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
Injectable Weight Loss Treatments and Contraception
Oral Contraception and Mounjaro
If you are using oral contraception (i.e. the combined pill or the progestogen-only pill) and taking Mounjaro
(Tirzepatide), it is important to use an additional barrier method of contraception (e.g. condoms) alongside
oral contraceptive pills for 4 weeks after starting the medication and for 4 weeks after any increase in the
Mounjaro dose. You could also consider switching to long-acting contraceptives (e.g. IUD) while taking
Mounjaro.
Please note: Diarrhoea and vomiting are common side effects of Mounjaro that can reduce the
effectiveness of oral contraceptives. If vomiting occurs within three hours of taking the contraceptive
pill, or if you experience severe diarrhoea for more than 24 hours, you should follow the missed pill rules
as instructed in the patient information leaflet of your oral contraception. You should also consider an
alternative non-oral method of contraception (e.g. IUD or condoms) if your diarrhoea or vomiting persists.
Oral Contraception and Wegovy
There is currently no evidence that Wegovy (Semaglutide) can reduce the effectiveness of oral contraception
(i.e. the combined pill or the progestogen-only pill).
Please note: Diarrhoea and vomiting are common side effects of Wegovy that can reduce the
effectiveness of oral contraceptives. If vomiting occurs within three hours of taking the contraceptive
pill, or if you experience severe diarrhoea for more than 24 hours, you should follow the missed pill rules
as instructed in the patient information leaflet of your oral contraception. You should also consider an
alternative non-oral method of contraception (e.g. IUD or condoms) if your diarrhoea or vomiting persists.
Non-Oral Contraception and Mounjaro/Wegovy
There is currently no evidence that injectable weight loss treatments like Mounjaro or Wegovy can affect the
effectiveness of non-oral methods of contraception (e.g. the coil, implant, injection, patch or ring).
Therefore, there are no extra precautions that are needed when using these methods of contraception
alongside injectable weight loss treatments like Mounjaro or Wegovy.
Contraception and Switching From Wegovy to Mounjaro
If you are switching from Wegovy (Semaglutide) to Mounjaro (Tirzepatide), it is important to use an
additional barrier method of contraception (e.g. condoms) for 4 weeks after switching to Mounjaro and for 4
weeks after any increase in the Mounjaro dose, while also continuing your oral contraception. You could also
consider switching to long-acting contraceptives (e.g. IUD) while taking Mounjaro.
Oral Emergency Contraception and Mounjaro/Wegovy
It is currently unknown whether oral emergency contraception is affected by injectable weight loss treatments like Mounjaro or Wegovy. The copper IUD (coil) is the most effective method of emergency contraception that is not affected by diarrhoea and vomiting - common side effects associated with taking injectable weight loss treatments. If you require emergency contraception, please consult with your healthcare practitioner about all other medications you are taking, including injectable weight loss treatments.
Injectable Weight Loss Treatments and Pregnancy
Injectable weight loss treatments like Mounjaro or Wegovy should not be used in pregnancy. Therefore,
it is important to use effective contraception while taking injectable weight loss treatment. If you become
pregnant whilst taking Monjaro or Wegovy, it is important to consult with your doctor immediately.
If you are planning to conceive, it is important to stop taking Wegovy at least two months prior and Mounjaro at least one month prior to the planned conception
Injectable Weight Loss Treatments and Depression/Suicidal Thoughts
There is currently no evidence of a causal association between injectable weight loss treatments like
Mounjaro or Wegovy and depression, suicidal ideation and suicide.