The most common side effects of weight-loss drugs and how to deal with them

Tanya Reynard | Last update: 10th May 2025

1. Nausea

Nausea is one of the most commonly reported side effects of weight-loss medications, especially GLP-1 inhibitors (these are weight-loss treatments that help you feel full faster and eat less). It usually occurs in the first few weeks as your body adjusts.

How to manage it:

• Start slow: Many medications are started at a low dose and gradually increased to help minimise nausea. Follow your healthcare provider’s guidance on dosing.
• Eat small meals: Eating smaller, more frequent meals can help prevent your stomach from feeling too full, which often triggers nausea.
• Avoid greasy foods: Fatty and fried foods can make nausea worse. Stick to lighter, blander options when you’re feeling off. Go for cold foods rather than hot meals with smells.
• Try ginger: Ginger helps the body process food more quickly through the digestive system meaning it doesn’t linger as long in the gut and so can help with nausea -drink ginger tea or eat ginger chews.

Many SlimrChat members have shared their experiences and how they have dealt with it. Emma shared that ‘In my first week on the medication, I felt queasy almost all the time. I found that keeping some plain crackers and ginger tea nearby helped settle my stomach. After a couple of weeks, that nausea sensation went away and now I rarely experience it.’ 

For a more in-depth look at the nausea side-effect and how to tackle it, click here to see our article, Beating nausea: your simple fixes for the most common GLP-1 side effect.

2. Constipation

Constipation can be another common side effect, as weight-loss medications can slow down digestion. This is more likely if your appetite has decreased significantly and you’re eating less.

How to manage it:

• Stay hydrated: Drinking plenty of water is crucial. Dehydration can make constipation worse.
• Increase fibre gradually: Add more high-fibre foods like vegetables, fruits, and whole grains to your diet. Prunes especially are effective as they contain not only fibre but also sorbitol, a naturally occurring sugar alcohol that has a laxative effect. You could also consider a fibre supplement to your diet.
• Stay active: Light exercise, like walking, can help keep your digestive system moving.
• Respond to your body: when you feel the urge, don’t wait – head to the toilet asap!

For more information click here to see our article, The constipation conundrum: practical solutions for relief.

3. Fatigue

Some users report feeling unusually tired, especially when they first start their weight-loss medication. This is usually due to your body adjusting to changes in appetite and calorie intake.

How to manage it:

• Rest when needed: Listen to your body. It’s okay to take it easy while your body is adjusting.
• Fuel your body: Make sure you’re eating enough, even if your appetite is lower. Focus on nutritious foods that provide energy, such as fruits, vegetables, and lean proteins. Remember, weight-loss treatments work best when supported by a healthy lifestyle.
• Stay active: Gentle exercise can boost your energy levels. A short walk might be just what you need to shake off fatigue.

For a deeper look at the tiredness side-effect and ways to tackle it, click here to our article, Are weight-loss drugs making you feel tired? Here are some tips to get your energy and focus back.

4. Digestive Issues

Other digestive issues like bloating or diarrhoea can also occur as your body adjusts to the medication. These side effects are generally short-lived.

How to manage it:

• Avoid trigger foods: Spicy or fatty foods can sometimes make digestive issues worse. Pay attention to what foods may be triggering symptoms for you.
• Eat slowly: Eating too quickly can cause you to swallow air, which may lead to bloating. Take your time when eating.
• Stay hydrated: Drinking water can help ease digestive discomfort and prevent dehydration if you experience diarrhoea.

If you are suffering from bloating in particular, click here to see our article, Why you might feel bloated — and how to ease the discomfort.

5. Headaches

Headaches can happen for a number of reasons, including dehydration or changes in eating habits. They can be more common in the first few weeks of starting a new weight-loss medication due to the change your body is experiencing.

How to manage it:

• Stay hydrated: Dehydration is a common cause of headaches. Make sure you’re drinking enough water throughout the day.
• Eat regularly: Skipping meals or eating too little can lead to headaches. Even if your appetite is low, try to eat small, nutritious meals at regular intervals.
• Over-the-counter pain relief: If headaches are persistent, consider an over-the-counter pain reliever. However, consult with your healthcare provider before taking any additional medication.

6. Bad Breath

Bad breath is another side effect some people experience, particularly when their body is adjusting to a lower calorie intake or ketosis (a metabolic state where your body burns fat for energy).

How to manage it:

• Stay hydrated: Drinking plenty of water helps flush out ketones (the chemicals the body produces when it converts fat cells into energy and it is these chemicals that have an odor) can improve breath.
• Oral hygiene: Brush your teeth and tongue more frequently, and consider using mouthwash.
• Chew sugar-free gum: This can help stimulate saliva production, which helps keep your mouth fresh.

7. Feeling cold

Some people report feeling colder than usual while on weight-loss medications. This can be due to reduced calorie intake, which can lower your body’s metabolic rate.

How to manage it:

• Dress warmly: Wear layers and keep a blanket handy, especially during colder months.
• Stay active: Light exercise can help boost circulation and warm you up.
• Warm drinks: Drinking warm tea or other hot drinks can help raise your body temperature and make you feel more comfortable.

For more information on side effects and strategies to minimise them click through our articles, 10 Easy tips to overcome side effects when taking GLP-1 weight loss treatments and Choosing your weight loss treatment injection day and time to maximise effectiveness and reduce side effects.

When to seek medical advice

While most side effects are mild and temporary, it’s important to know when to seek medical help. Contact your healthcare provider if:

• Side effects are severe or persistent: If you’re struggling to manage side effects or they aren’t going away after a few weeks.
• You’re experiencing unusual symptoms: Symptoms like severe abdominal pain, dizziness, or signs of an allergic reaction need medical attention.

Remember: Everyone’s journey is different

Not everyone will experience side effects, and if you do, they’re often mild and short-lived. Your body needs time to adjust, and that’s perfectly normal. It’s important to stay patient, listen to your body, and remember why you started this journey in the first place.

Be mindful of when you experience any side effects and what may be triggering them. For instance, some of our members have experienced nausea soon after taking their dosage but it wears off after a few hours and as a result, members suggest taking it easy after taking your dosage. Some members have found that they dehydrate quicker causing headaches, as one of our members, Tom, explained, 

‘I was really worried when I started experiencing headaches in the first few weeks. I felt like giving up, thinking that maybe this just wasn’t for me, but I kept reminding myself that my body was just adjusting. I started keeping a water bottle with me at all times drinking lots, and after a couple of weeks, the headaches were gone. Now I feel better than ever but I do know how dispiriting it can feel.’ 

You aren’t the only person experiencing side effects, so why not ask our community about their experiences and what remedies they have found? Or perhaps you have found a remedy that works for you that you could share to help others? If so, click the button below and join the chat now!