A new class of medications—GLP-1 receptor agonists, commonly referred to as GLP-1s—is taking the market by storm. One compound, semaglutide, accounts for a lot of the news you may have seen. Semaglutide mimics a naturally occurring gut hormone called incretin, naturally released after you have eaten, leading to a decreased feeling of hunger. 

Semaglutide comes in a number of different forms: you may know it by the names Ozempic and Wegovy, which come as a jab taken weekly, or Rybelsus, taken as a daily pill.

Each medication is prescribed for different reasons: Wegovy, is prescribed for patients who are obese or have weight related health issues; Ozempic and Rybelsus are prescribed to lower blood sugar levels in patients with type 2 diabetes. Ozempic and Rybelsus, however, are now also commonly prescribed off-label (e.g. not for their original purpose) for weight loss. 

And while semaglutide has a number of key benefits, as with any medication, Ozempic, Wegovy, and Rybelsus may come with the risk of side effects, ranging from mild to severe. 

Here, we break down the main side effects of Ozempic, Wegovy, and Rybelsus, to help anyone on a course of weight loss treatment fully understand potential outcomes from any of these prescriptions.

Dose titration & side effects

It’s worth starting by noting that side effects are most commonly experienced when you increase the dosage you’re taking, which typically happens once every 4 weeks until you reach the maximum dose.

Dose titration increase for each semaglutide-containing medicine generally follows the below schedule, however some people may choose to remain on lower doses for longer if they are satisfied with their results:

• Ozempic—0.25 mg injection for weeks 1 to 4, increasing to 0.5 mg injection for another four weeks, then increasing to 1 mg [1]. 
• Wegovy— 0.25 mg injection for weeks 1 to 4, increasing to 0.5 mg for weeks 5 to 8, then 1mg for weeks 9 to 12, 1.7mg for weeks 13 to 17, then remaining at 2.4mg (the maximum concentration) from then onwards [2].
• Rybelsus—3 mg tablets for the first 30 days, increasing to 7 mg tablets for at least 30 days, then up to 14 mg from then onwards [3].

Ozempic side effects

Ozempic comes as a four-dose pen, taken once weekly as an injection. 

There are a number of common side effects associated with Ozempic. These include [4]:

• Nausea (felt by 16% of patients in trial)
• Stomach/abdominal pain (7%)
• Constipation (5%)
• Diarrhoea (9%)
• Vomiting (5%)

Nausea, diarrhoea, and vomiting are more likely to happen when you increase the concentration of your Ozempic dosage. There are ways you can go about reducing this. This includes eating more bland food (crackers, rice, toast) and foods that contain more water (soup), avoiding greasy or fried foods, eating more slowly, and avoiding lying down after eating [4].  

If any of the above side effects are persistent speak with a medical professional to understand the best path forward. 

There are also some more serious side effects that can occur as a result of taking Ozempic. These include:

• Low blood sugar (hypoglycemia). Your risk of this will be much higher if you are taking another medication that lowers blood sugar (such as insulin). Signs of hypoglycemia include dizziness, blurred vision, anxiety, irritability, or mood changes
• Kidney problems or kidney failure. Other side effects like diarrhoea and vomiting may cause a loss of fluids, exacerbating any kidney problems. To avoid this, drink plenty of fluids 
• Gallbladder problems. Signs of this include pain in your abdomen, fever, jaundice (where your skin or eyes turn yellow), or clay-coloured stools
• Changes in vision, such as diabetic retinopathy, macular complications, and blurred vision 

The severity of these side effects will vary from each person, but if you do experience any of these you should notify a health professional.

If you experience any of the following side effects, you should stop taking Ozempic immediately:

• Inflammation of the pancreas. You’ll be able to recognise this if you have severe stomach pain, which you can feel from your abdomen to your back.
• Serious allergic reactions. This might include swelling in the face lips, tongue, or throat, breathing or swallowing problems, rashes or itching, fainting, dizziness, or a very rapid heartbeat

It’s worth noting that, in trials with rodents, Ozempic has been known to cause thyroid tumours, including cancer [5]. While it is unknown if it poses the same threat to humans, it is a side effect worth knowing about. It’s really important not to take Ozempic if you or any of your family have ever had Medullary Thyroid Carcinoma (MTC), or an endocrine system condition called Multiple Endocrine Neoplasia syndrome type 2. Signs of this include lumps or swelling in your neck, hoarseness, swallowing problems, or shortness of breath. 

Wegovy side effects

Wegovy comes as a single-use pen, which is taken once weekly as an injection 

There are a number of common side effects associated with Wegovy [6]. Many of these are the same as Ozempic. In trials, patients most commonly reported [7]:

• Nausea (44% of patients)
• Diarrhoea (32%)
• Vomiting (25%)
• Constipation (23%)
• Nasopharyngitis/common cold (22%)
• Headaches (15%)
• Dyspepsia/indigestion (10%)
• Stomach/abdomen pain (10%)
• Upper respiratory tract infection (8%)

It’s worth noting, however, that many patients in the trial above on placebo—that is, not taking Wegovy—also reported side effects. For example, 47.9% of patients on placebo reported gastrointestinal side effects versus 74.2% who were taking Wegovy. Other common side effects may include: fatigue, dizziness, bloating, belching, gas, stomach flu, heartburn, runny nose, sore throat.

Again, these are fairly commonly expected with Wegovy (especially when you first start taking it, and when you increase your dosage) and only need to be reported to a doctor/health provider if they persist and are particularly bothering you. 

There are some more severe side effects associated with Wegovy. In trials, small percentages of patients reported the following:

• Serious gastrointestinal disorders (1.4%)
• Psychiatric disorders (10%)
• Cardiovascular disorders (8%)
• Allergic reactions (7%)
• Injection-site reactions (5%)

Other serious side effects listed by Wegovy include pancreatic inflammation/pancreatitis, gallbladder problems, kidney problems, and change in vision. You should be particularly concerned if you notice: an increase in your resting heart rate (report this to a doctor if you feel your heart pounding for at least several minutes); depression or thoughts of suicide—this is why it’s particularly important to be mindful of your mental condition while taking Wegovy. Report this to a doctor if you notice any mental changes that are new and particularly worrying.

Wegovy also comes with the same risk of possible cancerous thyroid tumours. Similarly you should avoid Wegovy if you or any of your family have ever had MTC or MEN 2.

Rybelsus side effects

Rybelsus comes as a tablet, taken daily. 

There are a number of common side effects from taking Rybelsus [8], similar to those of Ozempic and Wegovy. As well as decreased appetite, these include nausea, diarrhoea, vomiting, stomach/abdominal pain, and constipation. As with Ozempic and Wegovy, these side effects are most common when you first start taking the medication, and when you increase your dosage after the first 30 days. 

Rybelsus can also carry more severe side effects, including:

• Pancreatic inflammation (pancreatitis) 
• Changes in vision
• Low blood sugar (hypoglycemia) 
• Kidney problems
• Serious allergic reactions
• Gallbladder problems 

As with Ozempic and Wegovy, you should take the same precautions to limit these risks, and stop taking Rybelsus if you have pancreatitis or serious allergic reactions to the medication. Rybelsus also carries the same risk of thyroid tumours: so likewise, you should avoid taking it if you or anyone in your family has ever had MTC or MEN 2.  

What to do if side effects worsen?

As with any medication, taking Ozempic, Wegovy, and Rybelsus should be done in a safe and responsible way. This includes paying close attention to any side effects you might be experiencing, and taking necessary precautions to limit the risk it might pose to you. 

If common side effects do persist, you should report them to a doctor or health professional. They are best placed to assess any risk you may experience, and whether it is safe or not for you to continue taking the medication. They may also be able to advise on ways to help reduce these side effects. If you are prescribed Ozempic through Habitual, you’ll get full time patient support via our platform, as well as peer support on Whatsapp. 

In some scenarios, when you suffer more serious side effects like pancreatitis or serious allergic reactions, you should stop taking the medication altogether. Ultimately, the goal is to ensure a longer term healthier weight and more stable blood sugar levels, but it's important to respond appropriately to severe side effects should they occur. If it's not safe for you to stay on the prescription due to side effects, you should seek alternatives to achieving the healthier lifestyle you desire.