbed slightly differently. Every leaflet says not to switch brands unless your doctor advises it.

Is Eltroxin the same as Oroxine?

Not dose-for-dose. In the study used for its approval, the amount of hormone absorbed from Eltroxin was about 89% of that from Oroxine. Eltroxin is kept below 25°C, while Oroxine is refrigerated. A switch between them should only happen with your doctor's agreement, with a thyroid test about six weeks later.

Does Oroxine have to be kept in the fridge?

Yes. Oroxine and Eutroxsig are stored at 2°C to 8°C in their original blister strips. The leaflet allows one strip to be kept out below 25°C for up to 14 days. Other brands, including Eltroxin and the generics, are stored below 25°C. Check the storage line on your own leaflet.

Are generic levothyroxine brands weaker?

No. The generic brands in the Oroxine group are listed on the PBS as equivalent to Oroxine and Eutroxsig. The brands with lower measured absorption are Eltroxin and Levothox. Any brand change is still worth discussing with your doctor and pharmacist.

How long after changing levothyroxine brand should I have a thyroid test?

Many specialist groups, including the Endocrine Society of Australia, suggest a thyroid test about six weeks after a brand change. Your doctor will tell you when to test and whether your dose needs changing. Never change your dose yourself.

The honest takeaway

Most people who change levothyroxine brand notice little difference, but some see their results move, and Australia's brands are not all interchangeable dose-for-dose. Know your brand, check every box, ask before you start a different one, and if a switch happens, ask your doctor about a thyroid test about six weeks later.

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

healthdirect Australia. Thyroid medicines. healthdirect.gov.au. 2025.
Oroxine (levothyroxine sodium) Consumer Medicine Information and Product Information. Australian Commission on Safety and Quality in Health Care, Medicine Finder. 2025.
Eltroxin (levothyroxine sodium) Consumer Medicine Information and Product Information. Australian Commission on Safety and Quality in Health Care, Medicine Finder. 2024-2025.
Pharmaceutical Benefits Scheme. Levothyroxine listings and Explanatory Notes: symbols used in the Schedule. pbs.gov.au. Accessed October 2026.
Therapeutic Goods Administration. Australian Public Assessment Report for thyroxine sodium (Eltroxin). June 2014.
Endocrine Society of Australia. Statement on thyroxine preparations available in Australia. endocrinesociety.org.au.
Stockigt JR. Should thyroxine tablets be refrigerated? Have we got it wrong in Australia? Medical Journal of Australia. 2005;182(12):650, with author reply.
Lafontaine N, Brown SJ, Perros P, et al. Use of thyroid hormones in hypothyroid and euthyroid patients: a survey of members of the Endocrine Society of Australia. Clinical Endocrinology. 2024;100(5):477-85.
Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: prepared by the American Thyroid Association task force on thyroid hormone replacement. Thyroid. 2014;24(12):1670-751.
Centanni M, Duntas L, Feldt-Rasmussen U, et al. ETA guidelines for the use of levothyroxine sodium preparations in monotherapy to optimize the treatment of hypothyroidism. European Thyroid Journal. 2025;14(4):e250123.
Fliers E, Demeneix B, Bhaseen A, Brix TH. European Thyroid Association (ETA) and Thyroid Federation International (TFI) joint position statement on the interchangeability of levothyroxine products in EU countries. European Thyroid Journal. 2018;7(5):238-42.
Brito JP, Deng Y, Ross JS, et al. Association between generic-to-generic levothyroxine switching and thyrotropin levels among US adults. JAMA Internal Medicine. 2022;182(4):418-25.
Faasse K, Gamble G, Cundy T, Petrie KJ. Impact of television coverage on the number and type of symptoms reported during a health scare: a retrospective pre-post observational study. BMJ Open. 2012;2(4):e001607.
Carswell JM, Gordon JH, Popovsky E, et al. Generic and brand-name L-thyroxine are not bioequivalent for children with severe congenital hypothyroidism. Journal of Clinical Endocrinology and Metabolism. 2013;98(2):610-7.
Medsafe. Eltroxin formulation change: monitor patients and adjust dosing if necessary. 2008.
Medicines and Healthcare products Regulatory Agency. Levothyroxine: new prescribing advice for patients who experience symptoms on switching between different levothyroxine products. Drug Safety Update. 2021.
Therapeutic Goods Administration. Medicine Shortage Reports Database. tga.gov.au.