The common effects are gastrointestinal, and they are common
Nausea, constipation, diarrhoea and indigestion are the effects reported most often. Headache, stomach pain and appetite changes also appear. For most people these are mild and ease as the body adjusts.
This is a class effect. GLP-1 medicines slow gastric emptying, which is part of how they work, and the digestive system registers that.
Severity tracks the dose, not the format
Side effects are dose dependent. They are most likely in the first weeks of treatment and in the period just after each increase. This is the entire reason both approved oral medicines use a step up schedule that raises the dose no faster than every 30 days.
A tablet is not inherently gentler than an injection. What makes treatment tolerable is the pace of escalation.
The serious ones are rare and worth knowing by name
Pancreatitis, inflammation of the pancreas, is rare but serious. Persistent severe abdominal pain is the signal to seek medical help rather than wait.
Low blood glucose can occur, and the risk rises for people also taking insulin or a sulfonylurea. GLP-1 receptor agonists also carry a thyroid tumour warning based on rodent studies, which is why personal or family history of medullary thyroid carcinoma is part of the prescribing assessment.
Why compounded and counterfeit products change this picture
Adverse event reporting for compounded semaglutide and tirzepatide runs into the hundreds of reports. Unapproved products carry risks that have nothing to do with the medicine itself: wrong ingredients, wrong strength, contamination.
Side effect information here is drawn from published trial data and regulatory material. It is not a substitute for the leaflet that comes with your medicine or for advice from your prescriber.