Do GLP-1 Medicines Increase Insulin? (October 2026)

01 · The core answer

So, do GLP-1 medicines increase insulin?

GLP-1 medicines do not add insulin to your body the way an insulin injection does. They act on gut-hormone receptors, and for Mounjaro the product information states that this action helps improve the way the body responds to insulin.¹ That is a different thing from simply raising insulin levels.

The question hides several separate ideas. One is whether the medicine changes how much insulin the pancreas releases. Another is whether the body becomes more sensitive to the insulin it already makes. A third is whether the medicine interacts with insulin treatment you are already taking.

Your prescriber and the GLP-1 effect on insulin guide can take you further. On the second, Mounjaro's dual action helps improve the way the body responds to insulin. On the third, the practical position is that doses of insulin or sulfonylureas may need adjusting because of the risk of low blood sugar. It does not mean you must never combine them.

02 · Is this you?

Is this relevant to you?

It is most relevant if you have been told you have insulin resistance, type 2 diabetes or prediabetes, or if you are on diabetes medicines and are considering a weight-loss injection. It is also relevant if you simply read that GLP-1 medicines affect insulin and want to know whether that is a worry.

Mounjaro is licensed in the UK for weight management in adults and for type 2 diabetes.¹ The licence matters. A medicine licensed for diabetes is assessed in that setting. A medicine used for weight management is reviewed against weight-related criteria. The same pen can serve both purposes, but the reason you are prescribed it shapes the monitoring you receive.

If you take insulin, a sulfonylurea or any other diabetes treatment, do not change anything yourself. Speak to the clinician who manages your diabetes. If you are not on diabetes treatment, you should still mention any blood sugar history in your consultation so the prescriber has the full picture.

03 · What to do next

What to do next

A GPhC-registered prescriber reviews each online consultation with us, and it is free with no obligation. If you already know you want to explore treatment, you can see the current Mounjaro pen prices and consultation and the wider weight loss clinic information.

If you are still researching, the guides on how Mounjaro works for insulin resistance and whether Mounjaro increases insulin go into the Mounjaro-specific detail.

04 · GLP-1 and insulin

What GLP-1 is and how it relates to insulin

GLP-1 is a natural gut hormone, and GLP-1 medicines are designed to activate the same receptors it does. The UK product information describes Mounjaro as the first treatment of its kind to activate two natural gut-hormone receptors at once: GIP and GLP-1.¹ Together, these help regulate appetite, slow how quickly the stomach empties, and improve the way the body responds to insulin.¹

People often assume any drug that touches insulin must either add insulin or push the pancreas hard. Neither description is a fair summary of what the product information says for Mounjaro. A more accurate picture is a medicine that works through natural hormone signals, with effects on appetite, digestion speed and insulin response happening together.

If you want more detail, the full leaflet and your prescriber are the right sources, and the GLP-1 effect on insulin page covers related ground.

It also helps to separate the effects. Feeling fuller sooner and less hungry between meals is an appetite effect. Slower stomach emptying is a digestive effect. Improved response to insulin is a metabolic effect. They are linked in the way the medicine works, but you may notice them differently. Most people notice appetite changes first because they are felt directly, whereas changes in insulin response are not something you can feel.

If your question is practical, such as whether you will need to inject anything extra or whether the pen contains insulin, the answer is no. Mounjaro is a once-weekly injectable prescription medicine in a pre-filled multi-dose KwikPen, and its active ingredient is tirzepatide.¹ It is used alongside a reduced-calorie diet and increased physical activity, not instead of them.

05 · Insulin resistance

Insulin response versus insulin resistance

Insulin resistance describes the body responding less well to insulin, and it is a different issue from having too little or too much insulin.

Mounjaro helps improve the way the body responds to insulin, which points toward better insulin response, not worse. If you have noticed a concern online, it is worth raising it with a prescriber rather than relying on forum posts.

Mounjaro is not licensed to treat insulin resistance as a condition in its own right; the licences are for weight management in adults and for type 2 diabetes.¹ Insulin resistance often sits alongside weight-related health problems, so the two topics overlap in practice. But overlap is not the same as a licensed indication.

Many people who ask this question are trying to understand why their weight, hunger and blood sugar seem tied together. That is a reasonable thing to explore with a clinician, who can look at your own results. Online articles tend to generalise. Your history, medicines and test results are what matter for you.

Our longer guides on how Mounjaro works with insulin resistance and whether Mounjaro causes insulin resistance cover the Mounjaro-specific version of this question. If you want practical habits that sit alongside treatment, the guide to Mounjaro and insulin resistance tips is a sensible follow-up.

Reading about insulin resistance cannot confirm whether you have it. If you suspect it, the route is a conversation with your GP or prescriber about appropriate testing, not self-diagnosis from symptoms or from a product page.

06 · Dual action

Why Mounjaro's dual action matters

Mounjaro differs from single-action GLP-1 medicines because it activates both GIP and GLP-1 receptors. The product information states that this dual action distinguishes it from single-action GLP-1 medicines such as semaglutide, sold as Wegovy and Ozempic.¹

It is also important not to turn "different mechanism" into "better for everyone". The description tells you how the medicines differ, not who will do better on which. Both are effective licensed options.

What you can fairly take from this is that the two medicines are not interchangeable in their mechanism, and your prescriber can discuss which fits your health history, preferences and dosing needs. Tolerability and previous experience all feed into the choice.

If you are weighing the two, the product pages show the Wegovy pen and the Mounjaro pen side by side. For Wegovy, availability should be checked at the time of order.

07 · What trials show

What the weight-loss evidence shows

The best-known evidence for Mounjaro in weight management is the SURMOUNT-1 trial, and it is about weight rather than insulin directly. In the SURMOUNT-1 trial of 2,539 adults, 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 A trial average does not predict your own result.

The trial also reported that at 72 weeks, 85% of participants on 5mg, 89% on 10mg and 91% on 15mg had lost at least 5% of their body weight. Half of participants on 10mg and 57% on 15mg lost at least 20% of their body weight.²

As a worked example only, for someone starting at 100 kg, 20.9% is about 21 kg. That is straight arithmetic of the trial average, not a forecast, and it says nothing about how quickly any individual would reach it.

These trial figures are weight outcomes. They are not insulin measurements and do not show an effect on insulin resistance.

For people with type 2 diabetes, there is separate trial evidence, such as the SURPASS-2 comparison of tirzepatide and semaglutide in that population.³ If you have type 2 diabetes, your diabetes clinician is the right person to explain which trial evidence applies to you.

08 · Other medicines

Taking GLP-1 treatment with insulin or other diabetes medicines

If you already use insulin or sulfonylureas, your doses may need adjusting when you start Mounjaro because of the risk of low blood sugar. That is the key practical point, and it is an adjustment, not a ban on combining them.

It follows that anyone on diabetes treatment should not start a weight-loss injection without telling both their diabetes team and the prescriber. A free consultation with us asks about your medicines for exactly this reason, and a GPhC-registered prescriber reviews your answers. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.

There is a separate and often forgotten interaction. Mounjaro can reduce the absorption of oral contraceptives because it slows stomach emptying.⁷ The SmPC advises switching to a non-oral method, or adding a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.¹ If you use the pill, switch to a non-oral method or add a barrier method as described. Do not assume it is irrelevant simply because your question was about insulin.

Anything specific, such as how much to reduce an insulin dose, belongs in a conversation with the person managing your diabetes.

Our related guides on insulin and GLP-1, the GLP-1 and insulin combination and adding GLP-1 to insulin examine the combination question from different angles.

If you notice a new or worrying symptom after starting treatment, tell your prescriber. You can also report suspected side effects through the MHRA Yellow Card scheme.¹⁹ Our team provides monthly reviews, dose-titration support and side-effect support as part of aftercare, and repeat orders re-check suitability, with no auto-shipping.

09 · Which GLP-1

Which GLP-1 is best for insulin resistance?

No licensed medicine is best for everyone; the choice depends on your health, other medicines, tolerance and goals, and your prescriber decides what suits you.

Mounjaro (tirzepatide) is a once-weekly pen with six strengths, 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg, licensed for weight management in adults and for type 2 diabetes.¹ Wegovy (semaglutide) is a once-weekly pen on its own ladder.¹⁸ Liraglutide products such as Saxenda are daily injections supplied at 6mg per millilitre. For anything beyond that, your prescriber can advise.

So the useful questions to ask a prescriber are these. Which licensed medicine suits my health history? How will my other medicines be handled? What dose pathway makes sense, and how often will we review? What should I watch for? These are better questions than "which is best".

Metformin comes up often alongside this topic. Do not stop metformin or any prescribed medicine without advice from the person who prescribed it.

10 · NHS and private

NHS access and private treatment

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.⁴⁶ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

If you have type 2 diabetes, your route may differ, since Mounjaro is licensed for that condition too. Your GP or diabetes clinic can tell you what is available locally. NHS access to Wegovy runs through specialist weight-management services, so ask your GP.

If you choose private treatment, the process is straightforward. You complete a short free online consultation. A GPhC-registered prescriber reviews it. Your medicine is dispensed by our registered pharmacy, with same-day dispatch when ordered by 3pm, and free next-day tracked delivery in temperature-controlled packaging. Saturday delivery is £14.99.

Costs matter, so here is the picture. The price shown is the price paid, and the consultation is free. There are no subscriptions, and Klarna and pay-monthly options are available.

Whichever route you take, always check that a pharmacy is genuinely registered. Ours is GPhC 9012878, and you can verify it on the public register.¹² Be wary of anyone offering to supply without a consultation or prescription, and report suspected fakes through the MHRA.⁷

11 · Serious side effects

Serious side effects: when to get help straight away

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. If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion) — your prescriber may need to adjust those medicines.¹

12 · Stopping and questions

Stopping treatment and what to ask your prescriber

Tirzepatide has a half-life of about five days, so after a final dose it takes roughly four to five weeks to clear the system. There is no way to speed this up, and nothing needs doing while it clears.¹

That is useful context for insulin questions. If you stop, the medicine does not vanish overnight. In SURMOUNT-4, people who stopped tirzepatide after 36 weeks regained on average 14% of body weight over the following year, while those who continued treatment lost a further 5.5% on average. Stopping should always be planned with your prescriber. If you take diabetes medicines, tell your clinician if you plan to stop, because they may need to review your treatment.

Before starting, it helps to bring a short list to your consultation. Your diagnoses, including any insulin resistance, prediabetes or diabetes. Every medicine you take, including insulin, sulfonylureas, tablets and contraception. Any history of low blood sugar. Your goals and what has or has not worked before.

After starting, keep in touch. Our team provides ongoing monthly reviews, dose-titration and follow-up assessments, and side-effect support. The free GLPTrackr companion app can help you record your journey. Support runs Monday to Friday, 9am to 5pm, by email at support@everydaymeds.co.uk, by account portal chat or on 0333 207 0413.

Remember storage and handling basics too. Keep unopened pens in the fridge at 2–8°C until first use, and they keep until the printed expiry date. Once in use, a KwikPen can be kept out of the fridge at a temperature not above 30°C for up to 30 days after first use, and must then be thrown away. Do not use a pen that has been above 30°C or frozen. For anything else, check the patient information leaflet.¹³

If a new symptom worries you, tell your prescriber. You can report suspected side effects through the Yellow Card scheme.¹⁹ This page is information, not a substitute for medical advice. Mounjaro is a prescription-only medicine used alongside a reduced-calorie diet and increased physical activity, and individual results vary. For a related angle on why some people feel treatment loses effect, see our guide to GLP-1 resistance.