Common Side Effects
The SURMOUNT-1 clinical trial reported the following common side effects. These are typical of GLP-1 receptor agonist medications and usually improve as your body adjusts over the first 4–8 weeks.
Most common. Usually mild and worst during dose escalation.
Often settles within the first few weeks of each dose level.
Expected therapeutic effect rather than a true side effect.
More common during dose increases. Eating smaller meals helps.
Staying hydrated and increasing fibre intake can help.
Usually mild. Severe pain requires immediate attention.
Mild redness or itching. Rotating injection sites helps.
May occur during initial adjustment or with reduced calorie intake.
Serious Side Effects
While rare, some serious side effects have been associated with tirzepatide and other GLP-1 medications. The MHRA has issued guidance on the following risks:
Acute pancreatitis
Severe, persistent abdominal pain that may radiate to the back. Seek immediate medical attention. Treatment should be discontinued if pancreatitis is confirmed.
Gallbladder problems
Rapid weight loss can increase the risk of gallstones. Symptoms include severe pain in the upper right abdomen, nausea, and jaundice.
Severe gastrointestinal events
In rare cases, severe or persistent vomiting or diarrhoea can lead to dehydration and acute kidney injury. Seek help if you cannot keep fluids down.
Psychological effects
The MHRA is monitoring reports of mood changes, anxiety, and suicidal thoughts. A causal link has not been established. Report any significant mood changes to your prescriber.
Allergic reactions
Rare. Symptoms include swelling of the face, lips, tongue, or throat, difficulty breathing, or severe rash. Seek immediate emergency care.
When to Call 999
Seek emergency help for severe abdominal pain, signs of allergic reaction (swelling, difficulty breathing), severe dehydration, or thoughts of self-harm.
Managing Side Effects
Most gastrointestinal side effects can be managed with simple lifestyle adjustments:
- Eat smaller, more frequent meals throughout the day
- Avoid greasy, fried, or very rich foods — especially during dose escalation
- Stay well hydrated — aim for 2 litres of water daily
- Eat slowly and stop as soon as you feel satisfied
- Ginger tea or peppermint can help with mild nausea
- Increase fibre gradually to help with constipation
- Speak to your prescriber about adjusting the rate of dose escalation if side effects are troublesome