Can You Take Mounjaro With an Underactive Thyroid?

Mounjaro (tirzepatide) is a prescription-only, once-weekly injectable medicine that acts on both GIP and GLP-1 receptors to help regulate appetite and blood sugar. When it comes to thyroid health, there are two distinct considerations worth understanding.

The thyroid tumour signal in animal studies

In pre-clinical studies, tirzepatide and related GLP-1 receptor agonists were associated with thyroid C-cell tumours in rodents. It is not known whether this risk applies to humans, but as a precaution, these medicines are generally not recommended for people with a personal or family history of medullary thyroid carcinoma (MTC) or a condition called Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Your prescriber will have assessed this before issuing your prescription. If you have any concerns about your thyroid history, raise them directly with your healthcare professional — this is not a decision to make on your own.

Hypothyroidism (underactive thyroid) specifically

Having a diagnosed underactive thyroid — where the thyroid gland does not produce enough hormone — is a different matter from the C-cell concerns above. Many people living with hypothyroidism are also prescribed tirzepatide, and the two conditions can coexist. However, there are important nuances:

• Thyroid hormone levels and weight: Hypothyroidism can independently affect weight and metabolism, which means your prescriber may monitor thyroid function more closely during treatment.
• Thyroxine (levothyroxine) interaction: If you take thyroxine to manage your hypothyroidism, slower gastric emptying — a commonly reported effect of GLP-1 medicines — may affect how your body absorbs oral medicines. For detail on this, see taking Mounjaro alongside thyroxine.
• Symptoms can overlap: Fatigue, constipation, and feeling cold are reported with both hypothyroidism and as side effects of tirzepatide. Your healthcare team can help distinguish what is driving any new or worsening symptoms.

For broader context on how tirzepatide works in the body, the overview of how Mounjaro works covers the mechanism in plain language. If you are also managing other health conditions, you may find the pages on Mounjaro and gallstones and taking Mounjaro alongside statins useful for context.

According to NHS guidance, people with thyroid disorders should discuss their full medical history with their prescriber before starting any new prescription medicine.

When you are managing hypothyroidism alongside a Mounjaro prescription, keeping a clear record of how you feel day to day becomes especially valuable — not because an app replaces clinical oversight, but because good notes make better conversations with your healthcare team.

GLP Trackr's side-effect and symptom tracker lets you log how you are feeling each day, including fatigue, digestive changes, mood, and energy levels. Over time, patterns can emerge in your own data that are worth discussing with your prescriber — for example, whether certain symptoms cluster around dose days or appear to be unrelated to your injection schedule. This kind of log can be genuinely useful at review appointments, particularly when overlapping conditions make it harder to attribute any single symptom to one cause.

The app's morning check-in captures weight, energy, mood, and sleep in around 30 seconds, giving you a running record without the effort of manual journalling. And if you want to share a structured summary at your next appointment, the doctor report feature pulls your tracked data into a clear overview your prescriber can review.

Important: GLP Trackr is a tracking tool, not a medical service. Any concern about your thyroid function, your symptoms, or your suitability for this medicine should be discussed with your prescriber or doctor — they know your full history. If you notice symptoms that feel severe, sudden, or worrying, contact a healthcare professional promptly rather than logging and waiting.

Log your symptoms, spot your patterns, and arrive at every appointment with clarity. GLP Trackr is free to try for 7 days — available on the App Store and Google Play.