Second Nature logo



Ozempic side effects

Robbie Puddick
Written by

Robbie Puddick

Medically reviewed by

Fiona Moncrieff

8 min read
Last updated June 2024

Jump to: Nausea and vomiting | Constipation and diarrhoea | Rare side effects | Take home message

The most common side effects of Ozempic are nausea, constipation, vomiting, and other symptoms affecting the gastrointestinal (GI) tract, like diarrhoea.

These side effects most commonly occur around the time of the injection, during dose escalation, and are 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.

While not cited in the literature, there are also reports of fatigue from taking Ozempic.

The mechanisms underlying this possible link to fatigue aren’t clear, but it could be an indirect effect of the drug lowering appetite and people not eating enough calories.

There are possible links to rare and more severe side effects such as pancreatitis and thyroid cancer. However, this has not yet been shown in the clinical trials for semaglutide.

Check my eligibility

What is Ozempic?

Ozempic is a type 2 diabetes medication that requires a weekly injection with semaglutide as the active ingredient.

Semaglutide is a GLP-1 receptor agonist that helps reduce hunger and appetite, allowing you to eat fewer calories, lose weight, and manage your blood sugar levels.

Ozempic is for individuals living with type 2 diabetes to help manage blood sugar levels. Ozempic also lowers appetite and can help with weight loss.

Ozempic is taken once a week via a self-administered injection.

Not a magic pill

Weight-loss injections are designed as additional tools for healthy lifestyle change and shouldn’t be considered as lifelong medications.

Instead, they should be used to help you kickstart your weight-loss journey whilst you focus on building new, healthy habits.

Consider the use of antidepressants for people living with depression. They’re not designed to cure the condition. Instead, they’re designed to allow room for therapy to treat the condition’s underlying cause.

Mounjaro and Wegovy are similar. These medications can help silence food-related thoughts and also give you a boost of confidence with more immediate weight-loss results.

This helps to buy you the time and headspace to understand why your body may have struggled to lose weight previously, and to build new long-term healthy habits.

The core focus of our medication programmes are to calm down the feeling of food noise, lower your cravings, and to allow you to build healthier habits to keep the weight off for good.

The ultimate goal is to make losing weight feel second nature.

Second Nature’s medication-supported programmes

Second Nature has two medication-supported programmes: a Wegovy weight-loss programme and a Mounjaro weight-loss programme.

If you’ve made the decision to try Wegovy or Mounjaro (assuming you’re eligible), why should you choose Second Nature over other medication providers?

For peace of mind.

Second Nature has worked with the NHS for over 6 years providing weight-loss programmes across the UK.

Whilst 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.

Otherwise, keep reading as we dig into the side effects of Ozempic and how to manage them.

1) Nausea and vomiting

Nausea is the most common side effect of Ozempic, with at least 25% of participants on GLP-1s experiencing it, with some studies showing up to 53% of participants reporting nausea at least once.

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 semaglutide, with studies suggesting anywhere between 8-30% of participants will experience this at least once.

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 leading to nausea.

These physiological effects mean that 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 Ozempic:

  • 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

Constipation occurs in around 25% of participants taking semaglutide. Unlike nausea and vomiting, which are typically more transient, constipation (for those who experience it) appears to be a longer-lasting side effect of Ozempic.

Constipation may occur due to reduced muscle contractions in the colon when taking the medication.

Diarrhoea is also prevalent with Ozempic, with around 30% of participants experiencing this at least once.

It’s typically transient and should decrease as your body adapts to the medication. The causes of diarrhoea on Ozempic aren’t fully understood.

Surprisingly, much of the guidance to help constipation will also help manage and prevent diarrhoea.

Here are some tips to reduce constipation and diarrhoea on Ozempic:

  • Stay hydrated
  • Eat a wide variety of fibre sources (nuts, seeds, fruits, vegetables, legumes)
  • Exercise
  • 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 (Ozempic) and liraglutide (Saxenda).

The results indicated that liraglutide (Saxenda) slightly increases the risk of thyroid-related disorders compared to a placebo.

This connection to the thyroid with liraglutide 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, semaglutide (Ozempic) was shown to have no impact on the risk of thyroid-related disorders.

Despite this, current recommendations are the same as liraglutide and individuals with a history of thyroid disorders aren’t recommended to take semaglutide.

It’s likely that when more data becomes available, we’ll have a clearer picture of whether Ozempic affects thyroid function and the development of thyroid disorders.

Pancreatitis and pancreatic cancer

Despite the current guidelines against individuals with a history of pancreatic cancer or pre-existing pancreatic conditions, there’s no strong evidence that semaglutide, or other GLP-1 medications, increases the risk of pancreatitis, pancreatic cancer or other pancreas-related conditions.

A study analysed data from 100 randomised controlled trials on GLP-1s and found that 72 of those trials showed no difference between the incidence of pancreatic cancer or pancreatitis compared to the control groups.

Another study analysed the available data on randomised controlled trials that investigated the incidence of pancreatic cancer and pancreatitis on semaglutide specifically and showed no effect of semaglutide on pancreatic-related conditions.

Still, a potential link between pancreatic function and semaglutide can’t be completely ruled out. But based on the currently available data, it doesn’t seem to increase the risk of these conditions.

It’s possible that earlier associations between GLP-1s and pancreatic cancer and pancreatitis were confounded by the increased risk of these conditions in the baseline population of people living with type 2 diabetes who are prescribed these medications.

Additionally, using semaglutide 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 semaglutide outweigh any potential risks associated with pancreatic cancer in the long term.


Interestingly, few of the major trials investigating the impact of Ozempic on weight loss and health report fatigue, tiredness, or lethargy as potential side effects.

However, there are widespread reports that fatigue is a very common side effect linked to its use.

One earlier phase 2 trial on higher-dose semaglutide (1.6mg) indicated that around 12% of participants reported fatigue whilst on the medication. But generally, it’s not a side effect reported in the larger phase 3 trials.

Whether this is due to poor reporting or the researcher’s decision that the fatigue isn’t associated directly with the medication is unclear.

It’s likely due to an indirect effect of the medication reducing appetite to a point where people don’t eat enough, and their bodies enter ‘starvation mode’ whereby metabolism effectively grinds to a halt to ensure sufficient energy delivery to vital organs.

Here are our top tips to prevent and manage fatigue on Ozempic:

  • Eat enough in your meals, and include snacks in between meals if needed
  • Ensure a source of protein at each meal
  • Aim to eat 5-9 servings of fruit and vegetables a day
  • Stay hydrated
  • 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

The recent innovations in GLP-1 medications are pretty remarkable and have caused quite a stir in the world of healthcare.

We’re in new territory where obesity and type 2 diabetes medications treat an underlying cause instead of merely treating the symptoms to support better management.

However, these drugs shouldn’t be seen as miracle cures; they’re not designed to be used for life.

They’ve been designed to be taken alongside lifestyle changes that will enable you to eventually come off the medications and maintain your lower weight for the long term.

The harsh reality is that we still don’t know the long-term effects of these medications on our health. There are examples of drugs being withdrawn from the market as more long-term data comes to light.

Lorcaserin was a weight loss drug approved by the Food and Drug Administration (FDA) in the U.S. but was recently withdrawn as data indicated that it increased cancer risk.

The example of lorcaserin is why you must weigh the pros and cons when your doctor prescribes medication or before you purchase it yourself and start treatment. Report any side effects to your healthcare team.

GLP-1s are safe and effective for most people in the short to medium term, but we don’t have long-term data to be sure they’re not causing severe adverse effects elsewhere.

Meal Plan

Maximise your weight loss on Wegovy/Mounjaro with our free 7-day meal plan

Get expert advice from our team of registered dietitians to make losing weight feel easier while on medication. Subscribe to our newsletter to get access today.

I've read and agreed to the Terms of Service & Privacy Policy.

You might also like

Make losing weight feel Second Nature

The first step on your Second Nature journey is to take our health quiz.

Hand holding phone

Write a response

As seen on

The GuardianThe TimesChannel 4The Sunday Telegraph
Evening Standard