Jump to: What is Mounjaro, and how does it work? | Nausea and vomiting | Constipation and diarrhoea | Rare side effects | Take home message
The most common side effects of Mounjaro (tirzepatide) are nausea, constipation, vomiting, and other symptoms affecting the gastrointestinal (GI) tract, like diarrhoea. Other common Mounjaro side effects are tiredness, stomach ache, and hedaches.
Side effects of Mounjar typically occur around the time of the injection and during dose escalation. They’re typically transient and will ease after you’ve adapted to the medication.
However, everyone responds differently to these medications; some people won’t experience any side effects, while others will have to discontinue their medication due to the discomfort the side effects cause.
Previous research on GLP-1 medications has suggested a possible link to rare and more severe side effects such as pancreatitis and thyroid cancer.
However, no research has found a connection between Mounjaro and pancreatitis or thyroid cancer.
What is Mounjaro, and how does it work?
Mounjaro is a dual-action weight-loss injection. It’s a GLP-1 receptor agonist (like Wegovy and Ozempic) that reduces appetite, supports weight loss, and improves blood glucose control.
Mounjaro is also a glucose-dependent insulinotropic polypeptide (GIP) mimetic– GIP is a hormone that supports blood glucose levels and helps our fat cells store more excess energy we might consume in our diets.
So, Mounjaro has a dual function that mimics two hormones in the body that support blood glucose levels and weight loss.
Eli Lilly manufactures Mounjaro; the active ingredient in Mounjaro is tirzepatide.
Keep reading as we dig into the side effects of Mounjaro and how to manage them.
1) Nausea and vomiting
Nausea is the most common side effect of Mounjaro and occurs in 13-25% of individuals on the medication. The incidence is dose-dependent, so the higher the dose, the more likely you will experience nausea.
However, it’s typically transient and eases after the body has adapted to the medication or the higher dose you’ve started.
Vomiting is also common when taking Mounjaro, affecting 5-14% of patients on the medication.
Both of these side effects are mainly attributed to the impact of GLP-1 medications to slow down gastric emptying and cause gut distension (enlargement). GLP-1s also communicate with our nervous system, which can disrupt signalling pathways.
These physiological effects mean food takes much longer to pass through our digestive system.
Nausea and vomiting appear to be most common when people overeat or potentially overeat fat which also slows down gastric emptying and could further worsen symptoms.
Here are some tips to reduce nausea and the risk of vomiting on Mounjaro:
- Eat smaller meals
- Eat slowly and mindfully
- You might need to include snacks in-between your three main meals to ensure you’re eating enough
- Stay hydrated
- Avoid foods that previously made you nauseous
- Record a food diary of foods you notice trigger symptoms
- Eat simple meals based on a good source of protein, complex carbohydrates, fruit or vegetables, and some fat
- Don’t lie down after your meal; maybe opt for a short walk
- Avoid eating too close to bedtime
- Speak to your doctor or prescribing physician if symptoms persist or become too uncomfortable
2) Constipation and diarrhoea
Diarrhoea is the second-most-common side effect of Mounjaro, affecting 8-21% of participants. Constipation is less common, occurring in 6-9%.
Constipation may occur due to reduced muscle contractions in the colon when taking the medication. The causes of diarrhoea on Mounjaro aren’t fully understood.
However, these side effects are typically transient and ease after the body has adapted to the medication or the higher dose you’ve started.
Here are some tips to reduce constipation and diarrhoea on Mounjaro:
- Stay hydrated
- Eat a wide variety of fibre sources (nuts, seeds, fruits, vegetables, legumes)
- Exercise and move regularly
- Go to the toilet when needed (don’t try to hold it in)
- Adopt a proper toilet position and place your feet on a stool to help your bowel movements
- Experiment with probiotics and fermented foods like yoghurt, kimchi, fermented beetroot, or kombucha
- Speak to your doctor or prescribing physician if symptoms persist or become too uncomfortable
3) Rare side effects
Thyroid cancer and thyroid-related disorders
A recent meta-analysis (a study reviewing many studies on one topic) analysed the risk of thyroid cancer (and other thyroid-related conditions) associated with the use of GLP-1 receptor agonists like semaglutide (Wegovy) and liraglutide (Saxenda).
The results indicated that liraglutide (Saxenda) slightly increases the risk of thyroid-related disorders compared to placebo.
This is well-documented in the literature, and individuals with a family history of thyroid cancers and related disorders shouldn’t take liraglutide.
Another GLP-1 dulaglutide was also shown to increase the risk of thyroid cancer and related disorders. It’s essential to note that these are rare side effects, and the overall risk is still minimal.
However, a systematic review and meta-analysis of 10 trials in 6,836 participants reviewed the adverse events and most common side effects of Mounjaro.
There were no reported cases of thyroid cancer, or thyroid-related conditions, related to Mounjaro.
Pancreatitis and pancreatic cancer
Despite the current guidelines against individuals with a history of pancreatic cancer or pre-existing pancreatic conditions, there’s no evidence that Mounjaro increases the risk of pancreatitis or pancreatic cancer.
A systematic review and meta-analysis of 10 trials in 6,836 participants reviewed the adverse events and most common side effects of Mounjaro. There were no reported cases of acute pancreatitis related to Mounjaro.
Still, a potential link between pancreatic function and Mounjaro can’t be completely ruled out. But based on the currently available data, it doesn’t seem to increase the risk of these conditions.
Additionally, using Mounjaro has been shown to significantly improve insulin sensitivity and the ability of pancreatic beta-cells to produce and secrete insulin.
So, it’s likely that the benefits to glucose management and insulin sensitivity observed with Mounjaro outweigh any potential risks associated with pancreatitis for most people.
Fatigue
A systematic review and meta-analysis of 10 trials in 6,836 participants reviewed the adverse events and most common side effects of Mounjaro. There were no reported cases of fatigue related to Mounjaro.
However, researchers conducted exit interviews with patients on Mounjaro to collect qualitative data on their experience.
A few patients reported fatigue, with one saying, ‘I got real slow, like lazy. I don’t know what it was, but I was tired or whatever.’
Online community forums also suggest that fatigue seems to be a side effect people are experiencing.
There are a few possible explanations why Mounjaro may lead to fatigue (important: this is speculation at the moment; research has yet to be conducted to test these theories):
- Mounjaro interacts with an area of the brain called the hypothalamus; this regulates our sleep-wake cycle. The interaction between Mounjaro and the hypothalamus may disrupt the regulation of our sleep-wake cycle, causing fatigue.
- Mounjaro may reduce appetite to such an extent that people don’t consume enough calories; this reduces the energy available to the body for essential functions
Here are our top tips to prevent and manage fatigue on Mounjaro:
- Eat enough in your meals, and include snacks in between if needed
- Ensure a source of protein at each meal
- Aim to eat 5-9 servings of fruit and vegetables a day and cook your vegetables to make them easier to digest
- Stay hydrated
- Exercise and move regularly
- Consider taking a multivitamin
- Get daylight exposure, particularly in the morning
- Aim to sleep 7-9 hours per night
- Avoid caffeine after midday if you’re caffeine-sensitive
- Speak to your doctor or prescribing physician if symptoms persist or become too uncomfortable
Take home message
Mounjaro is generally considered a safe and effective medication for most people living with obesity or type 2 diabetes.
Data from randomised controlled trials suggests that while over 90% of participants will experience side effects at least once, they’re typically mild and transient, resulting in only a small number stopping the medication.
This research shows that over 90% of those who start Mounjaro can continue taking it for over one year, suggesting that the medication is tolerated well and the side effects are manageable.
Additionally, there are practical ways to manage medication-related side effects, which can be easier with the right support.
On Second Nature’s two medication-supported programmes: the Wegovy weight-loss programme and the Mounjaro weight-loss programme, you get access to a registered nutritionist five days a week to help you develop healthy habits and manage side effects naturally.
Why should you choose Second Nature over other medication providers if you’ve decided to try Mounjaro (assuming you’re eligible)?
For peace of mind.
Second Nature has worked with the NHS for over 6 years providing weight-loss programmes across the UK.
While our Wegovy and Mounjaro weight-loss programmes are private and not currently used by the NHS, we’ve built the programmes with a focus on scientific evidence, patient safety, and data security.
We hope that our 6+ years of working with the NHS and building a track record of effective weight-loss results will give you peace of mind to give us a try.
Please note: We generally recommend speaking with your GP/doctor before you start taking any new medication like Mounjaro. If you do sign up for Second Nature's Mounjaro programme, then we'll also send your GP a letter to let them know you've started a medication-supported weight-loss journey.
