Medications for Hypothyroidism

Finding information on thyroid medications can be confusing as pharmaceutical companies are constantly either merging with another pharmaceutical company or taking over another pharmaceutical company.

Medication for hypothyroidism can be manufactured by one company but distributed by another company, which means the name on the package might not be the same as the Patient Information Leaflet (PIL).

Also, when one pharmaceutical company takes over another one, it seems that they can use the original box but put the tablet strip in with a different company name on it.

Also, the PIL information can be confusing, again, because it may not be the same name on the box or the tablet strip.

We try to make things clearer for people but even we get confused a lot of the time!

Some of the Patient Information Leaflets (PIL) have been obtained from the Medicines and Healthcare Products Regulatory Agency (MHRA) and some from the Electronic Medicines Compendium (emc) website. 

For any medications not on our list you can visit these websites to search for the medication PILs.

Adverse Reactions

We are constantly being contacted by people who find themselves ill with various symptoms for seemingly no reason.  However, once they let me know that their levothyroxine brand has been changed, I ask them to check the ingredients. 

Some manufacturers have replaced lactose with mannitol and this can cause various symptoms in people such as nausea, diarrhoea and various pain issues.   

Two other ingredients that appear to cause adverse reactions in some people are acacia powder and anhydrous levothyroxine.

Our recommendation is that you always check the box when you collect your next pack of levothyroxine (or liothyronine) and if it is a different box or a different name on the box, check the ingredients against your last pack, which you can find in the PIL.

If you start to get different symptoms to your normal hypothyroid symptoms, check the ingredients (if you haven’t already) and make a note of them for future reference.

You could ask your pharmacy to swap the tablets but this is very hit and miss.

It is best to make an appointment with your GP to let them know that you have had an adverse reaction from that particular brand and would like them to put a note on your prescription that you should only be given the brand that did not cause adverse reactions.

If the new brand has caused adverse reactions, please fill out an MHRA Yellow Card as this informs the MHRA of any adverse effects in medications.  If they receive a lot about one particular medication, they should investigate.

Absorption of levothyroxine

There are some liquid levothyroxine brands that have less ingredients than tablets but these are generally more expensive.  If you find that you are intolerant/allergic to several of the ingredients, you could ask your GP if they would prescribe a liquid levothyroxine but they may not agree to do this. 

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If you know of a brand of thyroid medication that is not on this list, please let us know by contacting us on info@thyroiduk.org

 Date updated: 06.07.26 (V3.10)

Review date:  22.08.26