How to manage weight loss injections side effects

Common side effects of weight loss injections

As your body adjusts to the medication and often with increases in dosage, you can experience weight loss injection side effects. While most of the common side effects can be uncomfortable, they often do go away on their own. 

The following is not a complete list. Read the PIL for full safety information and seek urgent care for severe symptoms.

Some patients have found that eating bland meals and smaller meals has helped in reducing the initial GLP-1 side effects they have.

Nausea and vomiting

GLP-1 medications slow down the rate of food leaving the stomach, leading to the stomach producing more stomach acid. This also increases the frequency rate of the stomach churning, all to help digest the food and get it out of the stomach. 

While these weight loss injection side effects often present when the dosage increases, they are ways to manage them:

• Eat smaller meals to reduce any strain on the stomach

• Chew food thoroughly to slow down eating speed and stop as you start to feel full

• Avoid high fat, sugar and spicy food, as this can make symptoms worse

• Drink plenty of fluid to stay hydrated and help the digestive system stay regular

If you find that your symptoms are persistent, we have nausea and sickness relief options. However, if your symptoms are more severe, speak to your doctor for additional support and advice.

Digestive issues

Additional side effects that affect the digestive symptom include constipation, diarrhoea or bloating that are caused through digestive mobility. Where the digestive system is moving at a different pace than normal. 

GLP-1 medication typically slows the rate of food leaving the stomach but how much fluid we drink and the body retains can impact digestive mobility beyond the stomach. 

• Stay hydrated, even if you experience diarrhoea, as it helps with nutrient absorption and affects the consistency of your stools

• Eat balanced meals that have fibre rich foods (recommended 30g per day) to help reduce constipation

• Avoid high fat and high sugar meals as they can make symptoms worse

• Light exercise such as walking can stimulate the intestines to move food through the digestive tract

If you're still having GLP-1 side effects that haven't quite gone, we have constipation relief, diarrhoea relief including replacing electrolytes and probiotics to help you support your gut health.

Seek medical advice if you have severe abdominal pain, persistent vomiting, black/tarry stools, or signs of dehydration.

Fatigue

This is more common in the early stages of treatment, as your calorie intake has reduced and your blood sugars have changed as a result. Fatigue isn't a symptom but often a combination of different side effects, such as tiredness, vomiting, nausea and diarrhoea can increase this feeling. 

As you adjust to the medication and your smaller appetite, this feeling will reduce. What you can do to reduce the fatigue:

• Eat smaller meals that are high in nutrients to maintain energy

• Reduce high sugar foods as they cause energy spikes and crashes

• Stay hydrated and rest when needed

• Create a good sleeping routine that's relaxing with no screen and a routine or good quality sleep

• Do gentle movement like yoga and small walks to keep the body moving

For symptoms that need a little support, see our health and wellbeing section. If you find your symptoms are prolonging, please speak to your doctor.

Headache and dry mouth

These weight loss injection side effects are often caused by dehydration, changes in the blood sugar and sometimes, your body adjusting to the medication. 

If you find your fluids have reduced due to other symptoms such as vomiting, nausea or feeling fuller, this can contribute to the side effects. To reduce these side effects:

• Drink water throughout the day, even if it's small sips

• Avoid caffeine or alcohol, which can make dehydration worse

• Suck on ice, ice lollies or sugar free sweets to ease the dry mouth 

If your headache continues, we’ve got treatments that can ease your pain. If you’re looking for ways to keep your mouth feeling fresh, explore our dry mouth options.

Loss of appetite

GLP-1 medications work by mimicking the natural hormone that regulates your hunger and satiety cues. Sending the brain signals that you are fuller sooner, with less calories needed and with food emptying from the stomach slower, reducing your appetite. This is one of the key mechanisms behind how these weight loss injections work. 

• Have smaller, more frequent and highly nutritional meals

• Consider a meal time to plan a consistent food intake

• Try and eat, especially if you're losing too much weight as this can cause other medical issues

If you find that your weight loss is too rapid or causing health or energy issues, talk to your doctor. Your dosage could be too high or it could be a sign of something more serious.

Rare and long-term weight loss injection side effects

There are some rare but potentially serious weight loss injection side effects. While most people will not encounter these side effects, it’s important to be aware of them so you can spot the signs early and get the right help if needed.

Some of these side effects may require medical attention, especially if symptoms are sudden, severe or don’t go away. If you’re ever unsure, it’s always best to speak with your doctor, pharmacist or contact the non-emergency medical services.

Acute pancreatitis

The pancreas has two main jobs; to create digestive enzymes that break down all food and to produce hormones to maintain sugar levels. When the pancreas is inflamed, it produces and activates digestive enzymes too early. This leads to damage and swelling in the pancreas, triggering an immune response resulting in symptoms such as:

• Sudden and severe abdominal pain that can spread to the back

• Vomiting

• Nausea

• Fever: temperature being 38°C or more

• Fast heart rate accompanied by rapid breathing 

• Jaundice: yellowing of the skin and whites of the eyes

When to act:

Urgent medical attention is required for severe, persistent abdominal pain (with or without vomiting). Stop the medicine and contact a clinician immediately.

If you notice less serious symptoms, seek medical advice from your doctor or contact non-emergency services.

Gallbladder issues

The gallbladder is a small organ located underneath the liver. The main job is to store and release bile, a digestive fluid that helps to break down fats. Gallstones, while painful and often have no symptoms. They are small stones produced by a build up of cholesterol and bile. On occasion these gallstones can block the bile ducts, causing inflammation and pain (acute cholecystitis.)

Acute cholecystitis is potentially serious due to the complication risk associated. The main symptoms is sudden sharp pain located in the upper right hand side of the abdomen, that spreads towards your right shoulder. Unlike other abdominal pain, the pain of acute cholecystitis will not go away after a few hours.

Other symptoms to look out for include:

• Fever (temperature of 38°C or higher)

• Jaundice: yellowing of the skin or whites of the eyes

• Bloating

• Indigestion

• Nausea

• Vomiting

When to act:

Seek urgent medical attention if you have a sharp or persistent pain in the upper right abdomen, especially after eating. Or if it’s accompanied by nausea, vomiting, fever or jaundice.

If symptoms are milder or occasional, speak to your doctor or contact the non-emergency medical service for advice.

Low blood sugar (Hypoglycaemia)

Your body relies on sugar (glucose) in the blood for energy, especially for your brain and muscles. We get most of this energy from carbohydrates, which the body breaks down into glucose. When you’re taking a GLP-1 medication, your appetite often decreases, which means you may eat less and take in fewer carbohydrates. As a result, the amount of readily available glucose in your body can drop.

When your blood sugar drops too long, it becomes a problem, as the body can't function correctly. Leading to symptoms that affect your brain and nervous system:

• Increased hunger

• Dizziness

• Anxiousness or irritability 

• Shakiness or trembling

• Sweating

• Feeling weak or tired

• Heart palpitations 

• Feeling confused

• Blurred vision

If your blood sugar is severely low, you can experience: 

• Having fits or seizures

• Unconsciousness

When to act:

If someone has severely low blood sugar:

1. Put them into recovery position

2. Give them a glucagon injection. If they respond within 10 minutes and can swallow, give them food and fluids to raise their blood sugar levels.

3. If they don't have a glucagon injection or you don't know how to use it, seek urgent medical attention

To raise low blood sugar, eat or drink something sugary immediately such as a glass of juice, glucose tablets or sweets.

If symptoms don’t improve within 10-15 minutes or become more serious, seek urgent medical attention. Always speak with your doctor if you experience frequent episodes of low blood sugar, as your medications may need adjusting.

Kidney problems

Your kidneys filter waste, balance fluids and help control blood pressure. While taking GLP-1 medications, it can contribute to 2 types of kidney issues.

 Acute kidney injury

Is the sudden decline in kidney function that can happen over hours or days. Most cases are caused through a reduced blood flow to the kidneys and can cause sepsis. Other reasons include inflammation of the kidney filters (glomerulonephritis) or the blood vessels (vasculitis) or other kidney structures. This means that the kidneys can no longer effectively filter waste or maintain fluid and electrolyte balance. 

While GLP-1 medications don’t directly cause acute kidney injury, they can contribute to it, especially if you become dehydrated from ongoing nausea, vomiting or diarrhoea. People without a history of kidney problems can still be affected, particularly if they’re unable to maintain proper fluid intake during treatment. Signs to look out for include:

• Reduced urination or very dark urine

• Dehydration

• Downiness

• Fatigue or weakness

• Diarrhoea

• Nausea or vomiting

• Confusion

When to act:

If you notice a sudden drop in urine output, feel dehydrated or experience ongoing vomiting, diarrhoea or confusion, contact your doctor immediately. These may be early signs of acute kidney injury, which can often be reversed with quick treatment.

Without quick treatment, electrolyte levels and waste can build up in the body, affecting how other organs function. Even if it doesn’t lead to complete kidney failure, acute kidney injury is a serious condition and should always be treated as a medical concern.

Chronic Kidney Disease

It’s a long term condition where the kidneys gradually lose their ability to function the way they used to. Chronic kidney disease develops over time and is often linked to underlying conditions like diabetes, high blood pressure or prolonged use of certain medications.

If you have reduced kidney function, taking GLP-1 medications will only worsen the condition or speed it up with side effects like dehydration. Some signs that the condition has progressed include:

Signs of worsening chronic kidney disease may include:

• Blood in urine

• Nausea 

• Tiredness

• Shortness of breath

• Swelling in the ankles, feet or hands

When to act:

If you notice blood in your urine, contact your doctor immediately. If your other symptoms persist, speak to your doctor, especially if you have a history of kidney issues.

Severe allergic reaction (Anaphylaxis)

Anaphylaxis is a rare but serious allergic reaction that can happen suddenly and requires immediate medical attention. It can occur after taking any medication and is one of the rarest weight loss injection side effects. 

Anaphylaxis affects multiple systems in the body, including the skin, airways and cardiovascular system. Symptoms may include:

• Swelling of the throat, face, lips or tongue

• Difficulty swallowing, hoarse voice or tightness in the throat

• Difficulty breathing or fast and shallow breathing

• Wheezing or coughing

• Rapid heart rate

• Tightness in the chest

• Feeling faint, dizzy, tired or confused

• A swollen rash that is raised and/or very itchy

• Skin that is cold to the touch

• Change in the skin colour, particularly around the mouth. If you have brown or black skin, this is easier to see on the palms of your hands or soles of your feet

When to act:

If you suspect you or someone else is having an allergic reaction with difficulty breathing, swelling or fainting, call 999 immediately.

If you have a prescribed adrenaline auto-injector, such as an EpiPen, do not wait. Use it straight away while you wait for help. Anaphylaxis can worsen quickly as it’s a medical emergency.

When to seek medical advice for GLP-1 side effects

Most weight loss injection side effects are mild and temporary, especially when starting treatment or increasing your dosage. For some people, these side effects can begin to impact their daily lives and this is when it's important to seek medical advice from a doctor, pharmacist or non-emergency medical services. 

You should seek medical advice if you experience any of the following:

• GLP-1 side effects that are severe, not improving, lasting longer than expected or continue to get worse over time

• You're struggling to stay hydrated due to continued vomiting, diarrhoea or loss of appetite

• You notice new or unusual side effects, such as severe stomach pain, yellowing of the skin or eyes (jaundice) or persistent fatigue

• You have signs of low blood sugar, especially if you take diabetic medication

• You feel confused, faint or unusually unwell

• You suspect an allergic reaction, with symptoms such as difficulty breathing, swelling of the face or throat or a very itchy rash

If you're unsure about your side effects, it's better to contact your doctor or pharmacist, as you don't need side effects to be severe to ask for advice. Early advice can help to prevent complications and keep your treatment plan on track.

Where to report side effects

In the UK, there is one body that you can use to report weight loss injection side effects or any other medications. It's the Yellow Card website and the schema is run by the Medicines and Healthcare products Regulatory Agency (MHRA). 

They are responsible for collecting and monitoring information about the safety and quality of healthcare products. Ranging from medicines, vaccines, medical devices, blood products and e-cigarettes.

Why report weight loss injection side effects?

Everyone has different genetics, tolerances and medical histories, making it difficult to know if you will experience a side effect when starting a new medication. Your reports help regulators monitor medicine safety and update guidance where needed.

How to manage GLP-1 side effects

Coping with GLP-1 side effects is about listening to your body, making gradual lifestyle changes and seeking support when needed. Most symptoms ease over time as your body adjusts to the medication.

Managing the weight loss injection side effects are often the same when starting treatment or increasing the dose. Here are five key areas to focus on:

1. Start with a low dose and slowly increase

GLP-1 medications are started at the lower dosage to reduce and prevent as many unwanted side effects. As you increase dosage, it does increase the chances of GLP-1 side effects but by not rushing the process, it allows the body time to adjust. This can significantly reduce symptoms  such as nausea, diarrhoea and vomiting.

If you find your symptoms are lasting longer or are severe, speak to your doctor. They can keep the dosage stable to give your body extra time to adjust.

 2. Eat small, balanced meals

The food from your stomach will move out slower than it used to and you'll have other digestive changes. A way to reduce the stress on your digestive system and to help everything move is to focus on:

• Eating smaller meals

• Prioritising a balanced meal, with protein, complex carbohydrates and a variety of fruit or vegetables

• Avoiding high fat, high sugar or spicy foods that can upset your stomach

Some people found that eating bland foods reduced some of their symptoms until they disappeared. If you are unsure on what to eat, our pharmacy team can help or take a look at our nutrition guides for helpful tips.

3. Use digestive support

GLP-1 medication affects the digestive system and causes side effects like bloating, heartburn or constipation. While these are common, many people find relief with gentle digestive support, such as:

• Probiotics to support gut health

• Over the counter remedies such as fibre supplements or antacids 

• Light exercise such as yoga or walking after meals to help with digestion

• Herbal teas with peppermint or ginger

If you find your weight loss injection side effects are persistent, speak to a pharmacist or your doctor.

GLP-1 medication affects the digestive system and causes side effects like bloating, heartburn or constipation. While these are common, many people find relief with gentle digestive support, such as:

• Probiotics to support gut health

• Over the counter remedies such as fibre supplements or antacids 

• Light exercise such as yoga or walking after meals to help with digestion

• Herbal teas with peppermint or ginger

If you find your weight loss injection side effects are persistent, speak to a pharmacist or your doctor.

4. Stay well-hydrated

It's important to maintain good hydration levels, as the weight loss injections have multiple side effects that impact the body's hydration levels. From side effects that cause loss of fluids (vomiting, diarrhoea or constipation) to feeling fuller and not wanting to drink as much can lead to dehydration and make you feel even worse. 

There are tips to help your hydration levels:

• Sip water throughout the day

• Keep track of your water consumption, try to increase it each day until you reach sufficient hydration levels

• Try electrolyte drinks or rehydration sachets if needed

• Avoid caffeine or alcohol, especially in the summer, as it can worsen dehydration

Keeping your hydration levels up can reduce some of the side effects such as headaches, tiredness and dry mouth.

 5. Give your body time to adjust

Most of the weight loss injection side effects are worst at the beginning of the treatment or straight after a dosage increase. It can take a few days to a few weeks of the symptoms to reduce. 

Be patient and give your body time to adjust. Rest when you need to, take care of yourself and reach out for support. If you find your symptoms aren't improving, contact us, so we can give you the support and advice you need.