Answers
Weight-loss injections (semaglutide, tirzepatide): what do they do to the gut?
Short answer
Medicines such as semaglutide and tirzepatide (GLP-1 medicines) slow stomach emptying and reduce appetite. They help weight, diabetes and fatty liver, but often cause nausea, fullness, constipation or loose motions, especially when the dose goes up. Rarely, they can trigger gallstones or pancreatitis. Use them only under a doctor's care.
Common gut side effects
These are usually mild and settle over a few weeks. They are worse when the dose is increased too quickly.
- Nausea, early fullness, burping and bloating
- Constipation or loose motions
- Vomiting, usually after large or fatty meals
Less common but important
- Gallstones and gallbladder pain, partly from rapid weight loss
- Pancreatitis: severe upper belly pain spreading to the back, with vomiting; stop the medicine and get emergency care
- Dehydration from vomiting or loose motions, which can affect the kidneys
- Muscle loss if protein intake is too low
Before an endoscopy or surgery
Because these medicines slow stomach emptying, food can stay in the stomach longer than usual. Always tell your doctor and anaesthetist that you take them. You may be asked to take only liquids the day before, or to adjust the timing of the injection.
Using them safely
- Only on a doctor's prescription, never from gyms or unverified online sellers
- Keep follow-up visits to check weight, sugar, liver and side effects
- They work best with diet and exercise changes, which help keep the weight off if the medicine is stopped
- They are not suitable for everyone, including pregnant women and people with certain thyroid tumours or past pancreatitis; your doctor will check
Eating while on weight-loss injections
Eat more
- Small meals, eaten slowly; stop as soon as you feel full
- Protein at every meal: dal, paneer, curd, eggs, fish or chicken, to protect muscle
- Fibre and plenty of water to prevent constipation
Cut down
- Fried, fatty and very sweet foods, which worsen nausea
- Large meals and lying down soon after eating
- Alcohol
Good to know
- Strength exercise two or three times a week helps keep muscle while losing weight.
- If you cannot keep fluids down, contact your doctor; dehydration can harm the kidneys.
Common questions
Will the weight come back when I stop?
Often, some of it does, especially without lasting changes in diet and activity. Plan with your doctor how long to continue.
Can I take them for fatty liver?
They can reduce liver fat and help some people with fatty liver, especially with diabetes or obesity. Your doctor decides if they suit you.
Is nausea a reason to stop?
Mild nausea usually settles. Severe or persistent vomiting, or severe belly pain, needs your doctor straight away.