Can You Use Mounjaro If You Have Hypothyroidism? (October 2026)

01 · The short answer

Can you use Mounjaro if you have hypothyroidism?

In most cases, yes, subject to prescriber assessment. Mounjaro is licensed for weight management in adults and for type 2 diabetes, and the patient information does not name an underactive thyroid among the reasons to avoid it.¹³ What it does name is allergy to tirzepatide, pregnancy or trying to conceive, and a history of pancreatitis, severe gut disease, diabetic retinopathy or gallbladder problems, where extra care is needed.¹³ Mounjaro must not be used during pregnancy, and it should be stopped at least one month before trying to conceive. If you become pregnant during treatment, stop the medicine and tell your prescriber promptly.

So hypothyroidism alone is not the issue. The decision rests on your whole picture: other conditions, every medicine you take, and how well your thyroid is controlled. A GPhC-registered prescriber reviews that during the consultation.

02 · Your next step

What to do before you start

Be ready to share the following during your consultation. Honest answers let the prescriber decide safely.

• That you have hypothyroidism, and the cause if you know it (for example Hashimoto's).
• Your thyroid medicine, usually levothyroxine, and when you take it each day.
• Whether you or a close relative has had medullary thyroid cancer or MEN 2.
• Any other conditions and medicines, including supplements.

If your thyroid medicine dose has changed recently or you suspect it is not working, speak to your GP or endocrinology team first, because sorting that out before starting a new treatment makes your results easier to interpret.

If you are ready to see whether you are suitable, you can start a free consultation for the Mounjaro pen. For wider options, see our weight loss clinic.

03 · Thyroid cancer warning

The thyroid warning explained

The warning on Mounjaro concerns a rare thyroid cancer, not an underactive gland. In rodent studies tirzepatide caused thyroid C-cell tumours; it is not known whether this applies to humans, and no increase has been shown in human trials.¹

As a precaution, tell your prescriber if you or a close relative have had medullary thyroid cancer or the inherited condition MEN 2. They will weigh this in your assessment. Routine thyroid monitoring is not required for most people.¹³

People often confuse the two situations because both involve the word thyroid. Having Hashimoto's disease or another cause of an underactive thyroid is a separate question from having a personal or family history of those specific cancers. Your prescriber will ask about both.

04 · Levothyroxine and Mounjaro

Taking levothyroxine alongside Mounjaro

Tell your prescriber you take levothyroxine, because Mounjaro changes how the gut works. Tirzepatide activates the GIP and GLP-1 receptors, which help regulate appetite and slow how quickly the stomach empties.²

Levothyroxine is taken by mouth and absorbed through the gut, so people reasonably ask whether slower stomach emptying matters. Because Mounjaro slows stomach emptying, it can affect how quickly some oral medicines are absorbed, particularly when you start treatment or increase the dose; your GP or endocrinologist manages your thyroid dose.¹³

Practical points that are safe to follow:

• Keep taking your thyroid medicine as prescribed unless your GP or specialist tells you otherwise.
• Do not change the dose yourself because you are losing weight.
• Ask your GP whether your thyroid blood tests should be checked after you start treatment or as your weight changes.
• Report new or worsening symptoms to your prescriber.

Our prescribing team offers ongoing monthly reviews, so you can raise any thyroid-related questions as you go through titration.

05 · Weight loss and thyroid

Is weight loss harder with hypothyroidism?

Many people with an underactive thyroid find weight hard to manage, and it is fair to say so.

In SURMOUNT-1, people taking tirzepatide alongside diet and exercise lost on average 15% of their body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.² These are trial averages and individual results vary. Treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.²

Do not assume your result will match or fall short of those averages because of your thyroid. Well-controlled thyroid levels, regular follow-up and realistic expectations are the sensible foundations.

06 · Side effects to watch

Side effects and when to get help

Serious side effects are uncommon but need urgent attention. Seek immediate medical help for severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing.¹³

Severe vomiting or diarrhoea can cause dehydration, so keep fluids up and get medical help straight away if you cannot keep fluids down.¹³ Report suspected side effects through the Yellow Card scheme.¹⁹

Some symptoms of an underactive thyroid, such as tiredness or low mood, can overlap with how you may feel during big changes in weight and routine. Tell your prescriber about any history of depression, and seek help promptly if your mood drops or you have distressing thoughts during treatment.¹⁷ Any new symptom is worth discussing rather than guessing at the cause.

If you have thoughts of harming yourself or ending your life, get help straight away. Call 999 or go to A&E if you are in immediate danger. In England you can call NHS 111 and choose the mental health option, any time. You can also call Samaritans free on 116 123, day or night. Tell your prescriber about any change in your mood while taking Mounjaro.

07 · NHS access

Getting Mounjaro on the NHS with hypothyroidism

Having hypothyroidism does not by itself decide NHS eligibility. Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions).⁴

Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.⁶ Your GP can tell you where you sit locally.

08 · Related conditions

Other questions people ask

A separate page looks at using Mounjaro with hypothyroidism from another angle.

Many people with a thyroid condition also have another one. We have guides for PCOS, endometriosis, IBS and lupus, and the same principle applies to each: full disclosure, then individual prescriber review.