All prescription medications, including Wegovy and Mounjaro, can cause side effects. Most side effects happen when you first start the medication or increase your dose, and usually improve on their own over time.

Below, our clinical experts have prepared some practical tips to help you handle these symptoms comfortably at home.

We’ve also included guidance on when to contact your prescriber or seek more urgent medical attention so you can stay informed and confident in managing your treatment.

Feeling sick (nausea)

This is a very common side effect and can occur in more than 1 in 10 people taking Mounjaro or Wegovy. You’re most likely to experience feeling sick when you first start your medication and when you increase your dose.

Here’s what we recommend to help you:

• Drink plenty of fluids (cold water, herbal teas)
• Get lots of fresh air
• Eat small and frequent meals
• Reduce intake of foods high in sugar and fat
• Avoid cooking or eating strong smelling foods

Need Extra Support? 

Most people can manage nausea on their own using the tips above. If you need more help or want advice about anti-sickness medication, we’re here to support you—just reach out to our clinical team. 

Vomiting

This is a very common side effect and can occur in more than 1 in 10 people taking Mounjaro or Wegovy. You’re most likely to experience vomiting when you first start your medication and when you increase your dose.

Here’s what we recommend to help you:

• Stay hydrated by taking small sips of water. You could also try herbal teas such ginger and peppermint
• Eat small and frequent meals to keep your energy levels up. Stick to a bland diet that is easy on your stomach, including toast, rice and bananas

Need Extra Support? 

Many people find they can manage mild vomiting on their own using the tips above. 

However, if you’d like to discuss your symptoms in more detail, or seek advice on anti-sickness medication or over the counter antacids that might help, our clinicians are  here to support you. Please contact us here. 

Contact your GP or call 111 if:

• You have been vomiting for more than a couple of days
• You have signs of dehydration (dark urine, or peeing less than usual)

Make sure you inform your healthcare provider you have been taking weight loss medication.

If you are using oral contraception and have experienced vomiting within 3 hours of taking an oral contraceptive pill, you may need a repeat dose of your pill to avoid an unwanted pregnancy. You should contact your GP or call 111 for medical advice.

Call 999 or go to A&E if:

• Your vomit looks like coffee granules 
• Your vomit contains blood
• You have a fever alongside your vomiting 
• You have sudden or severe stomach pain alongside your vomiting
• You are vomiting 3 times or more per day

Make sure you tell them you have been taking weight loss medication and please inform your MedExpress clinical prescriber via email.

Diarrhoea

This is a very common side effect and can occur in more than 1 in 10 people taking Mounjaro or Wegovy. You’re most likely to experience diarrhoea when you first start your medication and when you increase your dose.

Here’s what we recommend to help you:

• Drink plenty of fluids (water, herbal teas)
• Eat small and frequent meals
• Rest – take it easy and allow your body to recover
• Consider taking oral rehydration salts from a pharmacist to replace lost fluids and electrolytes
• Paracetamol for pain relief

Need Extra Support? 

Many people find that they can manage mild diarrhoea on their own using the provided advice. However, if you’d like to discuss this symptom in more detail, or seek advice on oral rehydration salts, we’re here to support you—just reach out to our clinical team.

Contact your GP or call 111 if:

• Diarrhoea lasts for more than a week
• Your poo contains blood
• You have signs of dehydration (dark urine, peeing less than usual). 

Make sure you inform your healthcare provider you have been taking weight loss medication.

If you are using oral contraception and have experienced diarrhoea that has lasted for over 24 hours, you may need a repeat dose of your pill to avoid an unwanted pregnancy. You should contact your GP or call 111 for medical advice.

Call 999 or go to A&E if you have diarrhoea and:

• You have sudden or severe stomach pain
• You are experiencing a high fever or chills

Make sure you tell them you have been taking weight loss medication and please inform your MedExpress clinical prescriber via email.

Constipation

This is a very common side effect and can occur in more than 1 in 10 people taking Mounjaro or Wegovy. You’re most likely to experience constipation when you first start your medication and when you increase your dose.

Here’s what we recommend to help you:

• Drink plenty of fluids (water, herbal teas)
• Eat high-fibre foods such as prunes, figs, and oats 
• Take regular walks – exercise can stimulate bowel movements.
• Consider glucomannan supplements – glucomannan is a water soluble fibre that softens stools to make them easier to pass. It can also help with regular bowel movements 

Need Extra Support?

Many people find they can manage constipation on their own using the tips above. If you need more help or want advice about laxatives or supplements, we’re here to support you—just reach out to our clinical team. 

Contact your GP if:

• Your constipation does not improve even after following the advice above
• You notice blood in your poo

Make sure you inform your healthcare provider you have been taking weight loss medication.

Headache

This is a very common side effect and can occur in more than 1 in 10 people taking Wegovy. You’re most likely to experience headaches when you first start your medication and when you increase your dose.

Here’s what we recommend to help you:

• Drink plenty of fluids (water, herbal teas)
• Use simple pain relief like paracetamol
• Apply a hot or cold compress
• Ensure you are getting enough sleep – aim for 7-9 hours a night

Need Extra Support? 

Many people find they can manage mild headaches on their own using the tips above. However, if you’d like to discuss how to manage your headache in more detail, or seek advice on pain relief, we’re here to support you—just reach out to our clinical team.

Contact your GP or call 111 if:

• Your headache lasts for more than a few days
• Your headache gets progressively worse
• You notice changes in vision
• You have other symptoms like vomiting or dizziness.

Make sure you inform your healthcare provider you have been taking weight loss medication.

Stomach pain

This is a very common side effect and can occur in more than 1 in 10 people taking Mounjaro or Wegovy. You’re most likely to experience stomach pain when you first start your medication and when you increase your dose. 

How you manage the pain depends on the type you’re experiencing:

Trapped wind

Usually feels like bloating or pressure in your stomach, sometimes with burping or gas. To ease trapped wind:

• Eating small and frequent meals
• Chewing food slowly with your mouth closed
• Going for a walk
• Drinking peppermint tea

Heartburn 

Typically feels like a burning sensation behind your breastbone or a sour taste in your mouth. To reduce heartburn:

• Reducing your caffeine intake
• Don’t eat too close before you go to bed
• Avoid rich, spicy, or fatty foods

Need Extra Support? 

Many people find they can manage mild stomach pain on their own using the tips above. However, if you’d like to discuss your symptoms in more detail, or seek advice on heartburn medication, we’re here to support you—just reach out to our clinical team.

Call 999 or go to A&E if your stomach pain becomes severe. Severe means:

• It’s so intense (around 8 or more out of 10) that you can’t focus on anything else
• It makes it nearly impossible to handle normal daily tasks (like walking, getting dressed, or eating)
• It doesn’t improve with over-the-counter pain relief or rest
• It radiates to your back or underneath your right ribcage or your right shoulder 
• You also have severe vomiting (3 or more times in a day)

Make sure you tell them you have been taking weight loss medication and please inform your MedExpress clinical prescriber via email.

Injection site reaction

This is a common side effect and can occur in up to 1 in 10 people taking Mounjaro or Wegovy.

Here’s what we recommend to help you:

• Rotate your injection site each week. You can alternate between different areas such as your lower stomach, thigh, arm, and buttocks. This helps prevent irritation. 
• Make sure you’re correctly injecting your medication

For Wegovy, see the correct injection technique here.

For Mounjaro, see the correct injection technique here.

Need Extra Support? 

Many people find they can manage mild injection site reactions on their own using the tips above. However, if you’d like to discuss managing your symptoms in more detail, or seek advice on injecting your medication properly,  we’re here to support you—just reach out to our clinical team.

Contact your GP or call 111 if:

• You notice intense redness around the injection site
• You notice a rash that worsens or spreads around the injection site 
• You notice warmth or pus at the injection site
• You also have a fever or chills

Make sure you inform your healthcare provider you have been taking weight loss medication.

When to Seek Urgent Help 

Call 999 or go to A&E if you experience difficulty breathing, or swelling of the lips, tongue, or throat. These could be signs of a severe allergic reaction (also called anaphylaxis), which can be life-threatening. 

Fatigue

Fatigue is a very common side effect of Wegovy, affecting more than 1 in 10 people, while it is common with Mounjaro, occurring in up to 1 in 10 people.

Here’s what we recommend to help you:

• Make sure you are eating enough nutrient-dense food to get the calories you need for energy
• Ensure you are getting enough vitamins. For example, vitamin B12 (found in meat, fish, cheese and eggs) is important for energy production. Low vitamin D levels are also linked to fatigue, and while sunlight is the best source of this vitamin (we recommend that you always wear factor 50SPF sunscreen), it is also found in oily fish, red meat, liver and egg yolks
• Check your iron levels, as low levels can cause fatigue. Iron is found in liver, red meat, and beans such as red kidney beans, edamame beans and chickpeas
• Exercise regularly to boost energy
• Try to stick to the same sleep schedule and aim for 7 to 9 hours of sleep a night.
• Have a relaxing sleeping area (not too bright, noisy or warm)

Need Extra Support? 

Many people find they can manage mild fatigue on their own using the provided advice. However, if you’d like to discuss your symptoms in more detail, or seek advice on vitamin supplementation or advice on lifestyle changes, we’re here to support you—just reach out to our clinical team.

Dizziness

This is a common side effect and can occur in up to 1 in 10 people taking Mounjaro or Wegovy.

Here’s what we recommend to help you:

• Drink plenty of fluids (water, herbal teas)
• Lie down until the dizziness passes
• Move carefully and slowly
• Get plenty of rest
• Avoid coffee, cigarettes and alcohol

Need Extra Support? 

Many people find they can manage mild dizziness on their own using the provided advice. However, if you’d like to discuss managing your symptoms in more detail, or seek advice on medication for dizziness, we’re here to support you—just reach out to our clinical team.

When to Contact Your GP or call 111

• You’re having trouble hearing or speaking
• You’re hearing ringing in your ears
• You experience vision changes
• You lose consciousness or faint 

Make sure you inform your healthcare provider you have been taking weight loss medication.

When to Seek Urgent Help 

Call 999 or go to A&E if you experience dizziness and your face, arms or legs feel numb or weaker than usual.

Hair loss

This is a common side effect and can occur in up to 1 in 10 people taking Mounjaro or Wegovy.

Losing 50 to 100 hairs a day is normal and often goes unnoticed. Hair loss while using Mounjaro or Wegovy is typically due to telogen effluvium – a temporary condition triggered by rapid weight loss. 

Once your weight stabilises, this side effect usually subsides and your hair should regrow to its original thickness.

Here’s what we recommend to support hair health:

• Aim for a gradual and steady weight loss of 0.5-1kg per week to reduce stress on your body.
• Ensure your diet includes sufficient amounts of protein, iron, zinc, and B vitamins (like biotin), which are essential for hair growth.
• Manage stress, as high stress levels can disrupt hair follicle function. Focus on relaxation techniques like meditation, gentle exercise, or breathing exercises.

Need Extra Support? 

Most hair loss in this case is temporary, and your hair is likely to grow back. 

However, if you’d like to discuss hair loss in more detail, we’re here to support you—just reach out to our clinical team.

Gallstones

The gall bladder is a pear shaped organ that sits near your right ribcage. 

Gallstones don’t usually cause any symptoms, and many people don’t realise they have them.

Gallstones are a common side effect that can happen with rapid weight loss. Up to 1 in 10 people using Wegovy may develop gallstones, and up to 1 in 100 using Mounjaro. 

If you have gallstones, you can still use medications like Mounjaro and Wegovy. During your consultation, we’ll take all factors into account to see if these options are right for you.

 Call 999 or go to A&E if:

• You have severe pain under your right ribcage that extends to your right shoulder or back that disrupts your normal daily activities (possible acute gallbladder disease).
• The pain is accompanied by 
  • Vomiting
  • High temperature
• A rapid heartbeat 

Be sure to mention you’re on weight loss medication and notify your MedExpress clinical prescriber by email.

Changes in taste

This is a common side effect of Wegovy, affecting up to 1 in 10 people, but it is uncommon with Mounjaro, occurring in fewer than 1 in 100 people.

The medical term for changes in taste is ‘dysguesia’. Dysgeusia isn’t a serious medical condition, but it can impact appetite. Common symptoms include:

• A persistent metallic or bitter taste in all foods
• Sweet or salty foods lose their usual flavor
• Foods that once tasted good now seem unpleasant
• A lingering bad taste in the mouth, even without eating anything

Researchers are still exploring why some people experience taste disturbances while taking weight loss medication. 

Here’s what we recommend for ‘dysguesia’:

• Change up your food choices by eating citrus fruits, vinegar and pickles. Avoid very sweet or spicy foods.
• Drink plenty of water to prevent a dry mouth
• Switch from metal utensils to plastic or ceramic
• Brush and floss your teeth regularly 
• Avoid smoking

Need Extra Support? 

If you’d like to discuss changes in taste in more detail, our clinicians are available to assist you. Please contact us for support if needed – we’re here to help.

Heart Palpations

This is an uncommon side effect of Wegovy and Mounjaro, affecting less than 1 in 100 people. An increased heart rate may present as a “fast pulse” or racing heartbeat at rest.

Researchers are still exploring why some people experience an increased heart rate while taking weight loss medication, but here are some tips to help you manage it:

Monitor Your Heart Rate

• Keep track of your resting heart rate, either manually or by using a smartwatch/fitness tracker.
• Note any episodes of palpitations (an unusual awareness of your heartbeat).

Reduce Triggers

• Cut back on or avoid caffeine, alcohol, and smoking—all of which can raise heart rate.

Need Extra Support?

 If you’d like to discuss your symptoms in more detail, our clinicians are available to help—just reach out by email.

Contact your GP or call 111 if:

• You notice repeated palpitations (racing or pounding heartbeat) that keep coming back or worsen.
• You have a history of heart problems in your family.

Make sure you inform your healthcare provider you have been taking weight loss medication.

Low blood sugar (hypoglycaemia)

Low blood sugar is an uncommon side effect of Wegovy and Mounjaro, affecting fewer than 1 in 100 people without type 2 diabetes.

It’s more likely to affect people who have type 2 diabetes, particularly those taking other medications such as insulin that lower blood sugar levels.

Common symptoms of low blood sugar include:

• Feelings of hunger, dizziness, confusion, tiredness, or weakness
• Mood changes such as anxiety or irritability
• Sweating
• Shaking
• Tingling lips
• Heart palpitations
• Changes in vision including blurred vision

When to Contact Your GP or call 111

If you experience any of the above symptoms you should call 111 immediately. Have something sugary straight away – like fruit juice, a fizzy drink, glucose tablets or sweets. Once you start feeling better, follow up with something longer-lasting, like a slice of bread or some biscuits, to help keep your blood sugar steady.

If you’re having low blood sugar episodes often, it’s important to speak to your GP. Make sure you tell them you have been taking weight loss medication and please inform your MedExpress clinical prescriber via email.

When to Seek Urgent Help

In rare cases, you could lose consciousness if your blood sugar drops too low. This is a medical emergency. If you think someone has very low blood sugar and they are not responding normally, call 999 or go to A&E.

When to Seek Urgent Medical Help

Call 999 or go to A&E immediately if you experience:

• Severe vomiting (3 times or more in one day) and/or:
  • Your vomit looks like coffee granules
  • Your vomit contains blood
  • You have a fever alongside your vomiting
• Severe stomach pain. Severe means:
  • It’s so intense (around 8 or more out of 10) that you can’t focus on anything else
  • It makes it nearly impossible to handle normal daily tasks (like walking, getting dressed, or eating)
  • It doesn’t improve with over-the-counter pain relief or rest
  • It radiates to your back or underneath your right ribcage or your right shoulder 
  • You also have severe vomiting (3 or more times a day)
• Severe pain underneath your right ribcage that may spread to your shoulder or back, especially if you also have:
  • Vomiting
  • A high temperature
  • A rapid heartbeat

• Dizziness and your face, arms or legs feel numb or weaker than usual
• Difficulty breathing, or swelling of the lips, tongue, or throat

• Signs of very low blood sugar in someone who is unresponsive or not behaving normally, including:
  • Dizziness
  • Irritability
  • Confusion
  • Rapid heartbeat
  • Sweating

Cancer concerns: understanding the risks

GLP-1 medications carry a potential risk of thyroid C-cell tumours, including medullary thyroid carcinoma (MTC). This risk is based on studies in rodents, and has not been observed in human studies.

Recent research has shown that there is no link between GLP-1 medication use and increased thyroid cancer risk in humans.

However, current guidance is that patients with a personal or family history of any thyroid cancer (including  MTC or Multiple Endocrine Neoplasia syndrome type 2 (MEN2)) should not be prescribed GLP-1 medications.

How long will side effects last with Mounjaro/Wegovy?

Everyone responds differently to weight loss medications like Mounjaro and Wegovy, so the timeline for experiencing side effects can vary from person to person.

It’s common to notice some side effects when you first start taking these medications or after an increase in your dosage. This happens because your body is adjusting, and these side effects usually subside within a few days to a couple of weeks. Most people find these temporary issues manageable at home with simple care strategies.

If your side effects last longer, worsen, or significantly impact your comfort, it’s important to discuss this with our clinical team. You can contact them by email here. 

We’ve clearly outlined specific symptoms that require you to contact your GP, call NHS 111, or seek emergency care immediately by calling 999.

Will side effects get worse when I increase the dose?

When you increase your dose, side effects can sometimes return or feel more intense. This is completely normal, as your body needs time to adapt to the higher dose. The good news is these symptoms typically ease as your body adjusts, usually within a few days or weeks.

If you’re concerned about increasing your dose or experiencing side effects, our clinical team is here to support you – contact us here.

I want to contact a member of the clinical team regarding my symptoms

You can contact a member of the clinical team here.