To use injectable weight loss medication like Mounjaro or Wegovy safely and achieve the best results, it’s important to know how to administer your weight loss injection correctly
and be aware of any potential side effects.
With that in mind, our experts have compiled important information about how to use your weight loss pen safely and how to manage common side effects.
Video Tutorials
Mounjaro Treatment Tutorial
Find out everything you need to know about how to safely use and store Mounjaro with this comprehensive guide to the treatment.
Wegovy Treatment Tutorial
Find out everything you need to know about how to safely use and store Wegovy with this comprehensive guide to your treatment.
Potential Side Effects That Are Common
As with most medications, injectable weight loss treatments like Mounjaro or Wegovy may cause side effects. These side effects are often mild and tend to subside as your body
adjusts to the treatment. To help, our experts have compiled this overview with practical tips on how to manage them.
Nausea/vomiting
Nausea and/or vomiting are common side effects associated with using injectable weight loss medication that occur in approximately 1 in 10 individuals, particularly during dose
escalation.
Tips to manage nausea and/or vomiting:
- Stay Hydrated: Drink plenty of clear fluids such as water or herbal teas.
- Eat Small, Frequent Meals: Eating your meals in smaller, more frequent portions can help reduce the side effects.
- Drink Herbal Teas: Ginger, peppermint or fennel teas can help soothe nausea.
- Avoid Strong-Smelling Foods: Strong odours can trigger or worsen nausea.
- Get Fresh Air: A short walk can help relieve symptoms and provide a distraction.
Vomiting more than three times a day or experiencing severe symptoms like abdominal pain may indicate that the treatment is not suitable for you.
Injectable weight loss treatments can increase the risk of dehydration due to gastrointestinal side effects commonly associated with the treatment. It is important to be aware of
dehydration symptoms like dark urine, reduced urination or lightheadedness. Make sure to drink plenty of clear fluids during the treatment and seek medical advice if these
symptoms occur.
Call NHS 111 for urgent medical advice if you are unable to retain fluids or if your symptoms become worse.
Constipation
Constipation is a common side effect associated with using injectable weight loss medication that occurs in more than 1 in 10 individuals.
Tips to manage constipation:
- Stay Hydrated: Drink plenty of clear fluids such as water or herbal teas.
- Eat High-Fibre Foods: Include foods like prunes, figs, oats and whole grains in your diet.
- Take Regular Walks: Light physical activity can stimulate bowel movements.
Headaches
Headaches are a very common side effect associated with using injectable weight loss medication that occurs in more than 1 in 10 individuals. However, they tend to improve after a
few days or weeks of the treatment.
Tips to manage headaches:
- Rest in a Quiet, Dark Environment: Lying down in a dimly lit room can reduce sensitivity to light and noise which can help ease the symptoms.
- User Relaxation Techniques: Meditation or scalp massage can help ease tension.
- Get Adequate Sleep: Aim for 7-9 hours of sleep every night.
Contact your GP or call NHS 111 if your headaches persist or worsen.
Diarrhoea
Diarrhoea is a very common side effect associated with using injectable weight loss medication, especially at the start of the treatment. However, the symptoms tend to improve
after a few doses of the treatment.
Tips to manage diarrhoea:
- Stay Hydrated: Drink plenty of clear fluids like water or herbal teas.
- Get Plenty Of Rest: Allowing your body time to rest can help ease the symptoms.
Contact NHS 111 if your diarrhoea persists for more than a few days, if you are unable to tolerate or retain fluids, if you feel excessively drowsy or if you notice blood in your
stools or rectal bleeding.
Heartburn
Heartburn is a common side effect associated with using injectable weight loss medication and is often paired with nausea.
Tips to manage heartburn:
- Stay Hydrated: Drink plenty of clear fluids like water or herbal teas.
- Eat Small, Frequent Meals: Eating your meals in smaller, more frequent portions can help reduce pressure on the stomach.
- Avoid High-Fat or Sugary Foods: Foods that are high in fat or sugar can trigger or worsen heartburn.
Injection Site Reactions
Reactions like redness, itching or swelling around the injection occur in up to 1 in 10 individuals. However, these symptoms tend to improve over the course of the treatment.
Tip to manage injection site reactions:
- Rotate Injection Sites: Switching injection sites after each dose can help avoid irritation.
Discontinue the treatment and contact your GP or NHS 111 if the rash around the injection site worsens, spreads, becomes very red or causes significant pain. Please also report any
severe adverse injection site reactions to us.
Gallstones & Gallbladder Inflammation
Gallstones may occur in up to 1 in 10 individuals using Wegovy and up to 1 in 100 individuals using Mounjaro. Using injectable weight loss treatment can also increase the risk of
developing gallbladder inflammation (cholecystitis).
Seek immediate medical attention if you experience any of the following:
- Severe Abdominal Pain (especially upper right side under ribs)
- Vomiting
- Blood In Your Urine
- High Body Temperature
To reduce your risk of developing gallstones or gallbladder inflammation, maintain a steady rate of weight loss by eating small, regular meals and drinking plenty of clear fluids.
Potential Side Effects That Require Urgent Medical Attention
Although rare, some of the side effects associated with using injectable weight loss treatment require immediate medical attention.
Pancreatitis
An uncommon but serious side effect.
Call NHS 111 or go to A&E immediately if you experience:
- Severe abdominal pain radiating to your back
- Nausea or vomiting
Anaphylaxis
A rare but life-threatening allergic reaction.
Call 999 or go to A&E immediately if you experience:
- Difficulty breathing
- Swelling of your face, tongue or throat