GLP1 Cold: Feeling Cold or Catching a Cold on GLP-1 Medicines (October 2026)

01 · The core answer

Is feeling cold a GLP-1 side effect?

Feeling cold is not a listed side effect of Mounjaro (tirzepatide) in the UK patient leaflet.¹³

Mounjaro works by activating two gut-hormone receptors, GIP and GLP-1, which helps regulate appetite and slows how quickly the stomach empties.¹ Most people feel fuller sooner and less hungry between meals. That is the documented action. Feeling cold is not part of that description.

02 · Which one do you mean?

Feeling cold or catching a cold: which applies to you?

The two situations call for different next steps, so it helps to sort out which one you are dealing with before doing anything else.

Your prescriber knows your history and the other medicines you take, so they are the right person to interpret a new symptom.

03 · Your next step

What to do if you feel cold on treatment

Start by writing down what you notice, because a clear note makes a consultation far more useful. Record when the feeling began, whether it follows your injection day, whether you changed dose recently, and any other symptoms. A tracking tool such as the free GLPTrackr app can hold these notes alongside your injection log.

Then contact your prescribing team. Our aftercare includes ongoing monthly reviews, dose-titration and follow-up assessments, plus side-effect support, so a new symptom has a proper place to go. If you are new to treatment, our weight loss clinic page explains how reviews work.

Do not change or skip doses on your own because of a symptom. Any change to your dose should be agreed with your prescriber. If you want a longer read on how readers describe the experience, our guides on feeling cold on Mounjaro and whether Mounjaro makes you cold go through the same question with Mounjaro specifically.

04 · Why we avoid guessing

What can cause feeling cold

Feeling cold is not listed as a side effect in the UK patient leaflet.¹³ That does not mean you imagined it, and it does not mean you should ignore it.

Feeling cold has many everyday causes that have nothing to do with a prescription. Changes in what and how much you eat, a cool room, poor sleep, illness, stress and other medicines can all play a part. Some medical conditions can also make people feel the cold more. Sorting these apart is a job for a clinician who can ask you questions, so speak to your prescriber.

If you want to read more around the topic, our pages on freezing cold on Mounjaro and Mounjaro making you feel cold cover the same ground from a different angle.

05 · Catching a cold on treatment

Can you take Mounjaro with a cold?

Whether to inject during a viral cold is a question for your prescriber.

Tell your prescribing team the symptoms you have, when they began, and whether you are eating and drinking normally. If a cold leaves you unable to keep fluids down, contact your clinical team — dehydration needs medical help straight away. Your prescriber can tell you whether to take your next dose as planned or whether something else is more appropriate.

Tirzepatide is a once-weekly injection, so the decision usually comes up only once in any given week. That gives you time to ask rather than guess. Contact the team before your usual injection day, not after.

Mounjaro slows how quickly the stomach empties.¹ If a cold or any illness makes you feel unwell in your stomach, that is another reason to mention it. Do not push through a dose out of habit if you feel poorly. Check first.

06 · Cold and flu remedies

Can you take cold medicine on a GLP-1 medicine?

Check with a pharmacist before taking cold remedies, because combination products contain several active ingredients. Combination products contain several active ingredients, and each one needs checking against your own health history and other medicines.

When you ask, say three things: that you use a once-weekly tirzepatide injection, which other medicines you take, and what symptoms you want to treat. Take the leaflet or your prescription details if you have them.

If a remedy you are considering is not covered by anything you have been told, ask first.

Simple supportive measures, such as rest and keeping up your fluids, are something you can discuss with your prescriber too. If symptoms are severe, last longer than you would expect, or you are worried, speak to your GP or NHS 111 as you normally would.

07 · How long side effects last

How long do Mounjaro side effects last?

Side effects are most likely when starting treatment or moving up a dose, and for most people they ease within days to a few weeks as the body adjusts.

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.¹ There is no way to speed this up, and nothing needs doing while it clears.

If a symptom persists, gets worse or worries you, tell your prescriber. They may look at your dose, your diet, your other medicines and your general health. You can also report a suspected side effect, even one that is not listed, through the MHRA Yellow Card scheme.¹⁹

Our broader guide to feeling cold while on Mounjaro also lists questions to take to an appointment.

08 · Cold and weight loss

Does feeling cold mean I am losing weight?

No. Feeling cold is not a measure of weight loss, and it is not a sign that treatment is working. The scales, your measurements and your clinical review are better indicators.

What the trials show is average weight change, not how people feel day to day. In the SURMOUNT-1 trial, 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

So please do not take a chilly feeling as proof of progress, and do not read the absence of it as a sign you are doing something wrong.

If you want to talk through realistic expectations, your monthly review is the right place.

09 · Storage and cold chain

Cold chain, delivery and pen storage

"Cold" also comes up around delivery, and this is about the pen, not you. Your Mounjaro pen should be kept in the fridge at 2–8°C until first use, and unopened pens keep until the printed expiry date.¹¹³ Once in use, a UK 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.¹³

We send orders by free next-day tracked delivery with DPD, in temperature-controlled, discreet packaging. Orders placed by 3pm are dispatched the same day. Saturday delivery is £14.99. If you are worried about a parcel that sat outside for a long time, see our guide on Mounjaro delivery and keeping it cold, and contact the pharmacy rather than guess.

For any out-of-fridge question about an unopened pen, read the patient information leaflet and ask the pharmacy.

If you are weighing up whether to start treatment at all, the Mounjaro pen is a once-weekly option and the Wegovy pen is another licensed option. You can read more about the Mounjaro pen. You can also look at the Wegovy pen. A GPhC-registered prescriber reviews every consultation, and the consultation is free.

10 · 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